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CHÂTELET (from Med. Lat. castella), the word, sometimes also written castillet, used in France for a building designed for the defence of an outwork or gate, sometimes of great strength or size, but distinguished from the château, or castle proper, in being purely defensive and not residential. In Paris, before the Revolution, this word was applied both to a particular building and to the jurisdiction of which it was the seat. This building, the original Châtelet, had been first a castle defending the approach to the Cité. Tradition traced its existence back to Roman times, and in the 18th century one of the rooms in the great tower was still called the chambre de César. The jurisdiction was that of the provostship (prévôté) and viscountship of Paris, which was certainly of feudal origin, probably going back to the counts of Paris.

It was not till the time of Saint Louis that, with the appointment of Étienne Boileau, the provostship of Paris became a prévôté en garde, i.e. a public office no longer put up to sale. When the baillis (see Bailiff AND Bailie) were created, the provost of Paris naturally discharged the duties and functions of a bailli, in which capacity he heard appeals from the seigniorial and inferior judges of the city and its neighbourhood, keeping, however, his title of provost. When under Henry II. certain bailliages became presidial jurisdictions (présidiaux), i.e. received to a certain extent the right of judging without appeal, the Châtelet, the court of the provost of Paris, was made a presidial court, but without losing its former name. Finally, various tribunals peculiar to the city of Paris, i.e. courts exercising jurisdictions outside the common law or corresponding to certain cours d’exception which existed in the provinces, were united with the Châtelet, of which they became divisions (chambres). Thus the lieutenant-general of police made it the seat of his jurisdiction, and the provost of the Île de France, who had the same criminal jurisdiction as the provosts of the marshals of France in other provinces, sat there also. As to the personnel of the Châtelet, it was originally the same as in the bailliages, except that after the 14th century it had some special officials, the auditors and the examiners of inquests. Like the baillis, the provost had lieutenants who were deputies for him, and in addition gradually acquired a considerable body of ex officio councillors. This last staff, however, was not yet in existence at the end of the 14th century, for it is not mentioned in the Registre criminel du Châtelet (1389-1392), published by the Société des Bibliophiles Français. In 1674 the whole personnel was doubled, at the time when the new Châtelet was established side by side with the old, the two being soon after amalgamated. On the eve of the Revolution it comprised, beside the provost whose office had become practically honorary, the lieutenant civil, who presided over the chambre de prévôté au parc civil or court of first instance; the lieutenant criminel, who presided over the criminal court; two lieutenants particuliers, who presided in turn over the chambre du présidial or court of appeal from the inferior jurisdictions; a juge auditeur; sixty-four councillors (conseillers); the procureur du roi, four avocats du roi, and eight substituts, i.e. deputies of the procureur (see Procurator), beside a host of minor officials. The history of the Châtelet under the Revolution may be briefly told: the Constituent Assembly empowered it to try cases of lèse-nation, and it was also before this court that was opened the inquiry following on the events of the 5th and 6th of August 1789. It was suppressed by the law of the 16th of August 1790, together with the other tribunals of the ancien régime.

CHÂTELLERAULT, a town of western France, capital of an arrondissement in the department of Vienne, 19 m. N.N.E. of Poitiers on the Orleans railway between that town and Tours. Pop. (1906) 15,214. Châtellerault is situated on the right and eastern bank of the Vienne; it is connected with the suburb of Châteauneuf on the opposite side of the river by a stone bridge of the 16th and 17th centuries, guarded at the western extremity by massive towers. The manufacture of cutlery is carried on on a large scale in villages on the banks of the Clain, south of the town. Of the other industrial establishments the most important is the national small-arms factory, which was established in 1815 in Châteauneuf, and employs from 1500 to 5500 men. Châtellerault (or Châtelherault: Castellum Airaldi) derives its name from a fortress built in the 10th century by Airaud, viscount of its territory. In 1515 it was made a duchy in favour of François de Bourbon, but it was not long after this date that it became reunited to the crown. In 1548 it was bestowed on James Hamilton, 2nd earl of Arran (see Hamilton).

CHATHAM, WILLIAM PITT, 1st Earl of (1708-1778), English statesman, was born at Westminster on the 15th of November 1708. He was the younger son of Robert Pitt of Boconnoc, Cornwall, and grandson of Thomas Pitt (1653-1726), governor of Madras, who was known as “Diamond” Pitt, from the fact of his having sold a diamond of extraordinary size to the regent Orleans for something like £135,000. It was mainly by this fortunate transaction that the governor was enabled to raise his family, which was one of old standing, to a position of wealth and political influence. The latter he acquired by purchasing the burgage tenures of Old Sarum.

William Pitt was educated at Eton, and in January 1727 was entered as a gentleman commoner at Trinity College, Oxford. There is evidence that he was an extensively read, if not a minutely accurate classical scholar; and it is interesting to know that Demosthenes was his favourite author, and that he diligently cultivated the faculty of expression by the practice of translation and re-translation. An hereditary gout, from which 2 he had suffered even during his school-days, compelled him to leave the university without taking his degree, in order to travel abroad. He spent some time in France and Italy; but the disease proved intractable, and he continued subject to attacks of growing intensity at frequent intervals till the close of his life. In 1727 his father had died, and on his return home it was necessary for him, as the younger son, to choose a profession. Having chosen the army, he obtained through the interest of his friends a cornet’s commission in the dragoons. But his military career was destined to be short. His elder brother Thomas having been returned at the general election of 1734 both for Oakhampton and for Old Sarum, and having preferred to sit for the former, the family borough fell to the younger brother by the sort of natural right usually recognized in such cases. Accordingly, in February 1735, William Pitt entered parliament as member for Old Sarum. Attaching himself at once to the formidable band of discontented Whigs known as the Patriots, whom Walpole’s love of exclusive power had forced into opposition under Pulteney, he became in a very short time one of its most prominent members. His maiden speech was delivered in April 1736, in the debate on the congratulatory address to the king on the marriage of the prince of Wales. The occasion was one of compliment, and there is nothing striking in the speech as reported; but it served to gain for him the attention of the house when he presented himself, as he soon afterwards did, in debates of a party character. So obnoxious did he become as a critic of the government, that Walpole thought fit to punish him by procuring his dismissal from the army. Some years later he had occasion vigorously to denounce the system of cashiering officers for political differences, but with characteristic loftiness of spirit he disdained to make any reference to his own case. The loss of his commission was soon made up to him. The heir to the throne, as was usually the case in the house of Hanover, if not in reigning families generally, was the patron of the opposition, and the ex-cornet became groom of the bed-chamber to the prince of Wales. In this new position his hostility to the government did not, as may be supposed, in any degree relax. He had all the natural gifts an orator could desire—a commanding presence, a graceful though somewhat theatrical bearing, an eye of piercing brightness, and a voice of the utmost flexibility. His style, if occasionally somewhat turgid, was elevated and passionate, and it always bore the impress of that intensity of conviction which is the most powerful instrument a speaker can have to sway the convictions of an audience. It was natural, therefore, that in the series of stormy debates, protracted through several years, that ended in the downfall of Walpole, his eloquence should have been one of the strongest of the forces that combined to bring about the final result. Specially effective, according to contemporary testimony, were his speeches against the Hanoverian subsidies, against the Spanish convention in 1739, and in favour of the motion in 1742 for an investigation into the last ten years of Walpole’s administration. It must be borne in mind that the reports of these speeches which have come down to us were made from hearsay, or at best from recollection, and are necessarily therefore most imperfect. The best-known specimen of Pitt’s eloquence, his reply to the sneers of Horatio Walpole at his youth and declamatory manner, which has found a place in so many handbooks of elocution, is evidently, in form at least, the work, not of Pitt, but of Dr Johnson, who furnished the report to the Gentleman’s Magazine. Probably Pitt did say something of the kind attributed to him, though even this is by no means certain in view of Johnson’s repentant admission that he had often invented not merely the form, but the substance of entire debates.

In 1742 Walpole was at last forced to succumb to the long-continued attacks of opposition, and was succeeded as prime minister by the earl of Wilmington, though the real power in the new government was divided between Carteret and the Pelhams. Pitt’s conduct on the change of administration was open to grave censure. The relentless vindictiveness with which he insisted on the prosecution of Walpole, and supported the bill of indemnity to witnesses against the fallen minister, was in itself not magnanimous; but it appears positively unworthy when it is known that a short time before Pitt had offered, on certain conditions, to use all his influence in the other direction. Possibly he was embittered at the time by the fact that, owing to the strong personal dislike of the king, caused chiefly by the contemptuous tone in which he had spoken of Hanover, he did not by obtaining a place in the new ministry reap the fruits of the victory to which he had so largely contributed. The so-called “broad-bottom” administration formed by the Pelhams in 1744, after the dismissal of Carteret, though it included several of those with whom he had been accustomed to act, did not at first include Pitt himself even in a subordinate office. Before the obstacle to his admission was overcome, he had received a remarkable accession to his private fortune. The eccentric duchess of Marlborough, dying in 1744, at the age of ninety, left him a legacy of £10,000 as an “acknowledgment of the noble defence he had made for the support of the laws of England and to prevent the ruin of his country.” As her hatred was known to be at least as strong as her love, the legacy was probably as much a mark of her detestation of Walpole as of her admiration of Pitt. It may be mentioned here, though it does not come in chronological order, that Pitt was a second time the object of a form of acknowledgment of public virtue which few statesmen have had the fortune to receive even once. About twenty years after the Marlborough legacy, Sir William Pynsent, a Somersetshire baronet to whom he was personally quite unknown, left him his entire estate, worth about three thousand a year, in testimony of approval of his political career.

It was with no very good grace that the king at length consented to give Pitt a place in the government, although the latter did all he could to ingratiate himself at court, by changing his tone on the questions on which he had made himself offensive. To force the matter, the Pelhams had to resign expressly on the question whether he should be admitted or not, and it was only after all other arrangements had proved impracticable, that they were reinstated with the obnoxious politician as vice-treasurer of Ireland. This was in February 1746. In May of the same year he was promoted to the more important and lucrative office of paymaster-general, which gave him a place in the privy council, though not in the cabinet. Here he had an opportunity of displaying his public spirit and integrity in a way that deeply impressed both the king and the country. It had been the usual practice of previous paymasters to appropriate to themselves the interest of all money lying in their hands by way of advance, and also to accept a commission of ½% on all foreign subsidies. Although there was no strong public sentiment against the practice, Pitt altogether refused to profit by it. All advances were lodged by him in the Bank of England until required, and all subsidies were paid over without deduction, even though it was pressed upon him, so that he did not draw a shilling from his office beyond the salary legally attaching to it. Conduct like this, though obviously disinterested, did not go without immediate and ample reward, in the public confidence which it created, and which formed the mainspring of Pitt’s power as a statesman.

The administration formed in 1746 lasted without material change till 1754. It would appear from his published correspondence that Pitt had a greater influence in shaping its policy than his comparatively subordinate position would in itself have entitled him to. His conduct in supporting measures, such as the Spanish treaty and the continental subsidies, which he had violently denounced when in opposition, had been much criticized; but within certain limits, not indeed very well defined, inconsistency has never been counted a vice in an English statesman. The times change, and he is not blamed for changing with the times. Pitt in office, looking back on the commencement of his public life, might have used the plea “A good deal has happened since then,” at least as justly as some others have done. Allowance must always be made for the restraints and responsibilities of office. In Pitt’s case, too, it is to be borne in mind that the opposition with which he had acted gradually dwindled away, and that it ceased to have any organized existence after the death of the prince of Wales in 1751. Then in regard to the important question with Spain as to the right of search, 3 Pitt has disarmed criticism by acknowledging that the course he followed during Wapole’s administration was indefensible. All due weight being given to these various considerations, it must be admitted, nevertheless, that Pitt did overstep the limits within which inconsistency is usually regarded as venial. His one great object was first to gain office, and then to make his tenure of office secure by conciliating the favour of the king. The entire revolution which much of his policy underwent in order to effect this object bears too close a resemblance to the sudden and inexplicable changes of front habitual to placemen of the Tadpole stamp to be altogether pleasant to contemplate in a politician of pure aims and lofty ambition. Humiliating is not too strong a term to apply to a letter in which he expresses his desire to “efface the past by every action of his life,” in order that he may stand well with the king.

In 1754 Henry Pelham died, and was succeeded at the head of affairs by his brother, the duke of Newcastle. To Pitt the change brought no advancement, and he had thus an opportunity of testing the truth of the description of his chief given by Sir Robert Walpole, “His name is treason.” But there was for a time no open breach. Pitt continued at his post; and at the general election which took place during the year he even accepted a nomination for the duke’s pocket borough of Aldborough. He had sat for Seaford since 1747. When parliament met, however, he was not long in showing the state of his feelings. Ignoring Sir Thomas Robinson, the political nobody to whom Newcastle had entrusted the management of the Commons, he made frequent and vehement attacks on Newcastle himself, though still continuing to serve under him. In this strange state matters continued for about a year. At length, just after the meeting of parliament in November 1751, Pitt was dismissed from office, having on the debate on the address spoken at great length against a new system of continental subsidies, proposed by the government of which he was a member. Fox, who had just before been appointed secretary of state, retained his place, and though the two men continued to be of the same party, and afterwards served again in the same government, there was henceforward a rivalry between them, which makes the celebrated opposition of their illustrious sons seem like an inherited quarrel.

Another year had scarcely passed when Pitt was again in power. The inherent weakness of the government, the vigour and eloquence of his opposition, and a series of military disasters abroad combined to rouse a public feeling of indignation which could not be withstood, and in December 1756 Pitt, who now sat for Okehampton, became secretary of state, and leader of the Commons under the premiership of the duke of Devonshire. He had made it a condition of his joining any administration that Newcastle should be excluded from it, thus showing a resentment which, though natural enough, proved fatal to the lengthened existence of his government. With the king unfriendly, and Newcastle, whose corrupt influence was still dominant in the Commons, estranged, it was impossible to carry on a government by the aid of public opinion alone, however emphatically that might have declared itself on his side. In April 1757, accordingly, he found himself again dismissed from office on account of his opposition to the king’s favourite continental policy. But the power that was insufficient to keep him in office was strong enough to make any arrangement that excluded him impracticable. The public voice spoke in a way that was not to be mistaken. Probably no English minister ever received in so short a time so many proofs of the confidence and admiration of the public, the capital and all the chief towns voting him addresses and the freedom of their corporations. From the political deadlock that ensued relief could only be had by an arrangement between Newcastle and Pitt. After some weeks’ negotiation, in the course of which the firmness and moderation of “the Great Commoner,” as he had come to be called, contrasted favourably with the characteristic tortuosities of the crafty peer, matters were settled on such a basis that, while Newcastle was the nominal, Pitt was the virtual head of the government. On his acceptance of office he was chosen member for Bath.

This celebrated administration was formed in June 1757, and continued in power till 1761. During the four years of its existence it has been usual to say that the biography of Pitt is the history of England, so thoroughly was he identified with the great events which make this period, in so far as the external relations of the country are concerned, one of the most glorious in her annals. A detailed account of these events belongs to history; all that is needed in a biography is to point out the extent to which Pitt’s personal influence may really be traced in them. It is scarcely too much to say that, in the general opinion of his contemporaries, the whole glory of these years was due to his single genius; his alone was the mind that planned, and his the spirit that animated the brilliant achievements of the British arms in all the four quarters of the globe. Posterity, indeed, has been able to recognize more fully the independent genius of those who carried out his purposes. The heroism of Wolfe would have been irrepressible, Clive would have proved himself “a heaven-born general,” and Frederick the Great would have written his name in history as one of the most skilful strategists the world has known, whoever had held the seals of office in England. But Pitt’s relation to all three was such as to entitle him to a large share in the credit of their deeds. It was his discernment that selected Wolfe to lead the attack on Quebec, and gave him the opportunity of dying a victor on the heights of Abraham. He had personally less to do with the successes in India than with the other great enterprises that shed an undying lustre on his administration; but his generous praise in parliament stimulated the genius of Clive, and the forces that acted at the close of the struggle were animated by his indomitable spirit. Pitt, the first real Imperialist in modern English history, was the directing mind in the expansion of his country, and with him the beginning of empire is rightly associated. The Seven Years’ War might well, moreover, have been another Thirty Years’ War if Pitt had not furnished Frederick with an annual subsidy of £700,000, and in addition relieved him of the task of defending western Germany against France.

Contemporary opinion was, of course, incompetent to estimate the permanent results gained for the country by the brilliant foreign policy of Pitt. It has long been generally agreed that by several of his most costly expeditions nothing was really won but glory. It has even been said that the only permanent acquisition that England owed directly to him was her Canadian dominion; and, strictly speaking, this is true, it being admitted that the campaign by which the Indian empire was virtually won was not planned by him, though brought to a successful issue during his ministry. But material aggrandizement, though the only tangible, is not the only real or lasting effect of a war policy. More may be gained by crushing a formidable rival than by conquering a province. The loss of her Canadian possessions was only one of a series of disasters suffered by France, which radically affected the future of Europe and the world. Deprived of her most valuable colonies both in the East and in the West, and thoroughly defeated on the continent, her humiliation was the beginning of a new epoch in history. The victorious policy of Pitt destroyed the military prestige which repeated experience has shown to be in France as in no other country the very life of monarchy, and thus was not the least considerable of the many influences that slowly brought about the French Revolution. It effectually deprived her of the lead in the councils of Europe which she had hitherto arrogated to herself, and so affected the whole course of continental politics. It is such far-reaching results as these, and not the mere acquisition of a single colony, however valuable, that constitute Pitt’s claim to be considered as on the whole the most powerful minister that ever guided the foreign policy of England.

The first and most important of a series of changes which ultimately led to the dissolution of the ministry was the death of George II. on the 25th of October 1760, and the accession of his grandson, George III. The new king had, as was natural, new counsellors of his own, the chief of whom, Lord Bute, was at once admitted to the cabinet as a secretary of state. Between Bute and Pitt there speedily arose an occasion of serious difference. 4 The existence of the so-called family compact by which the Bourbons of France and Spain bound themselves in an offensive alliance against England having been brought to light, Pitt urged that it should be met by an immediate declaration of war with Spain. To this course Bute would not consent, and as his refusal was endorsed by all his colleagues save Temple, Pitt had no choice but to leave a cabinet in which his advice on a vital question had been rejected. On his resignation, which took place in October 1761, the king urged him to accept some signal mark of royal favour in the form most agreeable to himself. Accordingly he obtained a pension of £3000 a year for three lives, and his wife, Lady Hester Grenville, whom he had married in 1754, was created Baroness Chatham in her own right. In connexion with the latter gracefully bestowed honour it may be mentioned that Pitt’s domestic life was a singularly happy one.

Pitt’s spirit was too lofty to admit of his entering on any merely factious opposition to the government he had quitted. On the contrary, his conduct after his retirement was distinguished by a moderation and disinterestedness which, as Burke has remarked, “set a seal upon his character.” The war with Spain, in which he had urged the cabinet to take the initiative, proved inevitable; but he scorned to use the occasion for “altercation and recrimination,” and spoke in support of the government measures for carrying on the war. To the preliminaries of the peace concluded in February 1763 he offered an indignant resistance, considering the terms quite inadequate to the successes that had been gained by the country. When the treaty was discussed in parliament in December of the preceding year, though suffering from a severe attack of gout, he was carried down to the House, and in a speech of three hours’ duration, interrupted more than once by paroxysms of pain, he strongly protested against its various conditions. The physical cause which rendered this effort so painful probably accounts for the infrequency of his appearances in parliament, as well as for much that is otherwise inexplicable in his subsequent conduct. In 1763 he spoke against the obnoxious tax on cider, imposed by his brother-in-law, George Grenville, and his opposition, though unsuccessful in the House, helped to keep alive his popularity with the country, which cordially hated the excise and all connected with it. When next year the question of general warrants was raised in connexion with the case of Wilkes, Pitt vigorously maintained their illegality, thus defending at once the privileges of Parliament and the freedom of the press. During 1765 he seems to have been totally incapacitated for public business. In the following year he supported with great power the proposal of the Rockingham administration for the repeal of the American Stamp Act, arguing that it was unconstitutional to impose taxes upon the colonies. He thus endorsed the contention of the colonists on the ground of principle, while the majority of those who acted with him contented themselves with resisting the disastrous taxation scheme on the ground of expediency. The Repeal Act, indeed, was only passed pari passu with another censuring the American assemblies, and declaring the authority of the British parliament over the colonies “in all cases whatsoever”; so that the House of Commons repudiated in the most formal manner the principle Pitt laid down. His language in approval of the resistance of the colonists was unusually bold, and perhaps no one but himself could have employed it with impunity at a time when the freedom of debate was only imperfectly conceded.

Pitt had not been long out of office when he was solicited to return to it, and the solicitations were more than once renewed. Unsuccessful overtures were made to him in 1763, and twice in 1765, in May and June—the negotiator in May being the king’s uncle, the duke of Cumberland, who went down in person to Hayes, Pitt’s seat in Kent. It is known that he had the opportunity of joining the marquis of Rockingham’s short-lived administration at any time on his own terms, and his conduct in declining an arrangement with that minister has been more generally condemned than any other step in his public life. In July 1766 Rockingham was dismissed, and Pitt was entrusted by the king with the task of forming a government entirely on his own conditions. The result was a cabinet, strong much beyond the average in its individual members, but weak to powerlessness in the diversity of its composition. Burke, in a memorable passage of a memorable speech, has described this “chequered and speckled” administration with great humour, speaking of it as “indeed a very curious show, but utterly unsafe to touch and unsure to stand on.” Pitt chose for himself the office of lord privy seal, which necessitated his removal to the House of Lords; and in August he became earl of Chatham and Viscount Pitt.

By the acceptance of a peerage the great commoner lost at least as much and as suddenly in popularity as he gained in dignity. One significant indication of this may be mentioned. In view of his probable accession to power, preparations were made in the city of London for a banquet and a general illumination to celebrate the event. But the celebration was at once countermanded when it was known that he had become earl of Chatham. The instantaneous revulsion of public feeling was somewhat unreasonable, for Pitt’s health seems now to have been beyond doubt so shattered by his hereditary malady, that he was already in old age though only fifty-eight. It was natural, therefore, that he should choose a sinecure office, and the ease of the Lords. But a popular idol nearly always suffers by removal from immediate contact with the popular sympathy, be the motives for removal what they may.

One of the earliest acts of the new ministry was to lay an embargo upon corn, which was thought necessary in order to prevent a dearth resulting from the unprecedentedly bad harvest of 1766. The measure was strongly opposed, and Lord Chatham delivered his first speech in the House of Lords in support of it. It proved to be almost the only measure introduced by his government in which he personally interested himself. His attention had been directed to the growing importance of the affairs of India, and there is evidence in his correspondence that he was meditating a comprehensive scheme for transferring much of the power of the company to the crown, when he was withdrawn from public business in a manner that has always been regarded as somewhat mysterious. It may be questioned, indeed, whether even had his powers been unimpaired he could have carried out any decided policy on any question with a cabinet representing interests so various and conflicting; but, as it happened, he was incapacitated physically and mentally during nearly the Whole period of his tenure of office. He scarcely ever saw any of his colleagues though they repeatedly and urgently pressed for interviews with him, and even an offer from the king to visit him in person was declined, though in the language of profound and almost abject respect which always marked his communications with the court. It has been insinuated both by contemporary and by later critics that being disappointed at his loss of popularity, and convinced of the impossibility of co-operating with his colleagues, he exaggerated his malady as a pretext for the inaction that was forced upon him by circumstances. But there is no sufficient reason to doubt that he was really, as his friends represented, in a state that utterly unfitted him for business. He seems to have been freed for a time from the pangs of gout only to be afflicted with a species of mental alienation bordering on insanity. This is the most satisfactory, as it is the most obvious, explanation of his utter indifference in presence of one of the most momentous problems that ever pressed for solution on an English statesman. Those who are able to read the history in the light of what occurred later may perhaps be convinced that no policy whatever initiated, after 1766 could have prevented or even materially delayed the declaration of American independence; but to the politicians of that time the coming event had not yet cast so dark a shadow before as to paralyse all action, and if any man could have allayed the growing discontent of the colonists and prevented the ultimate dismemberment of the empire, it would have been Lord Chatham. The fact that he not only did nothing to remove existing difficulties, but remained passive while his colleagues took the fatal step which led directly to separation, is in itself clear proof of his entire incapacity. The imposition 5 of the import duty on tea and other commodities was the project of Charles Townshend, and was carried into effect in 1767 without consultation with Lord Chatham, if not in opposition to his wishes. It is probably the most singular thing in connexion with this singular administration, that its most pregnant measure should thus have been one directly opposed to the well-known principles of its head.

For many months things remained in the curious position that he who was understood to be the head of the cabinet had as little share in the government of the country as an unenfranchised peasant. As the chief could not or would not lead, the subordinates naturally chose their own paths and not his. The lines of Chatham’s policy were abandoned in other cases besides the imposition of the import duty; his opponents were taken into confidence; and friends, such’ as Amherst and Shelburne, were dismissed from their posts. When at length in October 1768 he tendered his resignation on the ground of shattered health, he did not fail to mention the dismissal of Amherst and Shelburne as a personal grievance.

Soon after his resignation a renewed attack of gout freed Chatham from the mental disease under which he had so long suffered. He had been nearly two years and a half in seclusion when, in July 1769, he again appeared in public at a royal levee. It was not, however, until 1770 that he resumed his seat in the House of Lords. He had now almost no personal following, mainly owing to the grave mistake he had made in not forming an alliance with the Rockingham party. But his eloquence was as powerful as ever, and all its power was directed against the government policy in the contest with America, which had become the question of all-absorbing interest. His last appearance in the House of Lords was on the 7th of April 1778, on the occasion of the duke of Richmond’s motion for an address praying the king to conclude peace with America on any terms. In view of the hostile demonstrations of France the various parties had come generally to see the necessity of such a measure. But Chatham could not brook the thought of a step which implied submission to the “natural enemy” whom it had been the main object of his life to humble, and he declaimed for a considerable time, though with sadly diminished vigour, against the motion. After the duke of Richmond had replied, he rose again excitedly as if to speak, pressed his hand upon his breast, and fell down in a fit. He was removed to his seat at Hayes, where he died on the 11th of May. With graceful unanimity all parties combined to show their sense of the national loss. The Commons presented an address to the king praying that the deceased statesman might be buried with the honours of a public funeral, and voted a sum for a public monument which was erected over his grave in Westminster Abbey. Soon after the funeral a bill was passed bestowing a pension of £4000 a year on his successors in the earldom. He had a family of three sons and two daughters, of whom the second son, William, was destined to add fresh lustre to a name which is one of the greatest in the history of England.

Dr Johnson is reported to have said that “Walpole was a minister given by the king to the people, but Pitt was a minister given by the people to the king,” and the remark correctly indicates Chatham’s distinctive place among English statesmen. He was the first minister whose main strength lay in the support of the nation at large as distinct from its representatives in the Commons, where his personal following was always small. He was the first to discern that public opinion, though generally slow to form and slow to act, is in the end the paramount power in the state; and he was the first to use it not in an emergency merely, but throughout a whole political career. He marks the commencement of that vast change in the movement of English politics by which it has come about that the sentiment of the great mass of the people now tells effectively on the action of the government from day to day,—almost from hour to hour. He was well fitted to secure the sympathy and admiration of his countrymen, for his virtues and his failings were alike English. He was often inconsistent, he was generally intractable and overbearing, and he was always pompous and affected to a degree which, Macaulay has remarked, seems scarcely compatible with true greatness. Of the last quality evidence is furnished in the stilted style of his letters, and in the fact recorded by Seward that he never permitted his under-secretaries to sit in his presence. Burke speaks of “some significant, pompous, creeping, explanatory, ambiguous matter, in the true Chathamic style.” But these defects were known only to the inner circle of his associates. To the outside public he was endeared as a statesman who could do or suffer “nothing base,” and who had the rare power of transfusing his own indomitable energy and courage into all who served under him. “A spirited foreign policy” has always been popular in England, and Pitt was the most popular of English ministers, because he was the most successful exponent of such a policy. In domestic affairs his influence was small and almost entirely indirect. He himself confessed his unfitness for dealing with questions of finance. The commercial prosperity that was produced by his war policy was in a great part delusive, as prosperity so produced must always be, though it had permanent effects of the highest moment in the rise of such centres of industry as Glasgow. This, however, was a remote result which he could have neither intended nor foreseen.

CHATHAM, also called Miramichi, an incorporated town and port of entry in Northumberland county, New Brunswick, Canada, on the Miramichi river, 24 m. from its mouth and 10 m. by rail from Chatham junction on the Intercolonial railway. Pop. (1901) 5000. The town contains the Roman Catholic pro-cathedral, many large saw-mills, pulp-mills, and several establishments for curing and exporting fish. The lumber trade, the fisheries, and the manufacture of pulp are the chief industries.

CHATHAM, a city and port of entry of Ontario, Canada, and the capital of Kent county, situated 64 m. S.W. of London, and 11 m. N. of Lake Erie, on the Thames river and the Grand Trunk, Canadian Pacific and Lake Erie & Detroit River railways. Pop. (1901) 9068. It has steamboat connexion with Detroit and the cities on Lakes Huron and Erie. It is situated in a rich agricultural and fruit-growing district, and carries on a large export trade. It contains a large wagon factory, planing and flour mills, manufactories of fanning mills, binder-twine, woven wire goods, engines, windmills, &c.

CHATHAM, a port and municipal and parliamentary borough of Kent, England, on the right bank of the Medway, 34 m. E.S.E. of London by the South-Eastern & Chatham railway. Pop. (1891) 31,657; (1901) 37,057. Though a distinct borough it is united on the west with Rochester and on the east with Gillingham, so that the three boroughs form, in appearance, a single town with a population which in 1901 exceeded 110,000. With the exception of the dockyards and fortifications there are few objects of interest. St Mary’s church was opened in 1903, but occupies a site which bore a church in Saxon times, though the previous building dated only from 1786. A brass commemorates Stephen Borough (d. 1584), discoverer of the northern passage to Archangel in Russia (1553). St Bartholomew’s chapel, originally attached to the hospital for lepers (one of the first in England), founded by Gundulph, bishop of Rochester, in 1070, is in part Norman. The funds for the maintenance of the hospital were appropriated by decision of the court of chancery to the hospital of St Bartholomew erected in 1863 within the boundaries of Rochester. The almshouse established in 1592 by Sir John Hawkins for decayed seamen and shipwrights is still extant, the building having been re-erected in the 19th century; but the fund called the Chatham Chest, originated by Hawkins and Drake in 6 1588, was incorporated with Greenwich Hospital in 1802. In front of the Royal Engineers’ Institute is a statue (1890) of General Gordon, and near the railway station another (1888) to Thomas Waghorn, promoter of the overland route to India. In 1905 King Edward VII. unveiled a fine memorial arch commemorating Royal Engineers who fell in the South African War. It stands in the parade ground of the Brompton barracks, facing the Crimean arch. There are numerous brickyards, lime-kilns and flour-mills in the district neighbouring to Chatham; and the town carries on a large retail trade, in great measure owing to the presence of the garrison. The fortifications are among the most elaborate in the kingdom. The so-called Chatham Lines enclose New Brompton, a part of the borough of Gillingham. They were begun in 1758 and completed in 1807, but have been completely modernized. They are strengthened by several detached forts and redoubts. Fort Pitt, which rises above the town to the west, was built in 1779, and is used as a general military hospital. It was regarded as the principal establishment of the kind in the country till the foundation of Netley in Hampshire. The lines include the Chatham, the Royal Marine, the Brompton, the Hut, St Mary’s and naval barracks; the garrison hospital, Melville hospital for sailors and marines, the arsenal, gymnasium, various military schools, convict prison, and finally the extensive dockyard system for which the town is famous. This dockyard covers an area of 516 acres, and has a river frontage of over 3 m. It was brought into its present state by the extensive works begun about 1867. Before that time there was no basin or wet-dock, though the river Medway to some extent answered the same purpose, but a portion of the adjoining salt-marshes was then taken in, and three basins have been constructed, communicating with each other by means of large locks, so that ships can pass from the bend of the Medway at Gillingham to that at Upnor. Four graving docks were also formed, opening out of the first (Upnor) basin. Subsequent improvements included dredging operations in the Medway to improve the approach, and the provision of extra dry-dock accommodation under the Naval Works Acts.

The parliamentary borough returns one member. The town was incorporated in 1890, and is governed by a mayor, six aldermen and eighteen councillors. Area, 4355 acres. The borough includes the suburb (an ecclesiastical parish) of Luton, in which are the waterworks of Chatham and the adjoining towns.

Chatham (Ceteham, Chetham) belonged at the time of the Domesday Survey to Odo, bishop of Bayeux. During the middle ages it formed a suburb of Rochester, but Henry VIII. in founding a regular navy began to establish dockyards, and the harbour formed by the deep channel of the Medway was utilized by Elizabeth, who built a dockyard and established an arsenal here. The dockyard was altered and improved by Charles I. and Charles II., and became the chief naval station of England. In 1708 an act was passed for extending the fortifications of Chatham. During the excavations on Chatham Hill after 1758 a number of tumuli containing human remains, pottery, coins, &c., suggestive of an ancient settlement, were found. Chatham was constituted a parliamentary borough by the Reform Bill of 1832. In the time of Edward III. the lord of the manor had two fairs, one on the 24th of August and the other on the 8th of September. A market to be held on Tuesday, and a fair on the 4th, 5th and 6th of May, were granted by Charles II. in 1679, and another provision market on Saturday by James II. in 1688. In 1738 fairs were held on the 4th of May and the 8th of September, and a market every Saturday.

CHATHAM ISLANDS, a small group in the Pacific Ocean, forming part of New Zealand, 536 m. due E. of Lyttelton in the South Island, about 44° S., 177° W. It consists of three islands, a large one called Whairikauri, or Chatham Island, a smaller one, Rangihaute, or Pitt Island, and a third, Rangatira, or South-east Island. There are also several small rocky islets. Whairikauri, whose highest point reaches about 1000 ft., is remarkable for the number of lakes and tarns it contains, and for the extensive bogs which cover the surface of nearly the whole of the uplands. It is of very irregular form, about 38 m. in length and 25 m. in extreme breadth, with an area of 321 sq. m.—a little larger than Middlesex. The geological formation is principally of volcanic rocks, with schists and tertiary limestone; and an early physical connexion of the islands with New Zealand is indicated by their geology and biology. The climate is colder than that of New Zealand. In the centre of Whairikauri is a large brackish lake called Tewanga, which at the southern end is separated from the sea by a sandbank only 150 yds. wide, which it occasionally bursts through. The southern part of the island has an undulating surface, and is covered either with an open forest or with high ferns. In general the soil is extremely fertile, and where it is naturally drained a rich vegetation of fern and flax occurs. On the north-west are several conical hills of basalt, which are surrounded by oases of fertile soil. On the south-western side is Petre Bay, on which, at the mouth of the river Mantagu, is Waitangi, the principal settlement.

The islands were discovered in 1791 by Lieutenant W.R. Broughton (1762-1821), who gave them the name of Chatham from the brig which he commanded. He described the natives as a bright, pleasure-loving people, dressed in sealskins or mats, and calling themselves Morioris or Maiorioris. In 1831 they were conquered by 800 Maoris who were landed from a European vessel. They were almost exterminated, and an epidemic of influenza in 1839 killed half of those left; ten years later there were only 90 survivors out of a total population of 1200. They subsequently decreased still further. Their language was allied to that of the Maoris of New Zealand, but they differed somewhat from them in physique, and they were probably a cross between an immigrating Polynesian group and a lower indigenous Melanesian stock. The population of the islands includes about 200 whites of various races and the same number of natives (chiefly Maoris). Cattle and sheep are bred, and a trade is carried on in them with the whalers which visit these seas. The chief export from the group is wool, grown upon runs farmed both by Europeans and Morioris. There is also a small export by the natives of the flesh of young albatrosses and other sea-birds, boiled down and cured, for the Maoris of New Zealand, by whom it is reckoned a delicacy. The imports consist of the usual commodities required by a population where little of the land is actually cultivated.

There are no indigenous mammals; the reptiles belong to New Zealand species. The birds—the largest factor in the fauna—have become very greatly reduced through the introduction of cats, dogs and pigs, as well as by the constant persecution of every sort of animal by the natives. The larger bell-bird (Anthornis melanocephala) has become quite scarce; the magnificent fruit-pigeon (Carpophaga chathamensis), and the two endemic rails (Nesolimnas dieffenbachii and Cabalus modestus), the one of which was confined to Whairikauri and the other to Mangare Island, are extinct. Several fossil or subfossil avian forms, very interesting from the point of view of geographical distribution, have been discovered by Dr H.O. Forbes, namely, a true species of raven (Palaeocorax moriorum), a remarkable rail (Diaphorapteryx), closely related to the extinct Aphanapteryx of Mauritius, and a large coot (Palaeolimnas chathamensis). There have also been discovered the remains of a species of swan belonging to the South American genus Chenopis, and of the tuatara (Hatteria) lizard, the unique species of an ancient family now surviving only in New Zealand. The swan is identical with an extinct species found in caves and kitchen-middens in New Zealand, which was contemporaneous with the prehistoric Maoris and was largely used by them for food. One of the finest of the endemic flowering plants of the group is the boraginaceous “Chatham Island lily” (Myositidium nobile), a gigantic forget-me-not, which grows on the shingly shore in a few places only, and always just on the high-water mark, where it is daily deluged by the waves; while dracophyllums, leucopogons and arborescent ragworts are characteristic forms in the vegetation.

CHÂTILLON, the name of a French family whose history has furnished material for a large volume in folio by A. du Chesne, a learned Frenchman, published in 1621. But in spite of its merits this book presents a certain number of inaccurate statements, some of which it is important to notice. If, for instance, it be true that the Châtillons came from Châtillon-sur-Marne (Marne, arrondissement of Reims), it is now certain that, since the 11th century, this castle belonged to the count of Champagne, and that the head of the house of Châtillon was merely tenant in that place. One of them, however, Gaucher of Châtillon, lord of Crécy and afterwards constable of France, became in 1290 lord of Châtillon-sur-Marne by exchange, but since 1303 a new agreement allotted to him the countship of Porcien, while Châtillon reverted to the domain of the counts of Champagne. It may be well to mention also that, in consequence of a resemblance of their armorial bearings, du Chesne considered wrongly that the lords of Bazoches and those of Château-Porcien of the 12th and 13th centuries drew their descent from the house of Châtillon.

The most important branches of the house of Châtillon were those of (1) St Pol, beginning with Gaucher III. of Châtillon, who became count of St Pol in right of his wife Isabella in 1205, the last male of the line being Guy V. (d. 1360); (2) Blois, founded by the marriage of Hugh of Châtillon-St Pol (d. 1248) with Mary, daughter of Margaret of Blois (d. 1230),—this branch became extinct with the death of Guy II. in 1397; (3) Porcien, from 1303 to 1400, when Count John sold the countship to Louis, duke of Orleans; (4) Penthièvre, by the marriage of Charles of Blois (d. 1364) with Jeanne (d. 1384), heiress of Guy, count of Penthièvre (d. 1331), the male line becoming extinct in 1457.

CHÂTILLON-SUR-SEINE, a town of eastern France, capital of an arrondissement in the department of Côte-d’Or, on the Eastern and Paris-Lyon railways, 67 m. N.N.W. of Dijon, between that city and Troyes. Pop. (1906) 4430. It is situated on both banks of the upper Seine, which is swelled at its entrance to the town by the Douix, one of the most abundant springs in France. Châtillon is constructed on ample lines and rendered attractive by beautiful promenades. Some ruins on an eminence above it mark the site of a château of the dukes of Burgundy. Near by stands the church of St Vorle of the l0th century, but with many additions of later date; it contains a sculptured Holy Sepulchre of the 16th century and a number of frescoes. In a fine park stands a modern château built by Marshal Marmont, duke of Ragusa, born at Châtillon in 1774. It was burnt in 1871, and subsequently rebuilt. The town preserves several interesting old houses. Châtillon has a sub-prefecture, tribunals of first instance and of commerce, a school of agriculture and a communal college. Among its industries are brewing, iron-founding and the manufacture of mineral and other blacks. It has trade in wood, charcoal, lithographic and other stone. Châtillon anciently consisted of two parts, Chaumont, belonging to the duchy of Burgundy, and Bourg, ruled by the bishop of Langres; it did not coalesce into one town till the end of the 16th century. It was taken by the English in 1360 and by Louis XI. in 1475, during his struggle with Charles the Bold. Châtillon was one of the first cities to adhere to the League, but suffered severely from the oppression of its garrisons and governors, and in 1595 made voluntary submission to Henry IV. In modern times it is associated with the abortive conference of 1814 between the representatives of Napoleon and the Allies.

CHATSWORTH, a village of Derbyshire, England, containing a seat belonging to the duke of Devonshire, one of the most splendid private residences in England. Chatsworth House is situated close to the left bank of the river Derwent, 2¾ m. from Bakewell. It is Ionic in style, built foursquare, and enclosing a large open courtyard, with a fountain in the centre. In front, a beautiful stretch of lawn slopes gradually down to the riverside, and a bridge, from which may best be seen the grand façade of the building, as it stands out in relief against the wooded ridge of Bunker’s Hill. The celebrated gardens are adorned with sculptures by Gabriel Gibber; Sir Joseph Paxton designed the great conservatory, unrivalled in Europe, which covers an acre; and the fountains, which include one with a jet 260 ft. high, are said to be surpassed only by those at Versailles. Within the house there is a very fine collection of pictures, including the well-known portraits by Reynolds of Georgiana, duchess of Devonshire. Other paintings are ascribed to Holbein, Dürer, Murillo, Jan van Eyck, Dolci, Veronese and Titian. Hung in the gallery of sketches there are some priceless drawings attributed to Michelangelo, Leonardo da Vinci, Raffaelle, Correggio, Titian and other old masters. Statues by Canova, Thorwaldsen, Chantrey and R.J. Wyatt are included among the sculptures. In the state apartments the walls and window-panes are in some cases inlaid with marble or porphyry; the woodcarving, marvellous for its intricacy, grace and lightness of effect, is largely the work of Samuel Watson of Heanor (d. 1715). Chatsworth Park is upwards of 11 m. in circuit, and contains many noble forest-trees, the whole being watered by the Derwent, and surrounded by high moors and uplands. Beyond the river, and immediately opposite the house, stands the model village of Edensor, where most of the cottages were built in villa style, with gardens, by order of the 6th duke. The parish church, restored by the same benefactor, contains an old brass in memory of John Beaton, confidential servant to Mary, queen of Scots, who died in 1570; and in the churchyard are the graves of Lord Frederick Cavendish, murdered in 1882 in Phoenix Park, Dublin, and of Sir Joseph Paxton.

Chatsworth (Chetsvorde, Chetelsvorde, “the court of Chetel”) took its name from Chetel, one of its Saxon owners, who held it of Edward the Confessor. It belonged to the crown and was entrusted by the Conqueror to the custody of William Peverell. Chatsworth afterwards belonged for many generations to the family of Leech, and was purchased in the reign of Elizabeth by Sir William Cavendish, husband of the famous Bess of Hardwick. In 1557 he began to build Chatsworth House, and it was completed after his death by his widow, then countess of Shrewsbury. Here Mary, queen of Scots, spent several years of her imprisonment under the care of the earl of Shrewsbury. During the Civil War, Chatsworth was occasionally occupied as a fortress by both parties. It was pulled down, and the present house begun by William, 1st duke of Devonshire in 1688. The little village consists almost exclusively of families employed upon the estate.

CHATTANOOGA, a city and the county-seat of Hamilton county, Tennessee, U.S.A., in the S.E. part of the state, about 300 m. S. of Cincinnati, Ohio, and 150 m. S.E. of Nashville, Tennessee, on the Tennessee river, and near the boundary line between Tennessee and Georgia. Pop. (1860) 2545; (1870) 6093; (1880) 12,892; (1890) 29,100; (1900) 30,154, of whom 994 were foreign-born and 13,122 were negroes; (U.S. census, 1910) 44,604. The city is served by the Alabama Great Southern (Queen and Crescent), the Cincinnati Southern (leased by the Cincinnati, New Orleans & Texas Pacific railway company), the Nashville, Chattanooga & St Louis (controlled by the Louisville & Nashville), and its leased line, the Western & Atlantic (connecting with Atlanta, Ga.), the Central of Georgia, and the Chattanooga Southern railways, and by freight and passenger steamboat lines on the Tennessee river, which is navigable to and beyond this point during eight months of the year. That branch of the Southern railway extending from Chattanooga to Memphis was formerly the Memphis & Charleston, under which name it became famous in the American Civil War. Chattanooga occupies a picturesque site at a sharp bend of the river. To the south lies Lookout Mountain, whose summit (2126 ft. above the sea; 1495 ft. above the river) commands a magnificent view. To the east rises Missionary Ridge. Fine driveways and electric lines connect with both Lookout Mountain (the summit of which is reached by an inclined plane on which cars are operated by 8 cable) and Missionary Ridge, where there are Federal reservations, as well as with the National Military Park (15 sq. m.; dedicated 1895) on the battlefield of Chickamauga (q.v.); this park was one of the principal mobilization camps of the United States army during the Spanish-American War of 1898. Among the principal buildings are the city hall, the Federal building, the county court house, the public library, the high school and the St Vincent’s and the Baroness Erlanger hospitals. Among Chattanooga’s educational institutions are two commercial colleges, the Chattanooga College for Young Ladies (non-sectarian), the Chattanooga Normal University, and the University of Chattanooga, until June 1907, United States Grant University (whose preparatory department, “The Athens School,” is at Athens, Tenn.), a co-educational institution under Methodist Episcopal control, established in 1867; it has a school of law (1899), a medical school (1889), and a school of theology (1888). East of the city is a large national cemetery containing more than 13,000 graves of Federal soldiers. Chattanooga is an important produce, lumber, coal and iron market, and is the principal trade and jobbing centre for a large district in Eastern Tennessee and Northern Georgia and Alabama. The proximity of coalfields and iron mines has made Chattanooga an iron manufacturing place of importance, its plants including car shops, blast furnaces, foundries, agricultural implement and machinery works, and stove factories; the city has had an important part in the development of the iron and steel industries in this part of the South. There are also flour mills, tanneries (United States Leather Co.), patent medicine, furniture, coffin, woodenware and wagon factories, knitting and spinning mills, planing mills, and sash, door and blind factories—the lumber being obtained from logs floated down the river and by rail. The value of the city’s factory products increased from $10,517,886 in 1900 to $15,193,909 in 1905 or 44.5%.

Chattanooga was first settled about 1835, and was long known as Ross’s Landing. It was incorporated in 1851 as Chattanooga, and received a city charter in 1866. Its growth for the three decades after the Civil War was very rapid. During the American Civil War it was one of the most important strategic points in the Confederacy, and in its immediate vicinity were fought two great battles. During June 1862 it was threatened by a Federal force under General O.M. Mitchel, but the Confederate army of General Braxton Bragg was transferred thither by rail from Corinth, Miss., before Mitchel was able to advance. In September 1863, however, General W.S. Rosecrans, with the Union Army of the Cumberland out-manœuvred Bragg, concentrated his numerous columns in the Chickamauga Valley, and occupied the town, to which, after the defeat of Chickamauga (q.v.), he retired.

From the end of September to the 24th of November the Army of the Cumberland was then invested in Chattanooga by the Confederates, whose position lay along Missionary Ridge from its north end near the river towards Rossville, whence their entrenchments extended westwards to Lookout Mountain, which dominates the whole ground, the Tennessee running directly beneath it. Thus Rosecrans was confined to a semicircle of low ground around Chattanooga itself, and his supplies had to make a long and difficult détour from Bridgeport, the main road being under fire from the Confederate position on Lookout and in the Wauhatchie valley adjacent. Bragg indeed expected that Rosecrans would be starved into retreat. But the Federals once more, and this time on a far larger scale, concentrated in the face of the enemy. The XI. and XII. corps from Virginia under Hooker were transferred by rail to reinforce Rosecrans; other troops were called up from the Mississippi, and on the 16th of October the Federal government reconstituted the western armies under the supreme command of General Grant. The XV. corps of the Army of the Tennessee, under Sherman, was on the march from the Mississippi. Hooker’s troops had already arrived when Grant reached Chattanooga on the 23rd of October. The Army of the Cumberland was now under Thomas, Rosecrans having been recalled. The first action was fought at Brown’s Ferry in the Wauhatchie valley, where Hooker executed with complete precision a plan for the revictualling of Chattanooga, established himself near Wauhatchie on the 28th, and repulsed a determined attack on the same night. But Sherman was still far distant, and the Federal forces at Knoxville, against which a large detachment of Bragg’s army under Longstreet was now sent, were in grave danger. Grant waited for Sherman’s four divisions, but prepared everything for battle in the meantime. His plan was that Thomas in the Chattanooga lines should contain the Confederate centre on Missionary Ridge, while Hooker on the right at Wauhatchie was to attack Lookout Mountain, and Sherman farther up the river was to carry out the decisive attack against Bragg’s extreme right wing at the end of Missionary Ridgg. The last marches of the XV. corps were delayed, by stormy weather, Bragg reinforced Longstreet, and telegraphic communication between Grant and the Federals at Knoxville had already ceased. But Grant would not move forward without Sherman, and the battle of Chattanooga was fought more than two months after Chickamauga. On the 23rd of November a forward move of Thomas’s army, intended as a demonstration, developed into a serious and successful action, whereby the first line of the Confederate centre was driven in for some distance. Bragg was now much weakened by successive detachments having been sent to Knoxville, and on the 24th the real battle began. Sherman’s corps was gradually brought over the river near the mouth of Chickamauga Creek, and formed up on the east side.

The attack began at 1 P.M. and was locally a complete success. The heights attacked were in Sherman’s hands, and fortified against counter-attack, before nightfall. Hooker in the meanwhile had fought the “Battle above the Clouds” on the steep face of Lookout Mountain, and though opposed by an equal force of Confederates, had completely driven the enemy from the mountain. The 24th then had been a day of success for the Federals, and the decisive attack of the three armies in concert was to take place on the 25th. But the maps deceived Grant and Sherman as they had previously deceived Rosecrans. Sherman had captured, not the north point of Missionary Ridge, but a detached hill, and a new and more serious action had to be fought for the possession of Tunnel Hill, where Bragg’s right now lay strongly entrenched. The Confederates used every effort to hold the position and all Sherman’s efforts were made in vain. Hooker, who was moving on Rossville, had not progressed far, and Bragg was still free to reinforce his right. Grant therefore directed Thomas to move forward on the centre to relieve the 9 pressure on Sherman. The Army of the Cumberland was, after all, to strike the decisive blow. About 3.30 P.M. the centre advanced on the Confederate’s trenches at the foot of Missionary Ridge. These were carried at the first rush, and the troops were ordered to lie down and await orders. Then occurred one of the most dramatic episodes of the war. Suddenly, and without orders either from Grant or the officers at the front, the whole line of the Army of the Cumberland rose and rushed up the ridge. Two successive lines of entrenchments were carried at once. In a short time the crest was stormed, and after a last attempt at resistance the enemy’s centre fled in the wildest confusion. The pursuit was pressed home by the divisional generals, notably by Sheridan. Hooker now advanced in earnest on Rossville, and by nightfall the whole Confederate army, except the troops on Tunnel Hill, was retreating in disorder. These too were withdrawn in the night, and the victory of the Federals was complete. Bragg lost 8684 men killed, wounded and prisoners out of perhaps 34,000 men engaged; Grant, with 60,000 men, lost about 6000.

CHATTEL (for derivation see Cattle), a term used in English law as equivalent to “personal property,” that is, property which, on the death of the owner, devolves on his executor or administrator to be distributed (unless disposed of by will) among the next of kin according to the Statutes of Distributions. Chattels are divided into chattels real and chattels personal. Chattels real are those interests in land for which no “real action” (see Action) lies; estates which are less than freehold (estates for years, at will, or by sufferance) are chattels real. Chattels personal are such things as belong immediately to the person of the owner, and for which, if they are injuriously withheld from him, he has no remedy other than by a personal action. Chattels personal are divided into choses in possession and choses in action (see Chose).

A chattel mortgage, in United States law, is a transfer of personal property as security for a debt or obligation in such form that the title to the property will pass to the mortgagee upon the failure of the mortgagor to comply with the terms of the contract. At common law a chattel mortgage might be made without writing, and was valid as between the parties, and even as against third parties if accompanied by possession in the mortgagee, but in most states of the Union legislation now requires a chattel mortgage to be in writing and duly recorded in order to be valid against third parties. At common law a mortgage can be given only of chattels actually in existence and belonging to the mortgagor, though if he acquired title afterwards the mortgage would be good as between the parties, but not as against subsequent purchasers or creditors. In equity, on the other hand, a chattel mortgage, though not good as a conveyance, is valid as an executory agreement.

Goods and chattels is a phrase which, in its widest signification, includes any property other than freehold. The two words, however, have come to be synonymous, and the expression, now practically confined to wills, means merely things movable in possession.

CHATTERIS, a market town in the Wisbech parliamentary division of Cambridgeshire, England, 25½ m. N. by W. of Cambridge by the Great Eastern railway. Pop. of urban district (1901) 4711. It lies in the midst of the flat Fen country. The church of St Peter is principally Decorated; and there are fragments of a Benedictine convent founded in the 10th century and rebuilt after fire in the first half of the 14th. The town has breweries, and engineering and rope-making works. To the north runs the great Forty-foot Drain, also called Vermuyden’s, after the Dutch engineer whose name is associated with the fen drainage works of the middle of the 17th century.

CHATTERJI, BANKIM CHANDRA [Bankimachandra ChattĀradh-yĀya] (1838-1894), Indian novelist, was born in the district of the Twenty-four Parganas in Bengal on the 27th of June 1838, and was by caste a Brahman. He was educated at the Hugli College, at the Presidency College in Calcutta, and at Calcutta University, where he was the first to take the degree of B.A. (1858). He entered the Indian civil service, and served as deputy magistrate in various districts of Bengal, his official services being recognized, on his retirement in 1891, by the title of rai bahadur and the C.I.E. He died on the 8th of April 1894.

Bankim Chandra was beyond question the greatest novelist of India during the 19th century, whether judged by the amount and quality of his writings, or by the influence which they have continued to exercise. His education had brought him into touch with the works of the great European romance writers, notably Sir Walter Scott, and he created in India a school of fiction on the European model. His first historical novel, the Durges-Nandini or Chief’s Daughter, modelled on Scott, made a great sensation in Bengal; and the Kapala-Kundala and Mrinalini, which followed it, established his fame as a writer whose creative imagination and power of delineation had never been surpassed in India. In 1872 he brought out his first social novel, the Biska-Brikkha or Poison Tree, which was followed by others in rapid succession. It is impossible to exaggerate the effect they produced; for over twenty years Bankim Chandra’s novels were eagerly read by the educated public of Bengal, including the Hindu ladies in the zenanas; and though numerous works of fiction are now produced year by year in every province of India, his influence has increased rather than diminished. Of all his works, however, by far the most important from its astonishing political consequences was the Ananda Math, which was published in 1882, about the time of the agitation arising out of the Ilbert Bill. The story deals with the Sannyasi (i.e. fakir or hermit) rebellion of 1772 near Purmea, Tirhut and Dinapur, and its culminating episode is a crushing victory won by the rebels over the united British and Mussulman forces, a success which was not, however, followed up, owing to the advice of a mysterious “physician” who, speaking as a divinely-inspired prophet, advises Satyananda, the leader of “the children of the Mother,” to abandon further resistance, since a temporary submission to British rule is a necessity; for Hinduism has become too speculative and unpractical, and the mission of the English in India is to teach Hindus how to reconcile theory and speculation with the facts of science. The general moral of the Ananda Math, then, is that British rule and British education are to be accepted as the only alternative to Mussulman oppression, a moral which Bankim Chandra developed also in his Dharmatattwa, an elaborate religious treatise in which he explained his views as to the changes necessary in the moral and religious condition of his fellow-countrymen before they could hope to compete on equal terms with the British and Mahommedans. But though the Ananda Math is in form an apology for the loyal acceptance of British rule, it is none the less inspired by the ideal of the restoration, sooner or later, of a Hindu kingdom in India. This is especially evident in the occasional verses in the book, of which the Bande Mataram is the most famous.

As to the exact significance of this poem a considerable controversy has raged. Bande Mataram is the Sanskrit for “Hail to thee, Mother!” or more literally “I reverence thee, Mother!”, and according to Dr G.A. Grierson (The Times, Sept. 12, 1906) it can have no other possible meaning than an invocation of one of the “mother” goddesses of Hinduism, in his opinion Kali “the goddess of death and destruction.” Sir Henry Cotton, on the other hand (ib. Sept. 13, 1906), sees in it merely an invocation of the “mother-land” Bengal, and quotes in support of this view the free translation of the poem by the late W.H. Lee, a proof which, it may be at once said, is far from convincing. But though, as Dr Grierson points out, the idea of a “mother-land” is wholly alien to Hindu ideas, it is quite possible that Bankim Chandra may have assimilated it with his European culture, and the true explanation is probably that given by Mr J.D. Anderson in The Times of September 24, 1906. He points out that in the 11th chapter of the 1st book of the Ananda Math the Sannyasi rebels are represented as having erected, in addition to the image of Kali, “the Mother who Has Been,” a white marble statue of “the Mother that Shall Be,” which “is apparently a representation of the mother-land. 10 The Bande Mataram hymn is apparently addressed to both idols.”

The poem, then, is the work of a Hindu idealist who personified Bengal under the form of a purified and spiritualized Kali. Of its thirty-six lines, partly written in Sanskrit, partly in Bengali, the greater number are harmless enough. But if the poet sings the praise of the “Mother”

he also praises her as “Durga, bearing ten weapons,” and lines 10, 11 and 12 are capable of very dangerous meanings in the mouths of unscrupulous agitators. Literally translated these run, “She has seventy millions of throats to sing her praise, twice seventy millions of hands to fight for her, how then is Bengal powerless?” As S.M. Mitra points out (Indian Problems, London, 1908), this language is the more significant as the Bande Mataram in the novel was the hymn by singing which the Sannyasis gained strength when attacking the British forces.

During Bankim Chandra Chatterji’s lifetime the Bande Mataram, though its dangerous tendency was recognized, was not used as a party war-cry; it was not raised, for instance, during the Ilbert Bill agitation, nor by the students who flocked round the court during the trial of Surendra Nath Banerji in 1883. It has, however, obtained an evil notoriety in the agitations that followed the partition of Bengal. That Bankim Chandra himself foresaw or desired any such use of it is impossible to believe. According to S.M. Mitra, he composed it “in a fit of patriotic excitement after a good hearty dinner, which he always enjoyed. It was set to Hindu music, known as the Mallar-Kawali-Tal. The extraordinarily stirring character of the air, and its ingenious assimilation of Bengali passages with Sanskrit, served to make it popular.”

Circumstances have made the Bande Mataram the most famous and the most widespread in its effects of Bankim Chandra’s literary works. More permanent, it may be hoped, was the wholesome influence he exercised on the number of literary men he gathered round him, who have left their impress on the literature of Bengal. In his earlier years he served his apprenticeship in literature under Iswar Chandra Vidyasagar, the chief poet and satirist of Bengal during the earlier half of the 19th century. Bankim Chandra’s friend and colleague, Dina Bandhu Mitra, was virtually the founder of the modern Bengali drama. Another friend of his, Hem Chandra Banerji, was a poet of recognized merit and talent. And among the younger men who venerated Bankim Chandra, and benefited by his example and advice, may be mentioned two distinguished poets, Nalein Chandra Sen and Rabindra Nath Tagore.

Of Bankim Chandra’s novels some have been translated into English by H.A.D. Phillips and by Mrs M.S. Knight.

CHATTERTON, THOMAS (1752-1770), English poet, was born at Bristol on the 20th of November 1752. His pedigree has a curious significance. The office of sexton of St Mary Redcliffe, at Bristol, one of the most beautiful parish churches in England, had been transmitted for nearly two centuries in the Chatterton family; and throughout the brief life of the poet it was held by his uncle, Richard Phillips. The poet’s father, Thomas Chatterton, was a musical genius, somewhat of a poet, a numismatist, and a dabbler in occult arts. He was one of the sub-chanters of Bristol cathedral, and master of the Pyle Street free school, near Redcliffe church. But whatever hereditary tendencies may have been transmitted from the father, the sole training of the boy necessarily devolved on his mother, who was in the fourth month of her widowhood at the time of his birth. She established a girls’ school, took in sewing and ornamental needlework, and so brought up her two children, a girl and a boy, till the latter attained his eighth year, when he was admitted to Colston’s Charity. But the Bristol blue-coat school, in which the curriculum was limited to reading, writing, arithmetic and the Church Catechism, had little share in the education of its marvellous pupil. The hereditary race of sextons had come to regard the church of St Mary Redcliffe as their own peculiar domain; and, under the guidance of his uncle, the child found there his favourite haunt. The knights, ecclesiastics and civic dignitaries, recumbent on its altar tombs, became his familiar associates; and by and by, when he was able to spell his way through the inscriptions graven on their monuments, he found a fresh interest in certain quaint oaken chests in the muniment room over the porch on the north side of the nave, where parchment deeds, old as the Wars of the Roses, long lay unheeded and forgotten. They formed the child’s playthings almost from his cradle. He learned his first letters from the illuminated capitals of an old musical folio, and learned to read out of a black-letter Bible. He did not like, his sister said, reading out of small books. Wayward, as it seems, almost from his earliest years, and manifesting no sympathy with the ordinary pastimes of children, he was regarded for a time as deficient in intellect. But he was even then ambitious of distinction. His sister relates that on being asked what device he would like painted on a bowl that was to be his, he replied, “Paint me an angel, with wings, and a trumpet, to trumpet my name over the world.”

From his earliest years he was liable to fits of abstraction, sitting for hours in seeming stupor, or yielding after a time to tears, for which he would assign no reason. He had no one near him to sympathize in the strange world of fancy which his imagination had already called into being; and circumstances helped to foster his natural reserve, and to beget that love of mystery which exercised so great an influence on the development of his genius. When the strange child had attained his sixth year his mother began to recognize his capacity; at eight he was so eager for books that he would read and write all day long if undisturbed; and in his eleventh year he had become a contributor to Felix Farley’s Bristol Journal. The occasion of his confirmation inspired some religious poems published in this paper. In 1763 a beautiful cross of curious workmanship, which had adorned the churchyard of St Mary Redcliffe for upwards of three centuries, was destroyed by a churchwarden. The spirit of veneration was strong in the boy, and he sent to the local journal on the 7th of January 1764 a clever satire on the parish Vandal. But his delight was to lock himself in a little attic which he had appropriated as his study; and there, with books, cherished parchments, saved from the loot of the muniment room of St Mary Redcliffe, and drawing materials, the child lived in thought with his 15th-century heroes and heroines. The first of his literary mystifications, the duologue of “Elinoure and Juga,” was written before he was twelve years old, and he showed his poem to the usher at Colston’s hospital, Thomas Phillips, as the work of a 15th-century poet.

Chatterton remained an inmate of Colston’s hospital for upwards of six years, and the slight advantages gained from this scanty education are traceable to the friendly sympathy of Phillips, himself a writer of verse, who encouraged his pupils to write. Three of Chatterton’s companions are named as youths whom Phillips’s taste for poetry stimulated to rivalry; but Chatterton held aloof from these contests, and made at that time no confidant of his own more daring literary adventures. His little pocket-money was spent in borrowing books from a circulating library; and he early ingratiated himself with book collectors, by whose aid he found access to Weever, Dugdale and Collins, as well as to Speght’s edition of Chaucer, Spenser and other books.

His “Rowleian” jargon appears to have been chiefly the result of the study of John Kersey’s Dictionarium Anglo-Britannicum, and Prof. W. W. Skeat seems to think his knowledge of even Chaucer was very slight. His holidays were mostly spent at his mother’s house; and much of them in the favourite retreat of his attic study there. He had already conceived the romance of Thomas Rowley, an imaginary monk of the 15th century, and lived for the most part in an ideal world of his own, in that elder time when Edward IV. was England’s king, and Master William Canynge—familiar to him among the recumbent effigies in Redcliffe church—still ruled in Bristol’s civic chair. Canynge is represented as an enlightened patron of literature, and Rowley’s dramatic interludes were written for 11 performance at his house. In order to escape a marriage urged by the king, Canynge retired to the college of Westbury in Gloucestershire, where he enjoyed the society of Rowley, and eventually became dean of the institution. In “The Storie of William Canynge,” one of the shorter pieces of his ingenious romance, his early history is recorded.

This beautiful picture of the childhood of the ideal patron of Rowley is in reality that of the poet himself—“the fate-marked babe,” with his wondrous child-genius, and all his romantic dreams realized. The literary masquerade which thus constituted the life-dream of the boy was wrought out by him in fragments of prose and verse into a coherent romance, until the credulous scholars and antiquaries of his day were persuaded into the belief that there had lain in the parish chest of Redcliffe church for upwards of three centuries, a collection of MSS. of rare merit, the work of Thomas Rowley, an unknown priest of Bristol in the days of Henry VI. and his poet laureate, John Lydgate.

Among the Bristol patrons of Chatterton were two pewterers, George Catcott and his partner Henry Burgum. Catcott was one of the most zealous believers in Rowley, and continued to collect his reputed writings long after the death of their real author. On Burgum, who had risen in life by his own exertions, the blue-coat boy palmed off the de Bergham pedigree, and other equally apocryphal evidences of the pewterer’s descent from an ancestry old as the Norman Conquest. The de Bergham quartering, blazoned on a piece of parchment doubtless recovered from the Redcliffe muniment chest, was itself supposed to have lain for centuries in that ancient depository. The pedigree was professedly collected by Chatterton from original records, including “The Rowley MSS.” The pedigree still exists in Chatterton’s own handwriting, copied into a book in which he had previously transcribed portions of antique verse, under the title of “Poems by Thomas Rowley, priest of St. John’s, in the city of Bristol”; and in one of these, “The Tournament,” Syrr Johan de Berghamme plays a conspicuous part. The ennobled pewterer rewarded Chatterton with five shillings, and was satirized for this valuation of a noble pedigree in some of Chatterton’s latest verse.

On the 1st of July 1767, Chatterton was transferred to the office of John Lambert, attorney, to whom he was bound apprentice as a clerk. There he was left much alone; and after fulfilling the routine duties devolving on him, he found leisure for his own favourite pursuits. An ancient stone bridge on the Avon, built in the reign of Henry II., and altered by many later additions into a singularly picturesque but inconvenient thoroughfare, had been displaced by a structure better adapted to modern requirements. In September 1768, when Chatterton was in the second year of his apprenticeship, the new bridge was partially opened for traffic. Shortly afterwards the editor of Felix Farley’s Journal received from a correspondent, signing himself Dunelmus Bristoliensis, a “description of the mayor’s first passing over the old bridge,” professedly derived from an ancient MS. William Barrett, F.S.A., surgeon and antiquary, who was then accumulating materials for a history of Bristol, secured the original manuscript, which is now preserved in the British Museum, along with other Chatterton MSS., most of which were ultimately incorporated by the credulous antiquary into a learned quarto volume, entitled the History and Antiquities of the City of Bristol, published nearly twenty years after the poet’s death. It was at this time that the definite story made its appearance—over which critics and antiquaries wrangled for nearly a century—of numerous ancient poems and other MSS. taken by the elder Chatterton from a coffer in the muniment room of Redcliffe church, and transcribed, and so rescued from oblivion, by his son. The pieces include the “Bristowe Tragedie, or the Dethe of Syr Charles Bawdin,” a ballad celebrating the death of the Lancastrian knight, Charles Baldwin; “Ælla,” a “Tragycal Enterlude,” as Chatterton styles it, but in reality a dramatic poem of sustained power and curious originality of structure; “Goddwyn,” a dramatic fragment; “Tournament,” “Battle of Hastings,” “The Parliament of Sprites,” “Balade of Charitie,” with numerous shorter pieces, forming altogether a volume of poetry, the rare merit of which is indisputable, wholly apart from the fact that it was the production of a mere boy. Unfortunately for him, his ingenious romance had either to be acknowledged as his own creation, and so in all probability be treated with contempt, or it had to be sustained by the manufacture of spurious antiques. To this accordingly Chatterton resorted, and found no difficulty in gulling the most learned of his credulous dupes with his parchments.

The literary labours of the boy, though diligently pursued at his desk, were not allowed to interfere with the duties of Mr Lambert’s office. Nevertheless the Bristol attorney used to search his apprentice’s drawer, and tear up any poems or other manuscripts that he could lay his hands upon; so that it was only during the absences of Mr Lambert from Bristol that he was able to expend his unemployed time in his favourite pursuits. But repeated allusions, both by Chatterton and others, seem to indicate that such intervals of freedom were of frequent occurrence. Some of his modern poems, such as the piece entitled “Resignation,” are of great beauty; and these, with the satires, in which he took his revenge on all the local celebrities whose vanity or meanness had excited his ire, are alone sufficient to fill a volume. The Catcotts, Burgum, Barrett and others of his patrons, figure in these satires, in imprudent yet discriminating caricature, along with mayor, aldermen, bishop, dean and other notabilities of Bristol. Towards Lambert his feelings were of too keen a nature to find relief in such sarcasm.

In December 1768, in his seventeenth year, he wrote to Dodsley, the London publisher, offering to procure for him “copies of several ancient poems, and an interlude, perhaps the oldest dramatic piece extant, wrote by one Rowley, a priest in Bristol, who lived in the reigns of Henry VI. and Edward IV.” To this letter he appended the initials of his favourite pseudonym, Dunelmus Bristoliensis, but directed the answer to be sent to the care of Thomas Chatterton, Redcliffe Hill, Bristol. To this, as well as to another letter enclosing an extract from the tragedy of “Ælla,” no answer appears to have been returned. Chatterton, conceiving the idea of finding sympathy and aid at the hand of some modern Canynge, bethought him of Horace Walpole, who not only indulged in a medieval renaissance of his own, but was the reputed author of a spurious antique in the Castle of Otranto. He wrote to him offering him a document entitled “The Ryse of Peyncteyne yn Englande, wroten by T. Rowleie, 1469, for Mastre Canynge,” accompanied by notes which included specimens of Rowley’s poetry. To this Walpole replied with courteous acknowledgments. He characterized the verses as “wonderful for their harmony and spirit,” and added, “Give me leave to ask you where Rowley’s poems are to be had? I should not be sorry to print them; or at least a specimen of them, if they have never been printed.” Chatterton replied, enclosing additional specimens of antique verse, and telling Walpole that he was the son of a poor widow, and clerk to an attorney, but had a taste for more refined studies; and he hinted a wish that he might help him to some more congenial occupation. Walpole’s manner underwent an abrupt change. The specimens of verse had been submitted to his friends Gray and Mason, the poets, and pronounced modern. They did not thereby forfeit the wonderful harmony and spirit which Walpole had already professed to recognize in them. But he now coldly advised the boy to stick to the attorney’s office; and “when he should have made a fortune,” he might betake himself to more favourite 12 studies, Chatterton had to write three times before he recovered his MSS. Walpole has been loaded with more than his just share of responsibility for the fate of the unhappy poet, of whom he admitted when too late, “I do not believe there ever existed so masterly a genius.”

Chatterton now turned his attention to periodical literature and politics, and exchanged Felix Farley’s Bristol Journal for the Town and County Magazine and other London periodicals. Assuming the vein of Junius—then in the full blaze of his triumph—he turned his pen against the duke of Grafton, the earl of Bute, and the princess of Wales. He had just despatched one of his political diatribes to the Middlesex Journal, when he sat down on Easter Eve, I7th April 1770, and penned his “Last Will and Testament,” a strange satirical compound of jest and earnest, in which he intimated his intention of putting an end to his life the following evening. Among his satirical bequests, such as his “humility” to the Rev. Mr Camplin, his “religion” to Dean Barton, and his “modesty” along with his “prosody and grammar” to Mr Burgum, he leaves “to Bristol all his spirit and disinterestedness, parcels of goods unknown on its quay since the days of Canynge and Rowley.” In more genuine earnestness he recalls the name of Michael Clayfield, a friend to whom he owed intelligent sympathy. The will was probably purposely prepared in order to frighten his master into letting him go. If so, it had the desired effect. Lambert cancelled his indentures; his friends and acquaintance made him up a purse; and on the 25th or 26th of the month he arrived in London.

Chatterton was already known to the readers of the Middlesex Journal as a rival of Junius, under the nom de plume of Decimus. He had also been a contributor to Hamilton’s Town and County Magazine, and speedily found access to the Freeholder’s Magazine, another political miscellany strong for Wilkes and liberty. His contributions were freely accepted; but the editors paid little or nothing for them. He wrote in the most hopeful terms to his mother and sister, and spent his first earnings in buying gifts for them. His pride and ambition were amply gratified by the promises and interested flattery of editors and political adventurers; Wilkes himself had noted his trenchant style, “and expressed a desire to know the author”; and Lord Mayor Beckford graciously acknowledged a political address of his, and greeted him “as politely as a citizen could.” But of actual money he received but little. He was extremely abstemious, his diligence was great, and his versatility wonderful. He could assume the style of Junius or Smollett, reproduce the satiric bitterness of Churchill, parody Macpherson’s Ossian, or write in the manner of Pope, or with the polished grace of Gray and Collins. He wrote political letters, eclogues, lyrics, operas and satires, both in prose and verse. In June 1770—after Chatterton had been some nine weeks in London—he removed from Shoreditch, where he had hitherto lodged with a relative, to an attic in Brook Street, Holborn. But for most of his productions the payment was delayed; and now state prosecutions of the press rendered letters in the Junius vein no longer admissible, and threw him back on the lighter resources of his pen. In Shoreditch, as in his lodging at the Bristol attorney’s, he had only shared a room; but now, for the first time, he enjoyed uninterrupted solitude. His bed-fellow at Mr Walmsley’s, Shoreditch, noted that much of the night was spent by him in writing; and now he could write all night. The romance of his earlier years revived, and he transcribed from an imaginary parchment of the old priest Rowley his “Excelente Balade of Charitie.” This fine poem, perversely disguised in archaic language, he sent to the editor of the Town and County Magazine, and had it rejected.

The high hopes of the sanguine boy had begun to fade. He had not yet completed his second month in London, and already failure and starvation stared him in the face. Mr Cross, a neighbouring apothecary, repeatedly invited him to join him at dinner or supper; but he refused. His landlady also, suspecting his necessity, pressed him to share her dinner, but in vain. “She knew,” as she afterwards said, “that he had not eaten anything for two or three days.” But he was offended at her urgency, and assured her that he was not hungry. The note of his actual receipts, found in his pocket-book after his death, shows that Hamilton, Fell and other editors who had been so liberal in flattery, had paid him at the rate of a shilling for an article, and somewhat less than eightpence each for his songs; while much which had been accepted was held in reserve, and still unpaid for. The beginning of a new month revealed to him the indefinite postponement of the publication and payment of his work. He had wished, according to his foster-mother, to study medicine with Barrett; in his desperation he now reverted to this, and wrote to Barrett for a letter to help him to an opening as a surgeon’s assistant on board an African trader. He appealed also to Mr Catcott to forward his plan, but in vain. On the 24th of August 1770, he retired for the last time to his attic in Brook Street, carrying with him the arsenic which he there drank, after tearing into fragments whatever literary remains were at hand.

He was only seventeen years and nine months old; but the best of his numerous productions, both in prose and verse, require no allowance to be made for the immature years of their author, when comparing him with the ablest of his contemporaries. He pictures Lydgate, the monk of Bury St Edmunds, challenging Rowley to a trial at versemaking, and under cover of this fiction, produces his “Songe of Ælla,” a piece of rare lyrical beauty, worthy of comparison with any antique or modern production of its class. Again, in his “Tragedy of Goddwyn,” of which only a fragment has been preserved, the “Ode to Liberty,” with which it abruptly closes, may claim a place among the finest martial lyrics in the language. The collection of poems in which such specimens occur furnishes by far the most remarkable example of intellectual precocity in the whole history of letters. Collins, Burns, Keats, Shelley and Byron all awaken sorrow over the premature arrestment of their genius; but the youngest of them survived to his twenty-fifth year, while Chatterton was not eighteen when he perished in his miserable garret. The death of Chatterton attracted little notice at the time; for the few who then entertained any appreciative estimate of the Rowley poems regarded him as their mere transcriber. He was interred in a burying-ground attached to Shoe Lane Workhouse, in the parish of St Andrew’s, Holborn, which has since been converted into a site for Farringdon Market. There is a discredited story that the body of the poet was recovered, and secretly buried by his uncle, Richard Phillips, in Redcliffe Churchyard. There a monument has since been erected to his memory, with the appropriate inscription, borrowed from his “Will,” and so supplied by the poet’s own pen—“To the memory of Thomas Chatterton. Reader! judge not. If thou art a Christian, believe that he shall be judged by a Superior Power. To that Power only is he now answerable.”

CHATTI, an ancient German tribe inhabiting the upper reaches of the rivers Weser, Eder, Fulda and Werra, a district approximately corresponding to Hesse-Cassel, though probably somewhat more extensive. They frequently came into conflict with the Romans during the early years of the 1st century. Eventually they formed a portion of the Franks and were incorporated in the kingdom of Clovis probably with the Ripuarii, at the beginning of the 6th century.

Tacitus, Annals, i. 2, II, 12, 13; Germania, 30-31; Strabo p. 291 f.

CHAUCER, GEOFFREY (? 1340-1400), English poet. The name Chaucer, a French form of the Latin calcearius, a shoe-maker, is found in London and the eastern counties as early as the second half of the 13th century. Some of the London Chaucers lived in Cordwainer Street, in the shoemakers’ quarter; several of them, however, were vintners, and among others the poet’s father John, and probably also his grandfather Robert. Legal pleadings inform us that in December 1324 John Chaucer was not much over twelve years old, and that he was still unmarried Life. in 1328, the year which used to be considered that of Geoffrey’s birth.The poet was probably born from eight to twelve years later, since in 1386, when giving evidence in Sir Richard le Scrope’s suit against Sir Robert Grosvenor as to the right to bear certain arms, he was set down as “del age de xl ans et plus, armeez par xxvij ans.” At a later date, and probably at the time of the poet’s birth, his father lived in Thames Street, and had to wife a certain Agnes, niece of Hamo de Compton, whom we may regard as Geoffrey Chaucer’s mother. In 1357 Geoffrey is found, apparently as a lad, in the service of Elizabeth, countess of Ulster, wife of Lionel, duke of Clarence, entries in two leaves of her household accounts, accidentally preserved, showing that she paid in April, May and December various small sums for his clothing and expenses. In 1359, as we learn from his deposition in the Scrope suit, Chaucer went to the war in France. At some period of the campaign he was at “Retters,” i.e. Rethel, near Reims, and subsequently had the ill luck to be taken prisoner. On the 1st of March 1360 the king contributed £16 to his ransom, and by a year or two later Chaucer must have entered the royal service, since on the 20th of June 1367 Edward granted him a pension of twenty marks for his past and future services. A pension of ten marks had been granted by the king the previous September to a Philippa Chaucer for services to the queen as one of her “domicellae” or “damoiselles,” and it seems probable that at this date Chaucer was already married and this Philippa his wife, a conclusion which used to be resisted on the ground of allusions in his early poems to a hopeless love-affair, now reckoned part of his poetical outfit. Philippa is usually said to have been one of two daughters of a Sir Payne Roet, the other being Katherine, who after the death of her first husband, Sir Hugh de Swynford, in 1372, became governess to John of Gaunt’s children, and subsequently his mistress and (in 1396) his wife. It is possible that Philippa was sister to Sir Hugh and sister-in-law to Katherine. In either case the marriage helps to account for the favour subsequently shown to Chaucer by John of Gaunt.

In the grant of his pension Chaucer is called “dilectus vallectus noster,” our beloved yeoman; before the end of 1368 he had risen to be one of the king’s esquires. In September of the following year John of Gaunt’s wife, the duchess Blanche, died at the age of twenty-nine, and Chaucer wrote in her honour The Book of the Duchesse, a poem of 1334 lines in octosyllabic couplets, the first of his undoubtedly genuine works which can be connected with a definite date. In June 1370 he went abroad on the king’s service, though on what errand, or whither it took him, is not known. He was back probably some time before Michaelmas, and seems to have remained in England till the 1st of December 1372, when he started, with an advance of 100 marks in his pocket, for Italy, as one of the three commissioners to treat with the Genoese as to an English port where they might have special facilities for trade. The accounts which he delivered on his return on the 23rd of May 1373 show that he had also visited Florence on the king’s business, and he probably went also to Padua and there made the acquaintance of Petrarch.

In the second quarter of 1374 Chaucer lived in a whirl of prosperity. On the 23rd of April the king granted him a pitcher of wine daily, subsequently commuted for an annuity of 20 marks. From John of Gaunt, who in August 1372 had granted Philippa Chaucer £10 a year, he himself now received (June 13) a like annuity in reward for his own and his wife’s services. On the 8th of June he was appointed Comptroller of the Custom and Subsidy of Wools, Hides and Woodfells and also of the Petty Customs of Wine in the Port of London. A month before this appointment, and probably in anticipation of it, he took (May 10, 1374) a lease for life from the city of London of the dwelling-house above the gate of Aldgate, and here he lived for the next twelve years. His own and his wife’s income now amounted to over £60, the equivalent of upwards of £1000 in modern money. In the next two years large windfalls came to him in the form of two wardships of Kentish heirs, one of whom paid him £104, and a grant of £71: 4: 6; the value of some confiscated wool. In December 1376 he was sent abroad on the king’s service in the retinue of Sir John Burley; in February 1377 he was sent to Paris and Montreuil in connexion probably with the peace negotiations between England and France, and at the end of April (after a reward of £20 for his good services) he was again despatched to France.

On the accession of Richard II. Chaucer was confirmed in his offices and pensions. In January 1378 he seems to have been in France in connexion with a proposed marriage between Richard and the daughter of the French king; and on the 28th of May of the same year he was sent with Sir Edward de Berkeley to the lord of Milan and Sir John Hawkwood to treat for help in the king’s wars, returning on the 19th of September. This was his last diplomatic journey, and the close of a period of his life generally considered to have been so unprolific of poetry that little beyond the Clerk’s “Tale of Grisilde,” one or two other of the stories afterwards included in the Canterbury Tales, and a few short poems, are attributed to it, though the poet’s actual absences from England during the eight years amount to little more than eighteen months. During the next twelve or fifteen years there is no question that Chaucer was constantly engaged in literary work, though for the first half of them he had no lack of official employment. Abundant favour was shown him by the new king. He was paid £22 as a reward for his later missions in Edward III.’s reign, and was allowed an annual gratuity of 10 marks in addition to his pay of £10 as comptroller of the customs of wool. In April 1382 a new comptrollership, that of the petty customs in the Port of London, was given him, and shortly after he was allowed to exercise it by deputy, a similar licence being given him in February 1385, at the instance of the earl of Oxford, as regards the comptrollership of wool. In October 1385 Chaucer was made a justice of the peace for Kent. In February 1386 we catch a glimpse of his wife Philippa being admitted to the fraternity of Lincoln cathedral in the company of Henry, earl of 14 Derby (afterwards Henry IV.), Sir Thomas de Swynford and other distinguished persons. In August 1386 he was elected one of the two knights of the shire for Kent, and with this dignity, though it was one not much appreciated in those days, his good fortune reached its climax. In December of the same year he was superseded in both his comptrollerships, almost certainly as a result of the absence of his patron, John of Gaunt, in Spain, and the supremacy of the duke of Gloucester. In the following year the cessation of Philippa’s pension suggests that she died between Midsummer and Michaelmas. In May 1388 Chaucer surrendered to the king his two pensions of 20 marks each, and they were re-granted at his request to one John Scalby. The transaction was unusual and probably points to a pressing need for ready money, nor for the next fourteen months do we know of any source of income possessed by Chaucer beyond his annuity of £10 from John of Gaunt.

In July 1389, after John of Gaunt had returned to England, and the king had taken the government into his own hands, Chaucer was appointed clerk of the works at various royal palaces at a salary of two shillings a day, or over £31 a year, worth upwards of £500 present value. To this post was subsequently added the charge of some repairs at St George’s Chapel, Windsor. He was also made a commissioner to maintain the banks of the Thames between Woolwich and Greenwich, and was given by the earl of March (grandson of Lionel, duke of Clarence, his old patron) a sub-forestership at North Petherton, Devon, obviously a sinecure. While on the king’s business, in September 1390, Chaucer was twice robbed by highwaymen, losing £20 of the king’s money. In June 1391 he was superseded in his office of clerk of the works, and seems to have suffered another spell of misfortune, of which the first alleviation came in January 1393 when the king made him a present of £10. In February 1394 he was granted a new pension of £20. It is possible, also, that about this time, or a little later, he was in the service of the earl of Derby. In 1397 he received from King Richard a grant of a butt of wine yearly. For this he appears to have asked in terms that suggest poverty, and in May 1398 he obtained letters of protection against his creditors, a step perhaps rendered necessary by an action for debt taken against him earlier in the year. On the accession of Henry IV. a new pension of 40 marks was conferred on Chaucer (13th of October 1399) and Richard II.’s grants were formally confirmed. Henry himself, however, was probably straitened for ready money, and no instalment of the new pension was paid during the few months of his reign that the poet lived. Nevertheless, on the strength of his expectations, on the 24th of December 1399 he leased a tenement in the garden of St Mary’s Chapel, Westminster, and it was probably here that he died, on the 25th of the following October. He was buried in Westminster Abbey, and his tomb became the nucleus of what is now known as Poets’ Corner.

The portrait of Chaucer, which the affection of his disciple, Thomas Hoccleve, caused to be painted in a copy of the latter’s Regement of Princes (now Harleian MS. 4866 in the British Museum), shows him an old man with white hair; he has a fresh complexion, grey eyes, a straight nose, a grey moustache and a small double-pointed beard. His dress and hood are black, and he carries in his hands a string of beads. We may imagine that it was thus that during the last months of his life he used to walk about the precincts of the Abbey.

Henry IV.’s promise of an additional pension was doubtless elicited by the Compleynt to his Purs, in the envoy to which Chaucer addresses him as the “conquerour of Brutes Works. Albioun.” Thus within the last year of his life the poet was still writing. Nevertheless, as early as 1393-1394, in lines to his friend Scogan, he had written as if his day for poetry were past, and it seems probable that his longer poems were all composed before this date. In the preceding fifteen—or, if another view be taken, twenty—years, his literary activity was very great, and with the aid of the lists of his works which he gives in the Legende of Good Women (lines 414-431), and the talk on the road which precedes the “Man of Law’s Tale” (Canterbury Tales, B. 46-76), the order in which his main works were written can be traced with approximate certainty,1 while a few both of these and of the minor poems can be connected with definite dates.

The development of his genius has been attractively summed up as comprised in three stages, French, Italian and English, and there is a rough approximation to the truth in this formula, since his earliest poems are translated from the French or based on French models, and the two great works of his middle period are borrowed from the Italian, while his latest stories have no such obvious and direct originals and in their humour and freedom anticipate the typically English temper of Henry Fielding. But Chaucer’s indebtedness to French poetry was no passing phase. For various reasons—a not very remote French origin of his own family may be one of them—he was in no way interested in older English literature or in the work of his English contemporaries, save possibly that of “the moral Gower.” On the other hand he knew the Roman de la rose as modern English poets know Shakespeare, and the full extent of his debt to his French contemporaries, not merely in 1369, but in 1385 and in 1393 (the dates are approximate), is only gradually being discovered. To be in touch throughout his life with the best French poets of the day was much for Chaucer. Even with their stimulus alone he might have developed no small part of his genius. But it was his great good fortune to add to this continuing French influence, lessons in plot and construction derived from Boccaccio’s Filostrato and Teseide, as well as some glimpses of the higher art of the Divina Commedia. He shows acquaintance also with one of Petrarch’s sonnets, and though, when all is said, the Italian books with which he can be proved to have been intimate are but few, they sufficed. His study of them was but an episode in his literary life, but it was an episode of unique importance. Before it began he had already been making his own artistic experiments, and it is noteworthy that while he learnt so much from Boccaccio he improved on his originals as he translated them. Doubtless his busy life in the service of the crown had taught him self-confidence, and he uses his Italian models in his own way and with the most triumphant and assured success. When he had no more Italian poems to adapt he had learnt his lesson. The art of weaving a plot out of his own imagination was never his, but he could take what might be little more than an anecdote and lend it body and life and colour with a skill which has never been surpassed.

The most direct example of Chaucer’s French studies is his translation of Le Roman de la rose, a poem written in some 4000 lines by Guillaume Lorris about 1237 and extended to over 22,000 by Jean Clopinel, better known as Jean de Meun, forty years later. We know from Chaucer himself that he translated this poem, and the extant English fragment of 7698 lines was generally assigned to him from 1532, when it was first printed, till its authorship was challenged in the early years of the Chaucer Society. The ground of this challenge was its wide divergence from Chaucer’s practice in his undoubtedly genuine works as to certain niceties of rhyme, notable as to not rhyming words ending in -y with others ending -ye. It was subsequently discovered, however, that the whole fragment was divisible linguistically into three portions, of which the first and second end respectively at lines 1705 and 5810, and that in the first of these three sections the variations from Chaucer’s accepted practice are insignificant. Lines 1-1705 have therefore been provisionally accepted as Chaucer’s, and the other two fragments as the work of unknown translators (James I. of Scotland has been suggested as one of them), which somehow came to be pieced together. If, however, the difficulties in the way of this theory are less than those which confront any other, they are still considerable, and the question can hardly be treated as closed.

While our knowledge of Chaucer’s Romaunt of the Rose is in this unsatisfactory state, another translation of his from the French, the Book of the Lyon (alluded to in the “Retraction” found, in some manuscripts, at the end of the Canterbury Tales), which must certainly have been taken from Guillaume 15 Machault’s Le Dit du lion, has perished altogether. The strength of French influence on Chaucer’s early work may, however, be amply illustrated from the first of his poems with which we are on sure ground, the Book of the Duchesse, or, as it is alternatively called, the Deth of Blaunche. Here not only are individual passages closely imitated from Machault and Froissart, but the dream, the May morning, and the whole machinery of the poem are taken over from contemporary French conventions. But even at this stage Chaucer could prove his right to borrow by the skill with which he makes his materials serve his own purpose, and some of the lines in the Deth of Blaunche are among the most tender and charming he ever wrote.

Chaucer’s A.B.C., a poem in honour of the Blessed Virgin, of which the stanzas begin with the successive letters of the alphabet, is another early example of French influence. It is taken from the Pèlerinage de la vie humaine, written by Guillaume de Deguilleville about 1330. The occurrence of some magnificent lines in Chaucer’s version, combined with evidence that he did not yet possess the skill to translate at all literally as soon as rhymes had to be considered, accounts for this poem having been dated sometimes earlier than the Book of the Duchesse, and sometimes several years later. With it is usually moved up and down, though it should surely be placed in the ’seventies, the Compleynt to Pity, a fine poem which yet, from its slight obscurity and absence of Chaucer’s usual ease, may very well some day prove to be a translation from the French.

While Chaucer thus sought to reproduce both the matter and the style of French poetry in England, he found other materials in popular Latin books. Among his lost works are renderings of “Origenes upon the Maudeleyne,” and of Pope Innocent III. on “The Wreced Engendring of Mankinde” (De miseria conditionis humanae). He must have begun his attempts at straightforward narrative with the Lyf of Seynt Cecyle (the weakest of all his works, the second Nun’s Tale in the Canterbury series) from the Legenda Aurea of Jacobus de Voragine, and the story of the patience of Grisilde, taken from Petrarch’s Latin version of a tale by Boccaccio. In both of these he condenses a little, but ventures on very few changes, though he lets his readers see his impatience with his originals. In his story of Constance (afterwards ascribed to the Man of Law), taken from the Anglo-Norman chronicle of Nicholas Trivet, written about 1334, we find him struggling to put some substance into another weak tale, but still without the courage to remedy its radical faults, though here, as with Grisilde, he does as much for his heroine as the conventional exaltation of one virtue at a time permitted. It is possible that other tales which now stand in the Canterbury series were written originally at this period. What is certain is that at some time in the ’seventies three or four Italian poems passed into Chaucer’s possession, and that he set to work busily to make use of them. One of the most interesting of the poems reclaimed for him by Professor Skeat is a fragmentary “Compleynt,” part of which is written in terza rima. While he thus experimented with the metre of the Divina Commedia, he made his first attempt to use the material provided by Boccaccio’s Teseide in another fragment of great interest, that of Quene Anelida and Fals Arcyte. More than a third of this is taken up with another, and quite successful, metrical experiment in Anelida’s “compleynt,” but in the introduction of Anelida herself Chaucer made the first of his three unsuccessful efforts to construct a plot for an important poem out of his own head, and the fragment which begins so well breaks off abruptly at line 357.

For a time the Teseide seems to have been laid aside, and it was perhaps at this moment, in despondency at his failure, that Chaucer wrote his most important prose work, the translation of the De Consolatione Philosophiae of Boethius. Reminiscences of this helped to enrich many of his subsequent poems, and inspired five of his shorter pieces (The Former Age, Fortune, Truth, Gentilesse and Lak of Stedfastnesse), but the translation itself was only a partial success. To borrow his own phrase, his “Englysh was insufficient” to reproduce such difficult Latin. The translation is often barely intelligible without the original, and it is only here and there that it flows with any ease or rhythm.

If Chaucer felt this himself he must have been speedily consold by achieving in Troilus and Criseyde his greatest artistic triumph. Warned by his failure in Anelida and Arcyte, he was content this time to take his plot unaltered from the Filostrato, and to follow Boccaccio step by step through the poem. But he did not follow him as a mere translator. He had done his duty manfully for the saints “of other holinesse” in Cecyle, Grisilde and Constance, whom he was forbidden by the rules of the game to clothe with complete flesh and blood. In this great love-story there were no such restrictions, and the characters which Boccaccio’s treatment left thin and conventional became in Chaucer’s hands convincingly human. No other English poem is so instinct with the glory and tragedy of youth, and in the details of the story Chaucer’s gifts of vivid colouring, of humour and pity, are all at their highest.

An unfortunate theory that the reference in the Legends of Good Women to “al the love of Palamon and Arcyte” is to a hypothetical poem in seven-line stanzas on this theme, which Chaucer is imagined, when he came to plan the Canterbury Tales, to have suppressed in favour of a new version in heroic couplets, has obscured the close connexion in temper and power between what we know as the “Knight’s Tale” and the Troilus. The poem may have been more or less extensively revised before, with admirable fitness, it was assigned to the Knight, but that its main composition can be separated by several years from that of Troilus is aesthetically incredible. Chaucer’s art here again is at its highest. He takes the plot of Boccaccio’s Teseide, but only as much of it as he wants, and what he takes he heightens and humanizes with the same skill which he had shown in transforming the Filostrato. Of the individual characters Theseus himself, the arbiter of the plot, is most notably developed; Emilie and her two lovers receive just as much individuality as they will bear without disturbing the atmosphere of romance. The whole story is pulled together and made more rapid and effective. A comparison of almost any scene as told by the two poets suffices to show Chaucer’s immense superiority. At some subsequent period the “Squire’s Tale” of Cambuscan, the fair Canacee and the Horse of Brass, was gallantly begun in something of the same key, but Chaucer took for it more materials than he could use, and for lack of the help of a leader like Boccaccio he was obliged to leave the story, in Milton’s phrase, “half-told,” though the fragment written certainly takes us very much less than half-way.

Meanwhile, in connexion (as is reasonably believed) with the betrothal or marriage of Anne of Bohemia to Richard II. (i.e. about 1381-1382), Chaucer had brought to a successful completion the Parlement of Foules, a charming sketch of 699 lines, in which the other birds, on Saint Valentine’s day, counsel the “Formel Egle” on her choice of a mate. His success here, as in the case of the Deth of Blaunche the Duchesse, was due to the absence of any need for a climax; and though the materials which he borrowed were mainly Latin (with some help from passages of the Teseide not fully needed for Palamon and Arcyte) his method of handling them would have been quite approved by his friends among the French poets. A more ambitious venture, the Hous of Fame, in which Chaucer imagines himself borne aloft by an eagle to Fame’s temple, describes what he sees and hears there, and then breaks off in apparent inability to get home, shows a curious mixture of the poetic ideals of the Roman de la rose and reminiscences of the Divina Commedia.

As the Hous of Fame is most often remembered and quoted for the personal touches and humour of Chaucer’s conversation with the eagle, so the most-quoted passages in the Prologue to the Legende of Good Women are those in which Chaucer professes his affection for the daisy, and the attack on his loyalty by Cupid and its defence by Alceste. Recent discoveries have shown, however, that (besides obligations to Machault) some of the touches about the daisy and the controversy between the partisans of the Flower and of the Leaf are snatches from poems by his friends Froissart and Deschamps, which Chaucer takes up 16 and returns to them with pretty compliments, and that he was indebted to Froissart for some of the framework of his poem.2 Both of the two versions of the Prologue to the Legende are charming, and some of the tales, notably that of Cleopatra, rank with Chaucer’s best work. When, however, he had written eight and part of the ninth he tired of his scheme, which was planned to celebrate nineteen of Cupid’s faithful “saints,” with Alcestis as their queen. With his usual hopefulness he had overlooked the risk of monotony, which obviously weighed heavily on him ere he broke off, and the loss of the other ten stories is less to be regretted than that of the celebration of Alceste, and a possible epilogue which might have exceeded in charm the Prologue itself.

Chaucer’s failure to complete the scheme of the Legende of Good Women may have been partly due to the attractions of the Canterbury Tales, which were probably taken up in Canterbury Tales. immediate succession to it. His guardianship of two Kentish wards, his justiceship of the peace, his representing the county in the parliament of 1386, his commissionership of the river-bank between Greenwich and Woolwich, all make it easy to understand his dramatic use of the merry crowds he saw on the Canterbury road, without supposing him to have had recourse to Boccaccio’s Decamerone, a book which there is no proof of his having seen. The pilgrims whom he imagines to have assembled at the Tabard Inn in Southwark, where Harry Bailey was host, are said to have numbered “wel nyne and twenty in a company,” and the Prologue gives full-length sketches of a Knight, a Squire (his son), and their Yeoman; of a Prioress, Monk, Friar, Oxford Clerk, and Parson, with two disreputable hangers-on of the church, a Summoner and Pardoner; of a Serjeant-at-Law and a Doctor of Physic, and of a Franklin, or country gentleman, Merchant, Shipman, Miller, Cook, Manciple, Reeve, Ploughman (the Parson’s brother) and the ever-famous Wife of Bath. Five London burgesses are described in a group, and a Nun and Priest3 are mentioned as in attendance on the Prioress. Each of these, with Chaucer himself making the twenty-ninth, was pledged to tell two tales, but including one second attempt and a tale told by the Yeoman of a Canon, who overtakes the pilgrims on the road, we have only twenty finished stories, two unfinished and two interrupted ones. As in the case of the Legende of Good Women, our loss is not so much that of the additional stories as of the completed framework. The wonderful character sketches of the Prologue are carried yet farther by the Talks on the Road which link the different tales, and two of these Talks, in which the Wife of Bath and the Pardoner respectively edify the company, have the importance of separate Tales, but between the Tales that have come down to us there are seven links missing,4 and it was left to a later and weaker hand to narrate, in the “Tale of Beryn,” the adventures of the pilgrims at Canterbury.

The reference to the Lyf of Seynt Cecyle in the Prologue to the Legende of Good Women gives external proof that Chaucer included earlier work in the scheme of the Canterbury Tales, and mention has been made of other stories which are indisputably early. In the absence of any such metrical tests as have proved useful in the case of Shakespeare, the dates at which several of the Tales were composed remain doubtful, while in the case of at least two, the Clerk’s tale of Grisilde and the Monk’s tragedies, there is evidence of early work being revised and supplemented. It is fortunately impossible to separate the prologue to the charmingly told story of “yonge Hugh of Lincoln” from the tale itself, and with the “quod sche” in the second line as proof that Chaucer was here writing specially for his Prioress we are forbidden to limit the new stories to any one metre or tone. There can be no doubt, however, that what may be called the Tales of the Churls (Miller, Reeve, Summoner, Friar, &c.), and the conversational outpourings of the Pardoner and Wife of Bath, form, with the immortal Prologue, the most important and distinctive additions to the older work. In these, and in the Pardoner’s story of Death and the Three Revellers, and the Nun’s Priest’s masterly handling of the fable of the Cock and Fox, both of them free from the grossness which marks the others, Chaucer takes stories which could have been told in a short page of prose and elaborates them with all the skill in narration which he had sedulously cultivated. The conjugal reminiscences of the Wife of Bath and the Reeve’s Tale with its abominable climax (lightened a little by Aleyn’s farewell, lines 316-319) are among the great things in Chaucer, as surely as Troilus, and Palamon and Arcyte and the Prologue. They help notably to give him the width of range which may certainly be claimed for him.

In or soon after 1391 Chaucer wrote in prose for an eleven-year-old reader, whom he addresses as “Litel Lowis my son,” a treatise on the use of the Astrolabe, its short prologue being the prettiest specimen of his prose. The wearisome tale of “Melibee and his wyf Prudence,” which was perhaps as much admired in English as it had been in Latin and French, may have been translated at any time. The sermon on Penitence, used as the Parson’s Tale, was probably the work of his old age. “Envoys” to his friends Scogan and Bukton, a translation of some balades by Sir Otes de Granson, and the Compleynt to his Purs complete the record of his minor poetry. We have his own statement that in his youth he had written many Balades, Roundels and Virelayes in honour of Love, and the two songs embedded respectively in the Parlement of Foules and the Prologue to the Legende of Good Women are charming and musical. His extant shorter poems, however, whether early or late, offer no excuse for claiming high rank for him as a lyrist. He had very little sheer singing power, and though there are fine lines in his short poems, witness the famous “Flee fro the prees and dwell with soothfastnesse,” they lack the sustained concentration of great work. From the drama, again, Chaucer was cut off, and it is idle to argue from the innumerable dramatic touches in his poems and his gift of characterization as to what he might have done had he lived two centuries later. His own age delighted in stories, and he gave it the stories it demanded invested with a humanity, a grace and strength which place him among the world’s greatest narrative poets, and which bring the England of his own day, with all the colour and warmth of life, wonderfully near to all his readers.

The part played by Chaucer in the development of the English language has often been overrated. He neither corrupted it, as used to be said, by introducing French words which Influence. it would otherwise have avoided, nor bore any such part in fixing it as was afterwards played by the translators of the Bible. When he was growing up educated society in England was still bilingual, and the changes in vocabulary and pronunciation which took place during his life were the natural results of a society, which had been bilingual with a bias towards French, giving an exclusive preference to English. The practical identity of Chaucer’s language with that of Gower shows that both merely used the best English of their day with the care and slightly conservative tendency which befitted poets. Chaucer’s service to the English language lies in his decisive success having made it impossible for any later English poet to attain fame, as Gower had done, by writing alternatively in Latin and French. The claim which should be made for him is 17 that, at least as regards poetry, he proved that English was “sufficient.”

Chaucer borrowed both his stanza forms and his “decasyllabic” couplets (mostly with an extra syllable at the end of the line) from Guillaume Machault, and his music, like that of his French master and his successors, depends very largely on assigning to every syllable its full value, and more especially on the due pronunciation of the final -e. The slower movement of change in Scotland allowed time for Chaucer to exercise a potent influence on Scottish poetry, but in England this final -e, to which most of the earlier grammatical forms by Chaucer’s time had been reduced, itself fell rapidly into disuse during the 15th century, and a serious barrier was thus raised to the appreciation of the artistic value of his verse. His disciples, Hoccleve and Lydgate, who at first had caught some echoes of his rhythms, gradually yielded to the change in pronunciation, so that there was no living tradition to hand down his secret, while successive copyists reduced his text to a state in which it was only by accident that lines could be scanned correctly. For fully three centuries his reputation was sustained solely by his narrative power, his warmest panegyrists betraying no consciousness that they were praising one of the greatest technical masters of poetry. Even when thus maimed, however, his works found readers and lovers in every generation, and every improvement in his text has set his fame on a surer basis.

CHAUDESAIGUES, a village of central France, in the department of Cantal, at the foot of the mountains of Aubrac, 19 m. S.S.W. of St Flour by road. Pop. (1906) town, 937; commune, 1558. It is celebrated for its hot mineral springs, which vary in temperature from 135° to 177° Fahr., and at their maximum rank as the hottest in France. The water, which contains bicarbonate of soda, is employed not only medicinally (for rheumatism, &c.), but also for the washing of fleeces, the incubation of eggs, and various other economic purposes; and it furnishes a ready means of heating the houses of the town during winter. In the immediate neighbourhood is the cold chalybeate spring of Condamine. The warm springs were known to the Romans, and are mentioned by Sidonius Apollinaris.

CHAUFFEUR (from Fr. chauffer), to heat, a term primarily used in French of a man in charge of a forge or furnace, and so of a stoker on a locomotive or in a steamship, but in its anglicized sense more particularly confined to a professional driver of a motor vehicle. (See also Brigandage.)

CHAULIEU, GUILLAUME AMFRYE DE (1639-1720), French poet and wit, was born at Fontenay, Normandy, in 1639. His father, maître des comptes of Rouen, sent him to study at the Collège de Navarre. Guillaume early showed the wit that was to distinguish him, and gained the favour of the duke of Vendôme, who procured for him the abbey of Aumale and other benefices. Louis Joseph, duke of Vendôme, and his brother Philippe, grand prior of the Knights of Malta in France, at that time had a joint establishment at the Temple, where they gathered round them a very gay and reckless circle. Chaulieu became the constant companion and adviser of the two princes. He made an expedition to Poland in the suite of the marquis de Béthune, hoping to make a career for himself in the court of John Sobieski; he saw one of the Polish king’s campaigns in Ukraine, but returned to Paris without securing any advancement. Saint-Simon says that the abbé helped his patron the grand prior to rob the duke of Vendôme, and that the king sent orders that the princes should take the management of their affairs from him. This account has been questioned by Sainte-Beuve, who regards Saint-Simon as a prejudiced witness. In his later years Chaulieu spent much time at the little court of the duchesse du Maine at Sceaux. There he became the trusted and devoted friend of Mdlle Delaunay, with whom he carried on an interesting correspondence. Among his poems the best known are “Fontenay” and “La Retraite.” Chaulieu died on the 27th of June 1720.

CHAUMETTE, PIERRE GASPARD (1763-1794), French revolutionist, was born at Nevers. Until the Revolution he lived a somewhat wandering life, interesting himself particularly in botany. He was a student of medicine at Paris in 1790, became one of the orators of the club of the Cordeliers, and contributed anonymously to the Révolutions de Paris. As member of the insurrectionary Commune of the 10th of August 1792, he was delegated to visit the prisons, with full power to arrest suspects. He was accused later of having taken part in the massacres of September, but was able to prove that at that time he had been sent by the provisional executive council to Normandy to oversee a requisition of 60,000 men. Returning 18 from this mission, he pronounced an eloquent discourse in favour of the republic. His simple manners, easy speech, ardent temperament and irreproachable private life gave him great influence in Paris, and he was elected president of the Commune, defending the municipality in that capacity at the bar of the Convention on the 31st of October 1792. Re-elected in the municipal elections of the 2nd of December 1792, he was soon charged with the functions of procurator of the Commune, and contributed with success to the enrolments of volunteers by his appeals to the populace. Chaumette was one of the ringleaders in the attacks of the 31st of May and of the 2nd of June 1793 on the Girondists, toward whom he showed himself relentless. He demanded the formation of a revolutionary army, and preached the extermination of all traitors. He was one of the promoters of the worship of Reason, and on the 10th of November 1793 he presented the goddess to the Convention in the guise of an actress. On the 23rd of the same month he obtained a decree closing all the churches of Paris, and placing the priests under strict surveillance; but on the 25th he retraced his steps and obtained from the Commune the free exercise of worship. He wished to save the Hébertists by a new insurrection and struggled against Robespierre; but a revolutionary decree promulgated by the Commune on his demand was overthrown by the Convention. Robespierre had him accused with the Hébertists; he was arrested, imprisoned in the Luxembourg, condemned by the Revolutionary tribunal and executed on the 13th of April 1794. Chaumette’s career had its brighter side. He was an ardent social reformer; he secured the abolition of corporal punishment in the schools, the suppression of lotteries, of houses of ill-fame and of obscene literature; he instituted reforms in the hospitals, and insisted on the honours of public burial for the poor.

CHAUMONT-EN-BASSIGNY, a town of eastern France, capital of the department of Haute-Marne, a railway junction 163 m. E.S.E. of Paris on the main line of the Eastern railway to Belfort. Pop. (1906) 12,089. Chaumont is picturesquely situated on an eminence between the rivers Marne and Suize in the angle formed by their confluence. To the west a lofty viaduct over the Suize carries the railway. The church of St-Jean-Baptiste dates from the 13th century, the choir and lateral chapels belonging to the 15th and 16th. In the interior the sculptured triforium (15th century), the spiral staircase in the transept and a Holy Sepulchre are of interest. The lycée and the hospital have chapels of the 17th and 16th centuries respectively. The Tour Hautefeuille (a keep of the 11th century) is the principal relic of a château of the counts of Champagne; the rest of the site is occupied by the law courts. In the Place de l’Escargot stands a statue of the chemist Philippe Lebon (1767-1804), born in Haute-Marne. Chaumont is the seat of a prefect and of a court of assizes, and has tribunals of first instance and of commerce, a lycée, training colleges, and a branch of the Bank of France. The main industries are glove-making and leather-dressing. The town has trade in grain, iron, mined in the vicinity, and leather. In 1190 it received a charter from the counts of Champagne. It was here that in 1814 Great Britain, Austria, Russia and Prussia concluded the treaty (dated March 1, signed March 9) by which they severally bound themselves not to conclude a separate peace with Napoleon, and to continue the war until France should have been reduced within the boundaries of 1792.

CHAUNCEY, ISAAC (1772-1840), American naval commander, was born at Black Rock, Connecticut, on the 20th of February 1772. He was brought up in the merchant service, and entered the United States navy as a lieutenant in 1798. His first services were rendered against the Barbary pirates. During these operations, more especially at Tripoli, he greatly distinguished himself, and was voted by Congress a sword of honour, which, however, does not appear to have been given him. The most active period of his life is that of his command on the Lakes during the War of 1812. He took the command at Sackett’s Harbor on Lake Ontario in October 1812. There was at that time only one American vessel, the brig “Oneida” (16), and one armed prize, a schooner, on the lake. But Commodore Chauncey brought from 400 to 500 officers and men with him, and local resources for building being abundant, he had by November formed a squadron of ten vessels, with which he attacked the Canadian port, York, taking it in April 1813, capturing one vessel and causing the destruction of another then building. He returned to Sackett’s Harbor. In May Sir James Lucas Yeo (1732-1818) came out from England with some 500 officers and men, to organize a squadron for service on the Lakes. By the end of the month he was ready for service with a squadron of eight ships and brigs, and some small craft. The governor, Sir G. Prevost, gave him no serious support. On the 29th of May, during Chauncey’s absence at Niagara, the Americans were attacked at Sackett’s Harbor and would have been defeated if Prevost had not insisted on a retreat at the very moment when the American shipbuilding yard was in danger of being burnt, with a ship of more than eight hundred tons on the stocks. The retreat of the British force gave Chauncey time to complete this vessel, the “General Pike,” which was so far superior to anything under Yeo’s command that she was said to be equal in effective strength to the whole of the British flotilla. The American commodore was considered by many of his subordinates to have displayed excessive caution. In August he skirmished with Sir James Yeo’s small squadron of six vessels, but made little effective use of his own fourteen. Two of his schooners were upset in a squall, with the loss of all hands, and he allowed two to be cut off by Yeo. Commodore Chauncey showed a preference for relying on his long guns, and a disinclination to come to close quarters. He was described as chasing the British squadron all round the lake, but his encounters did not go beyond artillery duels at long range, and he allowed his enemy to continue in existence long after he might have been destroyed. The winter suspended operations, and both sides made exertions to increase their forces. The Americans had the advantage of commanding greater resources for shipbuilding. Sir James Yeo began by blockading Sackett’s Harbor in the early part of 1814, but when the American squadron was ready he was compelled to retire by the disparity of the forces. The American commodore was now able to blockade the British flotilla at Kingston. When the cruising season of the lake was nearly over he in his turn retired to Sackett’s Harbor, and did not leave it for the rest of the war. During his later years he served as commissioner of the navy, and was president of the board of naval commissioners from 1833 till his death at Washington on the 27th of February 1840.

CHAUNCY, CHARLES (1592-1672), president of Harvard College, was born at Yardley-Bury, Hertfordshire, England, in November 1592, and was educated at Trinity College, Cambridge, of which he became a fellow. He was in turn vicar at Ware, Hertfordshire (1627-1633), and at Marston St Lawrence, Northamptonshire (1633-1637). Refusing to observe the ecclesiastical regulations of Archbishop Laud, he was brought before the court of high commission in 1629, and again in 1634, when, for opposing the placing of a rail around the communion table, he was suspended and imprisoned. His formal recantation in February 1637 caused him lasting self-reproach and humiliation. In 1637 he emigrated to America, and from 1638 until 1641 was an associate pastor at Plymouth, where, however, his advocacy of the baptism of infants by immersion caused dissatisfaction. He was the pastor at Scituate, Massachusetts, from 1641 until 1654, and from 1654 until his death was president of Harvard College, as the successor of the first president Henry Dunster (c. 1612-1659). He died on the 19th of February 1672. By his sermons and his writings he exerted a great influence in colonial Massachusetts, and according to Mather was “a most incomparable scholar.” His writings include: The Plain Doctrine of the Justification of a Sinner in the Sight of God (1659) and Antisynodalia Scripta Americana (1662). His son, Isaac 19 Chauncy (1632-1712), who removed to England, was a voluminous writer on theological subjects.

President Chauncy’s great-grandson, CHARLES CHAUNCY (1705-1787), a prominent American theologian, was born in Boston, Massachusetts, on the 1st of January 1705, and graduated at Harvard in 1721. In 1727 he was chosen as the colleague of Thomas Foxcroft (1697-1769) in the pastorate of the First Church of Boston, continuing as pastor of this church until his death. At the time of the “Great Awakening” of 1740-1743 and afterwards, Chauncy was the leader of the so-called “Old Light” party in New England, which strongly condemned the Whitefieldian revival as an outbreak of emotional extravagance. His views were ably presented in his sermon Enthusiasm and in his Seasonable Thoughts on the State of Religion in New England (1743), written in answer to Jonathan Edwards’s Some Thoughts Concerning the Present Revival of Religion in New England (1742). He also took a leading part in opposition to the projected establishment of an Anglican Episcopate in America, and before and during the American War of Independence he ardently supported the whig or patriot party. Theologically he has been classed as a precursor of the New England Unitarians. He died in Boston on the 10th of February 1787. His publications include: Compleat View of Episcopacy, as Exhibited in the Fathers of the Christian Church, until the close of the Second Century (1771); Salvation of All Men, Illustrated and Vindicated as a Scripture Doctrine (1782); The Mystery Hid from Ages and Generations made manifest by the Gospel-Revelation (1783); and Five Dissertations on the Fall and its Consequences (1785).

CHAUNY, a town of northern France in the department of Aisne, 19 m. S. by W. of St Quentin by rail. Pop. (1906) 10,127. The town is situated on the Oise (which here becomes navigable) and at the junction of the canal of St Quentin with the lateral canal of the Oise, and carries on an active trade. It contains mirror-polishing works, subsidiary to the mirror-works of St Gobain, chemical works, sugar manufactories, metal foundries and breweries. Chauny was the scene of much fighting in the Hundred Years’ War.

CHAUTAUQUA, a village on the west shore of Chautauqua Lake in the town of Chautauqua, Chautauqua county, New York, U.S.A. Pop. of the town (1900), 3590; (1905) 3505; (1910) 3515; of the village (1908) about 750. The lake is a beautiful body of water over 1300 ft. above sea-level, 20 m. long, and from a few hundred yards to 3 m. in width. The town of Chautauqua is situated near the north end and is within easy reach by steamboat and electric car connexions with the main railways between the east and the west. The town is known almost solely as being the permanent home of the Chautauqua Institution, a system of popular education founded in 1874 by Lewis Miller (1829-1899) of Akron, Ohio, and Bishop John H. Vincent (b. 1832). The village, covering about three hundred acres of land, is carefully laid out to provide for the work of the Institution.

The Chautauqua Institution began as a Sunday-School Normal Institute, and for nearly a quarter of a century the administration was in the hands of Mr Miller, who was responsible for the business management, and Bishop Vincent, who was head of the instruction department. Though founded by Methodists, in its earliest years it became non-sectarian and has furnished a meeting-ground for members of all sects and denominations. At the very outset the activities of the assembly were twofold: (1) the conducting of a summer school for Sunday-school teachers, and (2) the presentation of a series of correlated lectures and entertainments. Although the movement was and still is primarily religious, it has always been assumed that the best religious education must necessarily take advantage of the best that the educational world can afford in the literatures, arts and sciences. The scope of the plan rapidly broadened, and in 1879 a regular group of schools with graded courses of study was established. At about the same time, also, the Chautauqua Literary and Scientific Circle, providing a continuous home-reading system, was founded. The season lasts during June, July and August. In 1907 some 325 lectures, concerts, readings and entertainments were presented by a group of over 190 lecturers, readers and musicians, while at the same time 200 courses in the summer schools were offered by a faculty of instructors drawn from the leading colleges and normal schools of the country.

The Chautauqua movement has had an immense influence on education in the United States, an influence which is especially marked in three directions: (1) in the establishment of about 300 local assemblies or “Chautauquas” in the United States patterned after the mother Chautauqua; (2) in the promotion of the idea of summer education, which has been followed by the founding of summer schools or sessions at a large number of American universities, and of various special summer schools, such as the Catholic Summer School of America, with headquarters at Cliff Haven, Clinton county, New York, and the Jewish Chautauqua Society, with headquarters at Buffalo, N.Y.; and (3) in the establishment of numerous correspondence schools patterned in a general way after the system provided by the Chautauqua Literary and Scientific Circle.

CHAUVELIN, BERNARD FRANÇOIS, Marquis de (1766-1832), French diplomatist and administrator. Though master of the king’s wardrobe in 1789, he joined in the Revolution. He served in the army of Flanders, and then was sent to London in February 1792, to induce England to remain neutral in the war which was about to break out between France and “the king of Bohemia and Hungary.” He was well received at first, but after the 10th of August 1792 he was no longer officially recognized at court, and on the execution of Louis XVI. (21st of January 1793) he was given eight days to leave England. After an unsuccessful embassy in Tuscany, he was imprisoned as a suspect during the Terror, but freed after the 9th Thermidor. Under Napoleon he became a member of the council of state, and from 1812 to 1814 he governed Catalonia under the title of intendant-general, being charged to win over the Catalonians to King Joseph Bonaparte. He remained in private life during the Restoration and the Hundred Days. In 1816 he was elected deputy, and spoke in favour of liberty of the press and extension of the franchise. Though he was again deputy in 1827 he played no part in public affairs, and resigned in 1829.

CHAUVIGNY, a town of western France, in the department of Vienne, 20 m. E. of Poitiers by rail. Pop. (1906) 2326. The town is finely situated overlooking the Vienne and a small torrent, and has two interesting Romanesque churches, both restored in modern times. There are also ruins of a château of the bishops of Poitiers, and of other strongholds. Near Chauvigny is the curious bone-cavern of Jioux, the entrance to which is fortified by large blocks of stone. The town carries on lime-burning and plaster-manufacture, and there are stone quarries in the vicinity. Trade is in wool and feathers.

CHAUVIN, ÉTIENNE (1640-1725), French Protestant divine, was born at Nîmes on the 18th of April 1640. At the revocation of the Edict of Nantes he retired to Rotterdam, where he was for some years preacher at the Walloon church; in 1695 the elector of Brandenburg appointed him pastor and professor of philosophy, and later inspector of the French college at Berlin, where he enjoyed considerable reputation as a representative of Cartesianism and as a student of physics. His principal work is a laborious Lexicon Rationale, sive Thesaurus Philosophicus (Rotterdam, 1692; new and enlarged edition, Leuwarden, 1713). 20 He also wrote Theses de Cognitione Dei (1662), and started the Nouveau Journal des Savans (1694-1698).

CHAUVINISM, a term for unreasonable and exaggerated patriotism, the French equivalent of “Jingoism.” The word originally signified idolatry of Napoleon, being taken from a much-wounded veteran, Nicholas Chauvin, who, by his adoration of the emperor, became the type of blind enthusiasm for national military glory.

CHAUX DE FONDS, LA, a large industrial town in the Swiss canton of Neuchâtel. It is about 19 m. by rail N. W. of Neuchâtel, and stands at a height of about 3255 ft. in a valley (5 m. long) of the same name in the Jura. Pop. (1900) 35,968 (only 13,659 in 1850); (1905) 38,700, mainly French-speaking and Protestants; of the 6114 “Catholics” the majority are “Old Catholics.” It is a centre of the watch-making industry, especially of gold watch cases; about 70% of those manufactured in Switzerland are turned out here. In 1900 it exported watches to the value of nearly £3,000,000 sterling. There is a school of industrial art (engraving and enamelling watch cases) and a school of watch-making (including instruction in the manufacture of chronometers and other scientific instruments of precision). It boasts of being le plus gros village de l’Europe, and certainly has preserved some of the features of a big village. Léopold Robert (1794-1835), the painter, was born here.

CHAVES, a town of northern Portugal, in the district of Villa Real, formerly included in the province of Traz os Montes; 8 m. S. of the Spanish frontier, on the right bank of the river Tamega. Pop. (1900) 6388. Chaves is the ancient Aquae Flaviae, famous for its hot saline springs, which are still in use. A fine Roman bridge of 18 arches spans the Tamega. In the 16th century Chaves contained 20,000 inhabitants; it was long one of the principal frontier fortresses, and in fact derives its present name from the position which makes it the “keys,” or chaves, of the north. One of its churches contains the tomb of Alphonso I. of Portugal (1139-1185). In 1830 the town gave the title of marquess to Pinto da Fonseca, a leader of the Miguelite party.

CHAZELLES, JEAN MATHIEU DE (1657-1710), French hydrographer, was born at Lyons on the 24th of July 1657. He was nominated professor of hydrography at Marseilles in 1685, and in that capacity carried out various coast surveys. In 1693 he was engaged to publish a second volume of the Neptune français, which was to include the hydrography of the Mediterranean. For this purpose he visited the Levant and Egypt. When in Egypt he measured the pyramids, and, finding that the angles formed by the sides of the largest were in the direction of the four cardinal points, he concluded that this position must have been intended, and also that the poles of the earth and meridians had not deviated since the erection of those structures. He was made a member of the Academy in 1695, and died in Paris on the 16th of January 1710.

CHEADLE, a town in the Altrincham parliamentary division of Cheshire, England, 6 m. S. of Manchester, included in the urban district of Cheadle and Gatley. Pop. (1901) 7916. This is one of the numerous townships of modern growth which fringe the southern boundaries of Manchester, and practically form suburbs of that city. Stockport lies immediately to the east. The name occurs in the formerly separate villages of Cheadle Hulme, Cheadle Bulkeley and Cheadle Moseley. There are cotton printing and bleaching works in the locality. The parish church of St Giles, Cheadle, is Perpendicular, containing an altar-tomb of the 15th century for two knights.

CHEADLE, a market town in the Leek parliamentary division of Staffordshire, England, 13 m. N.E. of Stafford, and the terminus of a branch line from Cresswell on the North Staffordshire railway. Pop. (1901) 5186. The Roman Catholic church of St Giles, with a lofty spire, was designed by Pugin and erected in 1846. The interior is lavishly decorated. There are considerable collieries in the neighbourhood, and silk and tape works in the town. In the neighbouring Froghall district limestone is quarried, and there are manufactures of copper. In Cheadle two fairs of ancient origin are held annually.

CHEATING, “the fraudulently obtaining the property of another by any deceitful practice not amounting to felony, which practice is of such a nature that it directly affects, or may directly affect, the public at large” (Stephen, Digest of Criminal Law, chap. xl. §367). Cheating is either a common law or statutory offence, and is punishable as a misdemeanour. An indictment for cheating at common law is of comparatively rare occurrence, and the statutory crime usually presents itself in the form of obtaining money by false pretences (q.v.). The word “cheat” is a variant of “escheat,” i.e. the reversion of land to a lord of the fee through the failure of blood of the tenant. The shortened form “cheater” for “escheator” is found early in the legal sense, and chetynge appears in the Promptorium Parvulorum, c. 1440, as the equivalent of confiscatio. In the 16th century “cheat” occurs in vocabularies of thieves and other slang, and in such works as the Use of Dice-Play (1532). It is frequent in Thomas Harman’s Caveat or Warening for ... Vagabones (1567), in the sense of “thing,” with a descriptive word attached, e.g. smeling chete = nose. In the tract Mihil Mumchance, his Discoverie of the Art of Cheating, doubtfully attributed to Robert Greene (1560-1592), we find that gamesters call themselves cheaters, “borrowing the term from the lawyers.” The sense development is obscure, but it would seem to be due to the extortionate or fraudulent demands made by legal “escheators.”

CHEBICHEV, PAFNUTIY LVOVICH (1821-1894), Russian mathematician, was born at Borovsk on the 26th of May 1821. He was educated at the university of Moscow, and in 1859 became professor of mathematics in the university of St Petersburg, a position from which he retired in 1880. He was chosen a correspondent of the Institute of France in 1860, and succeeded to the high honour of associé étranger in 1874. He was also a foreign member of the Royal Society of London. After N.I. Lobachevskiy he probably ranks as the most distinguished mathematician Russia has produced. In 1841 he published a valuable paper, “Sur la convergence de la serié de Taylor,” in Crelle’s Journal. His best-known papers, however, deal with prime numbers; in one of these (“Sur les nombres premiers,” 1850) he established the existence of limits within which must be comprised the sum of the logarithms of the primes inferior to a given number. Another question to which he devoted much attention was that of obtaining rectilinear motion by linkage. The parallel motion known by his name is a three-bar linkage, which gives a very close approximation to exact rectilinear motion, but in spite of all his efforts he failed to devise one that produced absolutely true rectilinear motion. At last, indeed, he came to the conclusion that to do so was impossible, and in that conviction set to work to find a rigorous proof of the impossibility. While he was engaged on this task the desired linkage, which moved the highest admiration of J.J. Sylvester, was discovered and exhibited to him by one of his pupils, named Lipkin, who, however, it was afterwards found, had been anticipated by A. Peaucellier. Chebichev further constructed an instrument for drawing large circles, and an arithmetical machine with continuous motion. His mathematical writings, which account for some forty entries in the Royal Society’s catalogue of scientific papers, cover a wide range of subjects, such as the theory of probabilities, quadratic forms, theory of integrals, gearings, the construction of geographical maps, &c. He also published a Traité de la théorie des nombres. He died at St Petersburg on the 8th of December 1894.

CHEBOYGAN, a city and the county-seat of Cheboygan county, Michigan, U.S.A., on South Channel (between Lakes Michigan and Huron), at the mouth of Cheboygan river, in the N. part of the lower peninsula. Pop. (1890) 6235; (1900) 6489, of whom 2101 were foreign-born; (1904) 6730; (1910) 6859. It is served by the Michigan Central and the Detroit & Mackinac railways, and by steamboat lines to Chicago, Milwaukee, Detroit, Sault Ste Marie, Green Bay and other lake ports; and is connected by ferry with Mackinac and Pointe aux Pins. During a great part of the year small boats ply between Cheboygan and the head of Crooked Lake, over the “Inland Route.” Cheboygan is situated in a fertile farming region, for 21 which it is a trade centre, and it has lumber mills, tanneries, paper mills, boiler works, and other manufacturing establishments. The water-works are owned and operated by the municipality. The city, at first called Duncan, then Inverness, and finally Cheboygan, was settled in 1846, incorporated as a village in 1871, reincorporated in 1877, and chartered as a city in 1889.

CHECHENZES, Tchetchen, or Khists (Kisti), the last being the name by which they are known to the Georgians, a people of the eastern Caucasus occupying the whole of west Daghestan. They call themselves Nakhtche, “people.” A wild, fierce people, they fought desperately against Russian aggression in the 18th century under Daûd Beg and Oman Khan and Shamyl, and in the 19th under Khazi-Mollah, and even now some are independent in the mountain districts. On the surrender of the chieftain Shamyl to Russia in 1859 numbers of them migrated into Armenia. In physique the Chechenzes resemble the Circassians, and have the same haughtiness of carriage. They are of a generous temperament, very hospitable, but quick to revenge. They are fond of fine clothes, the women wearing rich robes with wide, pink silk trousers, silver bracelets and yellow sandals. Their houses, however, are mere hovels, some dug out of the ground, others formed of boughs and stones. Before their subjection to Russia they were remarkable for their independence of spirit and love of freedom. Everybody was equal, and they had no slaves except prisoners of war. Government in each commune was by popular assembly, and the administration of justice was in the hands of the wronged. Murder and robbery with violence could be expiated only by death, unless the criminal allowed his hair to grow and the injured man consented to shave it himself and take an oath of brotherhood on the Koran. Otherwise the law of vendetta was fully carried out with curious details. The wronged man, wrapped in a white woollen shroud, and carrying a coin to serve as payment to a priest for saying the prayers for the dead, started out in search of his enemy. When the offender was found he must fight to a finish. A remarkable custom among one tribe is that if a betrothed man or woman dies on the eve of her wedding, the marriage ceremony is still performed, the dead being formally united to the living before witnesses, the father, in case it is the girl who dies, never failing to pay her dowry. The religion of the Chechenzes is Mahommedanism, mixed, however, with Christian doctrines and observances. Three churches near Kistin in honour of St George and the Virgin are visited as places of pilgrimage, and rams are there offered as sacrifices. The Chechenzes number upwards of 200,000. They speak a distinct language, of which there are said to be twenty separate dialects.

CHECKERS, the name by which the game of draughts (q.v.) is known in America. The origin of the name is the same as that of “chess” (q.v.).

CHEDDAR, a small town in the Wells parliamentary division of Somersetshire, England, 22 m. S.W. of Bristol by a branch of the Great Western railway. Pop. (1901) 1975. The town, with its Perpendicular church and its picturesque market-cross, lies below the south-western face of the Mendip Hills, which rise sharply from 600 to 800 ft. To the west stretches the valley of the river Axe, broad, low and flat. A fine gorge opening from the hills immediately upon the site of the town is known as Cheddar cliffs from the sheer walls which flank it; the contrast of its rocks and rich vegetation, and the falls of a small stream traversing it, make up a beautiful scene admired by many visitors. Several stalactitical caverns are also seen, and prehistoric British and Roman relics discovered in and near them are preserved in a small museum. The two caverns most frequently visited are called respectively Cox’s and Gough’s; in each, but especially in the first, there is a remarkable collection of fantastic and beautiful stalactitical forms. There are other caverns of greater extent but less beauty, but their extent is not completely explored. The remains discovered in the caves give evidence of British and Roman settlements at Cheddar (Cedre, Chedare), which was a convenient trade centre. The manor of Cheddar was a royal demesne in Saxon times, and the witenagemot was held there in 966 and 968. It was granted by John in 1204 to Hugh, archdeacon of Wells, who sold it to the bishop of Bath and Wells in 1229, whose successors were overlords until 1553, when the bishop granted it to the king. It is now owned by the marquis of Bath. By a charter of 1231 extensive liberties in the manor of Cheddar were granted to Bishop Joceline, who by a charter of 1235 obtained the right to hold a weekly market and fair. By a charter of Edward III. (1337) Cheddar was removed from the king’s forest of Mendip. The market was discontinued about 1690. Fairs are now held on the 4th of May and the 29th of October under the original grants. The name of Cheddar is given to a well-known species of cheese (see Dairy), the manufacture of which began in the 17th century in the town and neighbourhood.

CHEDUBA, or Man-aung, an island in the Bay of Bengal, situated 10 m. from the coast of Arakan, between 18° 40′ and 18° 56′ N. lat., and between 93° 31′ and 93° 50′ E. long. It forms part of the Kyaukpyu district of Arakan. It extends about 20 m. in length from N. to S., and 17 m. from E. to W., and its area of 220 sq. m. supports a population of 26,899 (in 1901). The channel between the island and the mainland is navigable for boats, but not for large vessels. The surface of the interior is richly diversified by hill and dale, and in the southern portion some of the heights exceed a thousand feet in elevation. There are various indications of former volcanic activity, and along the coast are earthy cones covered with green-sward, from which issue springs of muddy water emitting bubbles of gas. Copper, iron and silver ore have been discovered; but the island is chiefly noted for its petroleum wells, the oil derived from which is of excellent quality, and is extensively used in the composition of paint, as it preserves wood from the ravages of insects. Timber is not abundant, but the gamboge tree and the wood-oil tree are found of a good size. Tobacco, cotton, sugar-cane, hemp and indigo are grown, and the staple article is rice, which is of superior quality, and the chief article of export. The inhabitants of the island are mainly Maghs. Cheduba fell to the Burmese in the latter part of the 18th century. From them it was captured in 1824 by the British, whose possession of it was confirmed in 1826 by the treaty concluded with the Burmese at Yandaboo.

CHEERING, the uttering or making of sounds encouraging, stimulating or exciting to action, indicating approval of acclaiming or welcoming persons, announcements of events and the like. The word “cheer” meant originally face, countenance, expression, and came through the O. Fr. into Mid. Eng. in the 13th century from the Low Lat. cara, head; this is generally referred to the Gr. κάρα. Cara is used by the 6th-century poet Flavius Cresconius Corippus, “Postquam venere verendam Caesaris ante caram” (In Laudem Justini Minoris). “Cheer” was at first qualified with epithets, both of joy and gladness and of sorrow; compare “She thanked Dyomede for alle ... his gode chere” (Chaucer, Troylus) with “If they sing ... ’tis with so dull a cheere” (Shakespeare, Sonnets, xcvii.). An early transference in meaning was to hospitality or entertainment, and hence to food and drink, “good cheer.” The sense of a shout of encouragement or applause is a late use. Defoe (Captain Singleton) speaks of it as a sailor’s word, and the meaning does not appear in Johnson. Of the different words or rather sounds that are used in cheering, “hurrah,” though now generally looked on as the typical British form of cheer, is found in various forms in German, Scandinavian, Russian (urá), French (houra). It is probably onomatopoeic in origin; some connect it with such words as “hurry,” “whirl”; the meaning would then be “haste,” to encourage speed or onset in battle. The English “hurrah” was preceded by “huzza,” stated to be a sailor’s word, and generally connected with “heeze,” to hoist, probably being one of the cries that sailors use when hauling or hoisting. The German hoch, seen in full in hoch lebe der Kaiser, &c., the French vive, Italian and Spanish viva, evviva, are cries rather 22 of acclamation than encouragement. The Japanese shout banzai became familiar during the Russo-Japanese War. In reports of parliamentary and other debates the insertion of “cheers” at any point in a speech indicates that approval was shown by members of the House by emphatic utterances of “hear hear.” Cheering may be tumultuous, or it may be conducted rhythmically by prearrangement, as in the case of the “Hip-hip-hip” by way of introduction to a simultaneous “hurrah.”

Rhythmical cheering has been developed to its greatest extent in America in the college yells, which may be regarded as a development of the primitive war-cry; this custom has no real analogue at English schools and universities, but the New Zealand football team in 1907 familiarized English crowds at their matches with a similar sort of war-cry adopted from the Maoris. In American schools and colleges there is usually one cheer for the institution as a whole and others for the different classes. The oldest and simplest are those of the New England colleges. The original yells of Harvard and Yale are identical in form, being composed of rah (abbreviation of hurrah) nine times repeated, shouted in unison with the name of the university at the end. The Yale cheer is given faster than that of Harvard. Many institutions have several different yells, a favourite variation being the name of the college shouted nine times in a slow and prolonged manner. The best known of these variants is the Yale cheer, partly taken from the Frogs of Aristophanes, which runs thus:

The regular cheer of Princeton is:

This is expanded into the “triple cheer”:

The “railroad cheer” is like the foregoing, but begun very slowly and broadly, and gradually accelerated to the end, which is enunciated as fast as possible. Many cheers are formed like that of Toronto University:

Another variety of yell is illustrated by that of the School of Practical Science of Toronto University:

The cheer of the United States Naval Academy is an imitation of a nautical syren. The Amherst cheer is:

Besides the cheers of individual institutions there are some common to all, generally used to compliment some successful athlete or popular professor. One of the oldest examples of these personal cheers is:

followed by a stamping on the floor in the same rhythm.

College yells are used particularly at athletic contests. In any large college there are several leaders, chosen by the students, who stand in front and call for the different songs and cheers, directing with their arms in the fashion of an orchestral conductor. This cheering and singing form one of the distinctive features of inter-collegiate and scholastic athletic contests in America.

CHEESE (Lat. caseus), a solidified preparation from milk, the essential constituent of which is the proteinous or nitrogenous substance casein. All cheese contains in addition some proportion of fatty matter or butter, and in the more valuable varieties the butter present is often greater in amount than the casein. Cheese being thus a compound substance of no definite composition is found in commerce of many different varieties and qualities; and such qualities are generally recognized by the names of the localities in which they are manufactured. The principal distinctions arise from differences in the composition and condition of the milk operated upon, from variations in the method of preparation and curing, and from the use of the milk of other animals besides the cow, as, for example, the goat and the ewe, from the milk of both of which cheese is manufactured on a commercial scale. For details about different cheeses and cheese-making, see Dairy. From the Urdu chiz (“thing”) comes the slang expression “the cheese,” meaning “the perfect thing,” apparently from Anglo-Indian usage.

CHEESE CLOTH, the name given to cloth, usually made from flax or tow yarns, of an open character, resembling a fine riddle or sieve, used for wrapping cheese. A finer quality and texture is made for women’s gowns. A similar cloth is used for inside linings in the upholstery trade, and for the ground of embroidery.

CHEETA (Chita), or Hunting-Leopard (Cynaelurus jubatus, formerly known as Gueparda jubata), a member of the family Felidae, distinguished by its claws being only partially retractile (see Carnivora). The cheeta attains a length of 3 to 4 ft.; it is of a pale fulvous colour, marked with numerous spots of black on the upper surface and sides, and is nearly white beneath. The fur is somewhat crisp, altogether lacking the sleekness which characterizes the fur of the typical cats, and the tail is long and somewhat bushy at the extremity. In confinement the cheeta soon becomes fond of those who are kind to it, and gives evidence of its attachment in an open, dog-like manner. The cheeta is found throughout Africa and southern Asia, and has been employed for centuries in India and Persia in hunting antelopes and other game. According to Sir W. Jones, this mode of hunting originated with Hushing, king of Persia, 865 B.C., and afterwards became so popular that certain of the Mongol emperors were in the habit of being accompanied in their sporting expeditions by a thousand hunting leopards. In prosecuting this sport at the present day the cheeta is conveyed to the field in a low car without sides, hooded and chained like hunting-birds in Europe in the days of falconry. When a herd of deer or antelopes is seen, the car, which bears a close resemblance to the ordinary vehicles used by the peasants, is usually brought within 200 yds. of the game before the latter takes alarm; the cheeta is then let loose and the hood removed from its eyes. No sooner does it see the herd, than dropping from the car on the side remote from its prey, it approaches stealthily, making use of whatever means of concealment the nature of the ground permits, until observed, when making a few gigantic bounds, it generally arrives in the midst of the herd and brings down its victim with a stroke of its paw. The sportsman then approaches, draws off a bowl of the victim’s blood, and puts it before the cheeta, which is again hooded and led back to the car. Should it not succeed in reaching the herd in the first few bounds, it makes no further effort to pursue, but retires seemingly dispirited to the car. In Africa the cheeta is only valued for its skin, which is worn by chiefs and other people of rank. It should be added that in India the name cheeta (chita) is applied also to the leopard.

CHEFFONIER, properly Chiffonier, a piece of furniture differentiated from the sideboard by its smaller size and by the 23 enclosure of the whole of the front by doors. Its name (which comes from the French for a rag-gatherer) suggests that it was originally intended as a receptacle for odds and ends which had no place elsewhere, but it now usually serves the purpose of a sideboard. It is a remote and illegitimate descendant of the cabinet; it has rarely been elegant and never beautiful. It was one of the many curious developments of the mixed taste, at once cumbrous and bizarre, which prevailed in furniture during the Empire period in England. The earliest cheffoniers date from that time; they are usually of rosewood—the favourite timber of that moment; their “furniture” (the technical name for knobs, handles and escutcheons) was most commonly of brass, and there was very often a raised shelf with a pierced brass gallery at the back. The doors were well panelled and often edged with brass-beading, while the feet were pads or claws, or, in the choicer examples, sphinxes in gilded bronze. Cheffoniers are still made in England in cheap forms and in great number.

CHEH-KIANG, an eastern province of China, bounded N. by the province of Kiang-su, E. by the sea, S. by the province of Fu-kien, and W. by the provinces of Kiang-si and Ngan-hui. It occupies an area of about 36,000 sq. m., and contains a population of 11,800,000. With the exception of a small portion of the great delta plain, which extends across the frontier from the province of Kiang-su, and in which are situated the famous cities of Hu Chow, Ka-hing, Hang-chow, Shao-Sing and Ning-po, the province forms a portion of the Nan-shan of south-eastern China, and is hilly throughout. The Nan-shan ranges run through the centre of the province from south-west to north-east, and divide it into a northern portion, the greater part of which is drained by the Tsien-t’ang-kiang, and a southern portion which is chiefly occupied by the Ta-chi basin. The valleys enclosed between the mountain ranges are numerous, fertile, and for the most part of exquisite beauty. The hilly portion of the province furnishes large supplies of tea, and in the plain which extends along the coast, north of Ning-po, a great quantity of silk is produced. In minerals the province is poor. Coal and iron are occasionally met with, and traces of copper ore are to be found in places, but none of these minerals exists in sufficiently large deposits to make mining remunerative. The province, however, produces cotton, rice, ground-nuts, wheat, indigo, tallow and beans in abundance. The principal cities are Hang-chow, which is famed for the beauty of its surroundings, Ning-po, which has been frequented by foreign ships ever since the Portuguese visited it in the 16th century, and Wênchow. Opposite Ning-po, at a distance of about 50 m., lies the island of Chusan, the largest of a group bearing that general name. This island is 21 m. long, and about 50 m. in circumference. It is very mountainous, and is surrounded by numerous islands and islets. On its south side stands the walled town of Ting-hai, in front of which is the principal harbour. The population is returned as 50,000.

CHEKE, SIR JOHN (1514-1557), English classical scholar, was the son of Peter Cheke, esquire-bedell of Cambridge University. He was educated at St John’s College, Cambridge, where he became a fellow in 1529. While there he adopted the principles of the Reformation. His learning gained him an exhibition from the king, and in 1540, on Henry VIII.’s foundation of the regius professorships, he was elected to the chair of Greek. Amongst his pupils at St John’s were Lord Burghley, who married Cheke’s sister Mary, and Roger Ascham, who in The Schoolmaster gives Cheke the highest praise for scholarship and character. Together with Sir Thomas Smith, he introduced a new method of Greek pronunciation very similar to that commonly used in England in the 19th century. It was strenuously opposed in the University, where the continental method prevailed, and Bishop Gardiner, as chancellor, issued a decree against it (June 1542); but Cheke ultimately triumphed. On the 10th of July 1554, he was chosen as tutor to Prince Edward, and after his pupil’s accession to the throne he continued his instructions. Cheke took a fairly active share in public life; he sat, as member for Bletchingley, for the parliaments of 1547 and 1552-1553; he was made provost of King’s College, Cambridge (April 1, 1548), was one of the commissioners for visiting that university as well as Oxford and Eton, and was appointed with seven divines to draw up a body of laws for the governance of the church. On the 11th of October 1551 he was knighted; in 1553 he was made one of the secretaries of state, and sworn of the privy council. His zeal for Protestantism induced him to follow the duke of Northumberland, and he filled the office of secretary of state for Lady Jane Grey during her nine days’ reign. In consequence Mary threw him into the Tower (July 27, 1553), and confiscated his wealth. He was, however, released on the 13th of September 1554, and granted permission to travel abroad. He went first to Basel, then visited Italy, giving lectures in Greek at Padua, and finally settled at Strassburg, teaching Greek for his living. In the spring of 1556 he visited Brussels to see his wife; on his way back, between Brussels and Antwerp, he and Sir Peter Carew were treacherously seized (May 15) by order of Philip of Spain, hurried over to England, and imprisoned in the Tower. Cheke was visited by two priests and by Dr John Feckenham, dean of St Paul’s, whom he had formerly tried to convert to Protestantism, and, terrified by a threat of the stake, he gave way and was received into the Church of Rome by Cardinal Pole, being cruelly forced to make two public recantations. Overcome with shame, he did not long survive, but died in London on the 13th of September 1557, carrying, as T. Fuller says (Church History), “God’s pardon and all good men’s pity along with him.” About 1547 Cheke married Mary, daughter of Richard Hill, sergeant of the wine-cellar to Henry VIII., and by her he had three sons. The descendants of one of these, Henry, known only for his translation of an Italian morality play Freewyl (Tragedio del Libero Arbitrio) by Nigri de Bassano, settled at Pyrgo in Essex.

CHELLIAN, the name given by the French anthropologist G. de Mortillet to the first epoch of the Quaternary period when the earliest human remains are discoverable. The word is derived from the French town Chelles in the department of Seine-et-Marne. The climate of the Chellian epoch was warm and humid as evidenced by the wild growth of fig-trees and laurels. The animals characteristic of the epoch are the Elephas antiquus, the rhinoceros, the cave-bear, the hippopotamus and the striped hyaena. Man existed and belonged to the Neanderthal type. The implements characteristic of the period are flints chipped into leaf-shaped forms and held in the hand when used. The drift-beds of St Acheul (Amiens), of Menchecourt (Abbeville), of Hoxne (Suffolk), and the detrital laterite of Madras are considered by de Mortillet to be synchronous with the Chellian beds.

CHELMSFORD, FREDERIC THESIGER, 1st Baron (1794-1878), lord chancellor of England, was the third son of Charles Thesiger, and was born in London on the 15th of April 1794. His father, collector of customs at St Vincent’s, was the son of a Saxon gentleman who had migrated to England and become secretary to Lord Rockingham, and was the brother of Sir Frederic Thesiger, naval A.D.C. to Nelson at Copenhagen. Young Frederic Thesiger was originally destined for a naval 24 career, and he served as a midshipman on board the “Cambrian” frigate in 1807 at the second bombardment of Copenhagen. His only surviving brother, however, died about this time, and he became entitled to succeed to a valuable estate in the West Indies, so it was decided that he should leave the navy and study law, with a view to practising in the West Indies and eventually managing his property in person. Another change of fortune, however, awaited him, for a volcano destroyed the family estate, and he was thrown back upon his prospect of a legal practice in the West Indies. He proceeded to enter at Gray’s Inn in 1813, and was called on the 18th of November 1818, another change in his prospects being brought about by the strong advice of Godfrey Sykes, a special pleader in whose chambers he had been a pupil, that he should remain to try his fortune in England. He accordingly joined the home circuit, and soon got into good practice at the Surrey sessions, while he also made a fortunate purchase in buying the right to appear in the old palace court (see Lord Steward). In 1824 he distinguished himself by his defence of Joseph Hunt when on his trial at Hertford with John Thurtell for the murder of Wm. Weare; and eight years later at Chelmsford assizes he won a hard-fought action in an ejectment case after three trials, to which he attributed so much of his subsequent success that when he was raised to the peerage he assumed the title Lord Chelmsford. In 1834 he was made king’s counsel, and in 1835 was briefed in the Dublin election inquiry which unseated Daniel O’Connell. In 1840 he was elected M.P. for Woodstock. In 1844 he became solicitor-general, but having ceased to enjoy the favour of the duke of Marlborough, lost his seat for Woodstock and had to find another at Abingdon. In 1845 he became attorney-general, holding the post until the fall of the Peel administration on the 3rd of July 1846. Thus by three days Thesiger missed being chief justice of the common pleas, for on the 6th of July Sir Nicholas Tindal died, and the seat on the bench, which would have been Thesiger’s as of right, fell to the Liberal attorney-general, Sir Thomas Wilde. Sir Frederic Thesiger remained in parliament, changing his seat, however, again in 1852, and becoming member for Stamford. During this period he enjoyed a very large practice at the bar, being employed in many causes célèbres. On Lord Derby coming into office for the second time in 1858, Sir Frederic Thesiger was raised straight from the bar to the lord chancellorship (as were Lord Brougham, Lord Selborne and Lord Halsbury). In the following year Lord Derby resigned and his cabinet was broken up. Again in 1866, on Lord Derby coming into office for the third time, Lord Chelmsford became lord chancellor for a short period. In 1868 Lord Derby retired, and Disraeli, who took his place as prime minister, wished for Lord Cairns as lord chancellor. Lord Chelmsford was very sore at his supersession and the manner of it, but, according to Lord Malmesbury he retired under a compact made before he took office. Ten years later Lord Chelmsford died in London on the 5th of October 1878. Lord Chelmsford had married in 1822 Anna Maria Tinling. He left four sons and three daughters, of whom the eldest, Frederick Augustus, 2nd Baron Chelmsford (1827-1905), earned distinction as a soldier, while the third, Alfred Henry Thesiger (1838-1880) was made a lord justice of appeal and a privy councillor in 1877, at the early age of thirty-nine, but died only three years later.

CHELMSFORD, a market town and municipal borough, and the county town of Essex, England, in the Chelmsford parliamentary division, 30 m. E.N.E. from London by the Great Eastern railway. Pop. (1901) 12,580. It is situated in the valley of the Chelmer, at the confluence of the Cann, and has communication by the river with Maldon and the Blackwater estuary 11 m. east. Besides the parish church of St Mary, a graceful Perpendicular edifice, largely rebuilt, the town has a grammar school founded by Edward VI., an endowed charity school and a museum. It is the seat of the county assizes and quarter sessions, and has a handsome shire hall; the county gaol is near the town. Its corn and cattle markets are among the largest in the county; for the first a fine exchange is provided. In the centre of the square in which the corn exchange is situated stands a bronze statue of Lord Chief-Justice Tindal (1776-1846), a native of the parish. There are agricultural implement and iron foundries, large electric light and engineering works, breweries, tanneries, maltings and extensive corn mills. There is a race-course 2 m. south of the town. The borough is under a mayor, 6 aldermen and 18 councillors. Area 2308 acres.

A place of settlement since Palaeolithic times, Chelmsford (Chilmersford, Chelmeresford, Chelmesford) owed its importance to its position on the road from London to Colchester. It consisted of two manors: that of Moulsham, which remained in the possession of Westminster Abbey from Saxon times till the reign of Henry VIII., when it was granted to Thomas Mildmay; and that of Bishop’s Hall, which was held by the bishops of London from the reign of Edward the Confessor to 1545, when it passed to the crown and was granted to Thomas Mildmay in 1563. The medieval history of Chelmsford centred round the manor of Bishop’s Hall. Early in the 12th century Bishop Maurice built the bridge over the Chelmer which brought the road from London directly through the town, thus making it an important stopping-place. The town was not incorporated until 1888. In 1225 Chelmsford was made the centre for the collection of fifteenths from the county of Essex, and in 1227 it became the regular seat of assizes and quarter-sessions. Edward I. confirmed Bishop Richard de Gravesend in his rights of frank pledge in Chelmsford in 1290, and in 1395 Richard II. granted the return of writs to Bishop Robert de Braybroke. In 1377 writs were issued for the return of representatives from Chelmsford to parliament, but no return of members has been found. In 1199 the bishop obtained the grant of a weekly market at the yearly rent of one palfrey, and in 1201 that of an annual fair, now discontinued, for four days from the feast of St Philip and St James.

CHELSEA, a western metropolitan borough of London, England, bounded E. by the city of Westminster, N.W. by Kensington, S.W. by Fulham, and S. by the river Thames. Pop. (1901) 73,842. Its chief thoroughfare is Sloane Street, containing handsome houses and good shops, running south from Knightsbridge to Sloane Square. Hence King’s Road leads west, a wholly commercial highway, named in honour of Charles II., and recalling the king’s private road from St James’s Palace to Fulham, which was maintained until the reign of George IV. The main roads south communicate with the Victoria or Chelsea, Albert and Battersea bridges over the Thames. The beautiful Chelsea embankment, planted with trees and lined with fine houses and, in part, with public gardens, stretches between Victoria and Battersea bridges. The better residential portion of Chelsea is the eastern, near Sloane Street and along the river; the western, extending north to Fulham Road, is mainly a poor quarter.

Chelsea, especially the riverside district, abounds in historical associations. At Cealchythe a synod was held in 785. A similar name occurs in a Saxon charter of the 11th century and in Domesday; in the 16th century it is Chelcith. The later termination ey or ea was associated with the insular character of the land, and the prefix with a gravel bank (ceosol; cf. Chesil Bank, Dorsetshire) thrown up by the river; but the early suffix hythe is common in the meaning of a haven. The manor was originally in the possession of Westminster Abbey, but its history is fragmentary until Tudor times. It then came into the hands of Henry VIII., passed from him to his wife Catharine Parr, and thereafter had a succession of owners, among whom were the Howards, to whom it was granted by Queen Elizabeth, and the Cheynes, from whom it was purchased in 1712 by Sir Hans Sloane, after which it passed to the Cadogans. The memorials which crowd the picturesque church and churchyard of St Luke near the river, commonly known as the Old Church, to a great extent epitomize the history of Chelsea. Such are those of Sir Thomas More (d. 1535); Lord Bray, lord of the manor (1539), his father and son; Lady Jane Guyldeford, duchess of Northumberland, who died “at her maner of Chelse” 25 in 1555; Lord and Lady Dacre (1594-1595); Sir John Lawrence (1638); Lady Jane Cheyne (1698); Francis Thomas, “director of the china porcelain manufactory, Lawrence Street, Chelsea” (1770); Sir Hans Sloane (1753); Thomas Shadwell, poet laureate (1602); Woodfall the printer of Junius (1844), and many others. More’s tomb is dated 1532, as he set it up himself, though it is doubtful whether he lies beneath it. His house was near the present Beaufort Street. In the 18th and 19th centuries Chelsea, especially the parts about the embankment and Cheyne Walk, was the home of many eminent men, particularly of writers and artists, with whom this pleasant quarter has long been in favour. Thus in the earlier part of the period named, Atterbury and Swift lived in Church Lane, Steele and Smollett in Monmouth House. Later, the names of Turner, Rossetti, Whistler, Leigh Hunt, Carlyle (whose house in Cheyne Row is preserved as a public memorial), Count D’Orsay, and Isambard Brunel, are intimately connected with Chelsea. At Lindsey House Count Zinzendorf established a Moravian Society (c. 1750). Sir Robert Walpole’s residence was extant till 1810; and till 1824 the bishops of Winchester had a palace in Cheyne Walk. Queen’s House, the home of D.G. Rossetti (when it was called Tudor House), is believed to take name from Catharine of Braganza.

Chelsea was noted at different periods for two famous places of entertainment, Ranelagh (q.v.) in the second half of the 18th century, and Cremorne Gardens (q.v.) in the middle of the 19th. Don Saltero’s museum, which formed the attraction of a popular coffee-house, was formed of curiosities from Sir Hans Sloane’s famous collections. It was Sloane who gave to the Apothecaries’ Company the ground which they had leased in 1673 for the Physick Garden, which is still extant, but ceased in 1902 to be maintained by the Company. At Chelsea Sir John Danvers (d. 1655) introduced the Italian style of gardening which was so greatly admired by Bacon and soon after became prevalent in England. Chelsea was formerly famous for a manufacture of buns; the original Chelsea bun-house, claiming royal patronage, stood until 1839, and one of its successors until 1888. The porcelain works existed for some 25 years before 1769, when they were sold and removed to Derby. Examples of the original Chelsea ware (see Ceramics) are of great value.

Of buildings and institutions the most notable is Chelsea Royal Hospital for invalid soldiers, initiated by Charles II. (according to tradition on the suggestion of Nell Gwynne), and opened in 1694. The hospital itself accommodates upwards of 500 men, but a system of out-pensioning was found necessary from the outset, and now relieves large numbers throughout the empire. The picturesque building by Wren stands in extensive grounds, which include the former Ranelagh Gardens. A theological college (King James’s) formerly occupied the site; it was founded in 1610 and was intended to be of great size, but the scheme was unsuccessful, and only a small part of the buildings was erected. In the vicinity are the Chelsea Barracks (not actually in the borough). The Royal Military Asylum for boys, commonly called the Duke of York’s school, founded in 1801 by Frederick, duke of York, for the education of children connected with the army, was removed in 1909 to new quarters at Dover. Other institutions are the Whitelands training college for school-mistresses, in which Ruskin took deep interest; the St Mark’s college for school-masters; the Victoria and the Cheyne hospitals for children, a cancer hospital, the South-western polytechnic, and a public library containing an excellent collection relative to local history.

The parliamentary borough of Chelsea returns one member, and includes, as a detached portion, Kensal Town, north of Kensington. The borough council consists of a mayor, 6 aldermen and 36 councillors. Area, 659.6 acres.

CHELSEA, a city of Suffolk county, Massachusetts, U.S.A., a suburb of Boston. Pop. (1890) 27,909; (1900) 34,072, of whom 11,203 were foreign-born; (1910) 32,452. It is situated on a peninsula between the Mystic and Chelsea rivers, and Charlestown and East Boston, and is connected with East Boston and Charlestown by bridges. It is served by the Boston & Maine and (for freight) by the Boston & Albany railways. The United States maintains here naval and marine hospitals, and the state a soldiers’ home. Chelsea’s interests are primarily industrial. The value of the city’s factory products in 1905 was $13,879,159, the principal items being rubber and elastic goods ($3,635,211) and boots and shoes ($2,044,250.) The manufacture of stoves, and of mucilage and paste are important industries. Flexible tubing for electric wires (first made at Chelsea 1889) and art tiles are important products. The first settlement was established in 1624 by Samuel Maverick (c. 1602-c. 1670), the first settler (about 1629) of Noddle’s Island (or East Boston), and one of the first slave-holders in Massachusetts; a loyalist and Churchman, in 1664 he was appointed with three others by Charles II. on an important commission sent to Massachusetts and the other New England colonies (see Nicolls, Richard), and spent the last years of his life in New York. Until 1739, under the name of Winnisimmet, Chelsea formed a part of Boston, but in that year it was made a township; it became a city in 1857. In May 1775 a British schooner in the Mystic defended by a force of marines was taken by colonial militia under General John Stark and Israel Putnam,—one of the first conflicts of the War of Independence. A terrible fire swept the central part of the city on the 12th of April 1908.

CHELTENHAM, a municipal and parliamentary borough of Gloucestershire, England, 109 m. W. by N. of London by the Great Western railway; served also by the west and north line of the Midland railway. Pop. (1901) 49,439. The town is well situated in the valley of the Chelt, a small tributary of the Severn, under the high line of the Cotteswold Hills to the east, and is in high repute as a health resort. Mineral springs were accidentally discovered in 1716. The Montpellier and Pittville Springs supply handsome pump rooms standing in public gardens, and are the property of the corporation. The Montpellier waters are sulphated, and are valuable for their diuretic effect, and as a stimulant to the liver and alimentary canal. The alkaline-saline waters of Pittville are efficacious against diseases resulting from excess of uric acid. The parish church of St Mary dates from the 14th century, but is almost completely modernized. The town, moreover, is wholly modern in appearance. Assembly rooms opened in 1815 by the duke of Wellington were removed in 1901. A new town hall, including a central spa and assembly rooms, was opened in 1903. There are numerous other handsome buildings, especially in High Street, and the Promenade forms a beautiful broad thoroughfare, lined with trees. The town is famous as an educational centre. Cheltenham College (1842) provides education for boys in three departments, classical, military and commercial; and includes a preparatory school. The Ladies’ College (1854), long conducted by Miss Beale (q.v.), is one of the most successful in England. The Normal Training College was founded in 1846 for the training of teachers, male and female, in national and parochial schools. A free grammar school was founded in 1568 by Richard Pate, recorder of Gloucester. The art gallery and museum may be mentioned also. The parliamentary borough returns one member. The municipal borough is under a mayor, 6 aldermen and 18 councillors. Area, 4726 acres. The urban district of Charlton Kings (pop. 3806) forms a south-eastern suburb of Cheltenham.

The site of a British village and burying-ground, Cheltenham (Celtanhomme, Chiltham, Chelteham) was a village with a church in 803. The manor belonged to the crown; it was granted to Henry de Bohun, earl of Hereford, late in the 12th century, but in 1199 was exchanged for other lands with the king. It was granted to William de Longespée, earl of Salisbury, in 1219, but resumed on his death and granted in dower to Eleanor of Provence in 1243. In 1252 the abbey of Fécamp purchased the manor, and it afterwards belonged to the priory of Cormeille, but was confiscated in 1415 as the possession of an alien priory, and was granted in 1461 to the abbey of Lyon, by which it was held until, once more returning to the crown at the Dissolution, 26 it was granted to the family of Dutton. The town is first mentioned in 1223, when William de Longespée leased the benefit of the markets, fairs and hundred of Cheltenham to the men of the town for three years; the lease was renewed by Henry III. in 1226, and again in 1230 for ten years. A market town in the time of Camden, it was governed by commissioners from the 18th century in 1876, when it was incorporated; it became a parliamentary borough in 1832. Henry III. in 1230 had granted to the men of Cheltenham a market on each Thursday, and a fair on the vigil, feast and morrow of St James. Although Camden mentions a considerable trade in malt, the spinning of woollen yarn was the only industry in 1779. After the discovery of springs in 1716, and the erection of a pump-room in 1738, Cheltenham rapidly became fashionable, the visit of George III. and the royal princesses in 1788 ensuring its popularity.

CHELYABINSK, a town of Russia, in the Orenburg government, at the east foot of the Urals, is the head of the Siberian railway, 624 m. by rail E.N.E. of Samara and 154 m. by rail S.S.E. of Ekaterinburg. Pop. (1900) 25,505. It has tanneries and distilleries, and is the centre of the trade in corn and produce of cattle for the Ural iron-works. The town was founded in 1658.

CHELYS (Gr. χέλυς, tortoise; Lat. testudo), the common lyre of the ancient Greeks, which had a convex back of tortoiseshell or of wood shaped like the shell. The word chelys was used in allusion to the oldest lyre of the Greeks which was said to have been invented by Hermes. According to tradition he was attracted by sounds of music while walking on the banks of the Nile, and found they proceeded from the shell of a tortoise across which were stretched tendons which the wind had set in vibration (Homeric Hymn to Hermes, 47-51). The word has been applied arbitrarily since classic times to various stringed instruments, some bowed and some twanged, probably owing to the back being much vaulted. Kircher (Musurgia, i. 486) applied the name of chelys to a kind of viol with eight strings. Numerous representations of the chelys lyre or testudo occur on the Greek vases, in which the actual tortoiseshell is depicted; a good illustration is given in Le Antichità, di Ercolano (vol. i. pl. 43). Propertius (iv. 6) calls the instrument the lyra testudinea. Scaliger (on Manilius, Astronomicon, Proleg. 420) was probably the first writer to draw attention to the difference, between chelys and cithara (q.v.).

CHEMICAL ACTION, the term given to any process in which change in chemical composition occurs. Such processes may be set up by the application of some form of energy (heat, light, electricity, &c.) to a substance, or by the mixing of two or more substances together. If two or more substances be mixed one of three things may occur. First, the particles may be mechanically intermingled, the degree of association being dependent upon the fineness of the particles, &c. Secondly, the substances may intermolecularly penetrate, as in the case of gas-mixtures and solutions. Or thirdly they may react chemically. The question whether, in any given case, we have to deal with a physical mixture or a chemical compound is often decided by the occurrence of very striking phenomena. To take a simple example:—oxygen and hydrogen are two gases which may be mixed in all proportions at ordinary temperatures, and it is easy to show that the properties of the products are simply those of mixtures of the two free gases. If, however, an electric spark be passed through the mixtures, powerful chemical union ensues, with its concomitants, great evolution of heat and consequent rise of temperature, and a compound, water, is formed which presents physical and chemical properties entirely different from those of its constituents.

In general, powerful chemical forces give rise to the evolution of large quantities of heat, and the properties of the resulting substance differ vastly more from those of its components than is the case with simple mixtures. This constitutes a valuable criterion as to whether mere mixture is involved on the one hand, or strong chemical union on the other. When, however, the chemical forces are weak and the reaction, being incomplete, leads to a state of chemical equilibrium, in which all the reacting substances are present side by side, this criterion vanishes. For example, the question whether a salt combines with water molecules when dissolved in water cannot be said even yet to be fully settled, and, although there can be no doubt that solution is, in many cases, attended by chemical processes, still we possess as yet no means of deciding, with certainty, how many molecules of water have bound themselves to a single molecule of the dissolved substance (solute). On the other hand, we possess exact methods of testing whether gases or solutes in dilute solution react one with another and of determining the equilibrium state which is attained. For if one solute react with another on adding the latter to its solution, then corresponding to the decrease of its concentration there must also be a decrease of vapour pressure, and of solubility in other solvents; further, in the case of a mixture of gases, the concentration of each single constituent follows from its solubility in some suitable solvent. We thus obtain the answer to the question: whether the concentration of a certain constituent has decreased during mixing, i.e. whether it has reacted chemically.

When a compound can be obtained in a pure state, analysis affords us an important criterion of its chemical nature, for unlike mixtures, the compositions of which are always variable within wider or narrower limits, chemical compounds present definite and characteristic mass-relations, which find full expression in the atomic theory propounded by Dalton (see Atom). According to this theory a mixture is the result of the mutual interpenetration of the molecules of substances, which remain unchanged as such, whilst chemical union involves changes more deeply seated, inasmuch as new molecular species appear. These new substances, if well-defined chemical compounds, have a perfectly definite composition and contain a definite, generally small, number of elementary atoms, and therefore the law of constant proportions follows at once, and the fact that only an integral number of atoms of any element may enter into the composition of any molecule determines the law of multiple proportions.

These considerations bring us face to face with the task of more closely investigating the nature of chemical forces, in other words, of answering the question: Nature of chemical forces. what forces guide the atoms in the formation of a new molecular species? This problem is still far from being completely answered, so that a few general remarks must suffice here.

It is remarkable that among the most stable chemical compounds, we find combinations of atoms of one and the same element. Thus, the stability of the di-atomic molecule N2 is so great, that no trace of dissociation has yet been proved even at the highest temperatures, and as the constituent atoms of the molecule N2 must be regarded as absolutely identical, it is clear that “polar” forces cannot be the cause of all chemical action. On the other hand, especially powerful affinities are also at work when so-called electro-positive and electro-negative elements react. The forces which here come into play appear to be considerably greater than those just mentioned; for instance, potassium fluoride is perhaps the most stable of all known compounds.

It is also to be noticed that the combinations of the electro-negative elements (metalloids) with one another exhibit a metalloid character, and also we find, in the mutual combinations of metals, all the characteristics of the metallic state; but in the formation of a salt from a metal and a metalloid we have an entirely new substance, quite different from its components; and at the same time, the product is seen to be an electrolyte, i.e. to have the power of splitting up into a positively and a negatively charged constituent when dissolved in some solvent. These considerations lead to the conviction that forces of a “polar” origin play an important part here, and indeed we may make the general surmise that in the act of chemical combination forces of both a non-polar and polar nature play a part, and that the latter are in all probability identical with the electric forces.

It now remains to be asked—what are the laws which govern 27 the action of these forces? This question is of fundamental importance, since it leads directly to those laws which regulate the chemical process. Besides the already mentioned fundamental law of chemical combination, that of constant and multiple proportions, there is the law of chemical mass-action, discovered by Guldberg and Waage in 1867, which we will now develop from a kinetic standpoint.

Kinetic Basis of the Law of Chemical Mass-action.—We will assume that the molecular species A1, A2, ... A′1, A′2, ... are present in a homogeneous system, where they can react on each other only according to the scheme

A1 + A2 + ... ↔ A′1 + A′2 + ...;

this is a special case of the general equation

n1A1 + n2A2 + ... ↔ n′1A′1 + n′2A′2 + ...,

in which only one molecule of each substance takes part in the reaction. The reacting substances may be either gaseous or form a liquid mixture, or be dissolved in some selected solvent; but in each case we may state the following considerations regarding the course of the reaction. For a transformation to take place from left to right in the sense of the reaction equation, all the molecules A1, A2, ... must clearly collide at one point; otherwise no reaction is possible, since we shall not consider side-reactions. Such a collision need not of course bring about that transposition of the atoms of the single molecules which constitutes the above reaction. Much rather must it be of such a kind as is favourable to that loosening of the bonds that bind the atoms in the separate molecules, which must precede this transposition. Of a large number of such collisions, therefore, only a certain smaller number will involve a transposition from left to right in the sense of the equation. But this number will be the same under the same external conditions, and the greater the more numerous the collisions; in fact a direct ratio must exist between the two. Bearing in mind now, that the number of collisions must be proportional to each of the concentrations of the bodies A1, A2, ..., and therefore, on the whole, to the product of all these concentrations, we arrive at the conclusion that the velocity v of the transposition from left to right in the sense of the reaction equation is v = kc1c2 ..., in which c1, c2, ... represent the spatial concentrations, i.e. the number of gram-molecules of the substances A1, A2, ... present in one litre, and k is, at a given temperature, a constant which may be called the velocity-coefficient.

Exactly the same consideration applies to the molecules A′1, A′2.... Here the velocity of the change from right to left in the sense of the reaction-equation increases with the number of collisions of all these molecules at one point, and this is proportional to the product of all the concentrations. If k’ denotes the corresponding proportionality-factor, then the velocity v’ of the change from right to left in the sense of the reaction-equation is v′ = k′c′1c′2.... These spatial concentrations are often called the “active masses” of the reacting components. Hence the reaction-velocity in the sense of the reaction-equation from left to right, or the reverse, is proportional to the product of the “active-masses” of the left-hand or right-hand components respectively.

Neither v nor v′ can be separately investigated, and the measurements of the course of a reaction always furnish only the difference of these two quantities. The reaction-velocity Law of chemical statics. actually observed represents the difference of these two partial reaction-velocities, whilst the amount of change observed during any period of time is equal to the change in the one direction, minus the change in the opposite direction. It must not be assumed, however, that on the attainment of equilibrium all action has ceased, but rather that the velocity of change in one direction has become equal to that in the opposite direction, with the result that no further total change can be observed, i.e. the system has reached equilibrium, for which the relation v - v′ = 0 must therefore hold, or what is the same thing

kc1c2 ... = k’c’1c’2 ...,

this is the fundamental law of chemical statics.

The conception that the equilibrium is not to be attributed to absolute indifference between the reacting bodies, but that these continue to exert their mutual actions undiminished and the opposing changes now balance, is of fundamental significance in the interpretation of changes of matter in general. This is generally expressed in the form: the equilibrium in this and other analogous cases is not static but dynamic. This conception was a direct result of the kinetic-molecular considerations, and was applied with special success to the development of the kinetic theory of gases. Thus with Clausius, we conceive the equilibrium of water-vapour with water, not as if neither water vaporized nor vapour condensed, but rather as though the two processes went on unhindered in the equilibrium state, i.e. during contact of saturated vapour with water, in a given time, as many water molecules passed through the water surface in one direction as in the opposite direction. This view, as applied to chemical changes, was first advanced by A.W. Williamson (1851), and further developed by C.M. Guldberg and P. Waage and others.

From the previous considerations it follows that the reaction-velocity at every moment, i.e. the velocity with which the chemical process advances towards the Law of chemical kinetics. equilibrium state, is given by the equation

V = v - v′ = kc1c2 ... - k′c′1c′2 ...;

this states the fundamental law of chemical kinetics.

The equilibrium equation is simply a special case of this more general one, and results when the total velocity is written zero, just as in analytical mechanics the equilibrium conditions follow at once by specialization of the general equations of motion.

No difficulty presents itself in the generalization of the previous equations for the reaction which proceeds after the scheme

n1A1 + n2A2 + ... = n′1A′1 + n′2A′2 + ...,

where n1, n2, ..., n′1, n′2, ... denote the numbers of molecules of the separate substances which take part in the reaction, and are therefore whole, mostly small, numbers (generally one or two, seldom three or more). Here as before, v and v′ are to be regarded as proportional to the number of collisions at one point of all molecules necessary to the respective reaction, but now n1 molecules of A1, n2 molecules of A2, &c., must collide for the reaction to advance from left to right in the sense of the equation; and similarly n′1 molecules of A′1, n′2 molecules of A′2, &c., must collide for the reaction to proceed in the opposite direction. If we consider the path of a single, arbitrarily chosen molecule over a certain time, then the number of its collisions with other similar molecules will be proportional to the concentration C of that kind of molecule to which it belongs. The number of encounters between two molecules of the kind in question, during the same time, will be in general C times as many, i.e. the number of encounters of two of the same molecules is proportional to the square of the concentration C; and generally, the number of encounters of n molecules of one kind must be regarded as proportional to the nth power of C, i.e. Cn.

The number of collisions of n1 molecules of A1, n2 molecules of A2 ... is accordingly proportional to C1n1C2n2 ..., and the reaction-velocity corresponding to it is therefore

v = kC1n1C2n2 ...,

and similarly the opposed reaction-velocity is

v′ = k′C′1n′1C′2n′2 ...;

the resultant reaction-velocity, being the difference of these two partial velocities, is therefore

V = v - v′ = kC1n1C2n2 ... - k′C′1n′1C′2n′2 ...

This is the most general expression of the law of chemical mass-action, for the case of homogeneous systems.

Equating V to zero, we obtain the equation for the equilibrium state, viz.

C1n1C2n2 ... / C′1n′1C′2n′2 ... = k / k′ = K;

K is called the “equilibrium-constant.”

28

These formulae hold for gases and for dilute solutions, but assume the system to be homogeneous, i.e. to be either a homogeneous gas-mixture or a homogeneous dilute solution. Limitations and applications of the laws. The case in which other states of matter share in the equilibrium permits of simple treatment when the substances in question may be regarded as pure, and consequently as possessing definite vapour-pressures or solubilities at a given temperature. In this case the molecular species in question, which is, at the same time, present in excess and is hence usually, called a Bodenkörper, must possess a constant concentration in the gas-space or solution. But since the left-hand side of the last equation contains only variable quantities, it is simplest and most convenient to absorb these constant concentrations into the equilibrium-constant; whence we have the rule: leave the molecular species present as Bodenkörper out of account, when determining the concentration-product. Guldberg and Waage expressed this in the form “the active mass of a solid substance is constant.” The same is true of liquids when these participate in the pure state in the equilibrium, and possess therefore a definite vapour-pressure or solubility. When, finally, we are not dealing with a dilute solution but with any kind of mixture whatever, it is simplest to apply the law of mass-action to the gaseous mixture in equilibrium with this. The composition of the liquid mixture is then determinable when the vapour-pressures of the separate components are known. This, however, is not often the case; but in principle this consideration is important, since it involves the possibility of extending the law of chemical mass-action from ideal gas-mixtures and dilute solutions, for which it primarily holds, to any other system whatever.

The more recent development of theoretical chemistry, as well as the detailed study of many chemical processes which have found technical application, leads more and more convincingly to the recognition that in the law of chemical mass-action we have a law of as fundamental significance as the law of constant and multiple proportions. It is therefore not without interest to briefly touch upon the development of the doctrine of chemical affinity.

Historical Development of the Law of Mass-action.—The theory developed by Torbern Olof Bergman in 1775 must be regarded as the first attempt of importance to account for the mode of action of chemical forces. The essential principle of this may be stated as follows:—The magnitude of chemical affinity may be expressed by a definite number; if the affinity of the substance A is greater for the substance B than for the substance C, then the latter (C) will be completely expelled by B from its compound with A, in the sense of the equation A·C + B = A·B + C. This theory fails, however, to take account of the influence of the relative masses of the reacting substances, and had to be abandoned as soon as such an influence was noticed. An attempt to consider this factor was made by Claude Louis Berthollet (1801), who introduced the conception of chemical equilibrium. The views of this French chemist may be summed up in the following sentence:—Different substances have different affinities for each other, which only come into play on immediate contact. The condition of equilibrium depends not only upon the chemical affinity, but also essentially upon the relative masses of the reacting substances.

Essentially, Berthollet’s idea is to-day the guiding principle of the doctrine of affinity. This is especially true of our conceptions of many reactions which, in the sense of Bergman’s idea, proceed to completion, i.e. until the reacting substances are all used up; but only for this reason, viz. that one or more of the products of the reaction is removed from the reaction mixture (either by crystallization, evaporation or some other process), and hence the reverse reaction becomes impossible. Following Berthollet’s idea, two Norwegian investigators, C.M. Guldberg and Peter Waage, succeeded in formulating the influence of the reacting masses in a simple law—the law of chemical mass-action already defined. The results of their theoretical and experimental studies were published at Christiania in 1867 (Études sur les affinités chimiques); this work marks a new epoch in the history of chemistry. Even before this, formulae to describe the progress of certain chemical reactions, which must be regarded as applications of the law of mass-action, had been put forward by Ludwig Wilhelmy (1850), and by A.G. Vernon-Harcourt and William Esson (1856), but the service of Guldberg and Waage in having grasped the law in its full significance and logically applied it in all directions, remains of course undiminished. Their treatise remained quite unknown; and so it happened that John Hewitt Jellett (1873), J.H. van’t Hoff (1877), and others independently developed the same law. The thermodynamic basis of the law of mass-action is primarily due to Horstmann, J. Willard Gibbs and van’t Hoff.

Applications.—Let us consider, as an example of the application of the law of mass-action, the case of the dissociation of water-vapour, which takes place at high temperatures in the sense of the equation 2H2O = 2H2 + O2. Representing the concentrations of the corresponding molecular species by [H2], &c., the expression [H2]² [O2] / [H2O]² must be constant at any given temperature. This shows that the dissociation is set back by increasing the pressure; for if the concentrations of all three kinds of molecules be increased by strong compression, say to ten times the former amounts, then the numerator is increased one thousand, the denominator only one hundred times. Hence if the original equilibrium-constant is to hold, the dissociation must go back, and, what is more, by an exactly determinable amount. At 2000° C. water-vapour is only dissociated to the extent of a few per cent; therefore, even when only a small excess of oxygen or hydrogen be present, the numerator in the foregoing expression is much increased, and it is obvious that in order to restore the equilibrium state, the concentration of the other component, hydrogen or oxygen as the case may be, must diminish. In the case of slightly dissociated substances, therefore, even a relatively small excess of one component is sufficient to set back the dissociation substantially.

Chemical Kinetics.—It has been already mentioned that the law of chemical mass-action not only defines the conditions for chemical equilibrium, but contains at the same time the principles of chemical kinetics. The previous considerations show indeed that the actual progress of the reaction is determined by the difference of the reaction-velocities in the one and the other (opposed) direction, in the sense of the corresponding reaction-equation. Since the reaction-velocity is given by the amount of chemical change in a small interval of time, the law of chemical mass-action supplies a differential equation, which, when integrated, provides formulae which, as numerous experiments have shown, very happily summarize the course of the reaction. For the simplest case, in which a single species of molecule undergoes almost complete decomposition, so that the reaction-velocity in the reverse direction may be neglected, we have the simple equation

dx/dt = k(a-x)

and if x = 0 when t = 0 we have by integration

k = t-1 log {a / (a-x) }.

We will now apply these conclusions to the theory of the ignition of an explosive gas-mixture, and in particular to the combustion of “knallgas” (a mixture of hydrogen Theory of explosive combustion. and oxygen) to water-vapour. At ordinary temperatures knallgas undergoes practically no change, and it might be supposed that the two gases, oxygen and hydrogen, have no affinity for each other. This conclusion, however, is shown to be incorrect by the observation that it is only necessary to add some suitable catalyst such as platinum-black in order to immediately start the reaction. We must therefore conclude that even at ordinary temperatures strong chemical affinity is exerted between oxygen and hydrogen, but that at low temperatures this encounters great frictional resistances, or in other words that the reaction-velocity is very small. It is a matter of general experience that the resistances which the chemical forces have to overcome diminish with rising temperature, i.e. the reaction-velocity increases with temperature. Therefore, when we warm the knallgas, the number of collisions of oxygen and hydrogen molecules favourable to the formation 29 of water becomes greater and greater, until at about 500° the gradual formation of water is observed, while at still higher temperatures the reaction-velocity becomes enormous. We are now in a position to understand what is the result of a strong local heating of the knallgas, as, for example, by an electric spark. The strongly heated parts of the knallgas combine to form water-vapour with great velocity and the evolution of large amounts of heat, whereby the adjacent parts are brought to a high temperature and into a state of rapid reaction, i.e. we observe an ignition of the whole mixture. If we suppose the knallgas to be at a very high temperature, then its combustion will be no longer complete owing to the dissociation of water-vapour, whilst at extremely high temperatures it would practically disappear. Hence it is clear that knallgas appears to be stable at low temperatures only because the reaction-velocity is very small, but that at very high temperatures it is really stable, since no chemical forces are then active, or, in other words, the chemical affinity is very small.

The determination of the question whether the failure of some reaction is due to an inappreciable reaction-velocity or to absence of chemical affinity, is of fundamental importance, and only in the first case can the reaction be hastened by catalysts.

Many chemical compounds behave like knallgas. Acetylene is stable at ordinary temperatures, inasmuch as it only decomposes slowly; but at the same time it is explosive, for the decomposition when once started is rapidly propagated, on account of the heat evolved by the splitting up of the gas into carbon and hydrogen. At very high temperatures, however, acetylene acquires real stability, since carbon and hydrogen then react to form acetylene.

Many researches have shown that the combustion of an inflammable gas-mixture which is started at a point, e.g. by an electric spark, may be propagated in two essentially Explosion-waves. different ways. The characteristic of the slower combustion consists in this, viz. that the high temperature of the previously ignited layer spreads by conduction, thereby bringing the adjacent layers to the ignition-temperature; the velocity of the propagation is therefore conditioned in the first place by the magnitude of the conductivity for heat, and more particularly, in the second place, by the velocity with which a moderately heated layer begins to react chemically, and so to rise gradually in temperature, i.e. essentially by the change of reaction-velocity with temperature. A second entirely independent mode of propagation of the combustion lies at the basis of the phenomenon that an explosive gas-mixture can be ignited by strong compression or—more correctly—by the rise of temperature thereby produced. The increase of the concentrations of the reacting substances consequent upon this increase of pressure raises the reaction-velocity in accordance with the law of chemical mass-action, and so enormously favours the rapid evolution of the heat of combustion.

It is therefore clear that such a powerful compression-wave can not only initiate the combustion, but also propagate it with extremely high velocity. Indeed a compression-wave of this kind passes through the gas-mixture, heated by the combustion to a very high temperature. It must, however, be propagated considerably faster than an ordinary compression-wave, for the result of ignition in the compressed (still unburnt) layer is the production of a very high pressure, which must in accordance with the principles of wave-motion increase the velocity of propagation. The absolute velocity of the explosion-wave would seem, in the light of these considerations, to be susceptible of accurate calculation. It is at least clear that it must be considerably higher than the velocity of sound in the mass of gas strongly heated by the explosion, and this is confirmed by actual measurements (see below) which show that the velocity of the explosion-wave is from one and a half times to double that of sound-waves at the combustion temperature.

We are now in a position to form the following picture of the processes which follow upon the ignition of a combustible gas-mixture contained in a long tube. First we have the condition of slow combustion; the heat is conveyed by conduction to the adjacent layers, and there follows a velocity of propagation of a few metres per second. But since the combustion is accompanied by a high increase of pressure, the adjacent, still unburnt layers are simultaneously compressed, whereby the reaction-velocity increases, and the ignition proceeds faster. This involves still greater compression of the next layers, and so if the mixture be capable of sufficiently rapid combustion, the velocity of propagation of the ignition must continually increase. As soon as the compression in the still unburnt layers becomes so great that spontaneous ignition results, the now much more pronounced compression-waves excited with simultaneous combustion must be propagated with very great velocity, i.e. we have spontaneous development of an “explosion-wave.” M.P.E. Berthelot, who discovered the presence of such explosion-waves, proved their velocity of propagation to be independent of the pressure, the cross-section of the tubes in which the explosive gas-mixture is contained, as well as of the material of which these are made, and concluded that this velocity is a constant, characteristic of the particular mixture. The determination of this velocity is naturally of the highest interest.

In the following table Berthelot’s results are given along with the later (1891) concordant ones of H.B. Dixon, the velocities of propagation of explosions being given in metres per second.

The maximum pressure of the explosion-wave possesses very high values; it appears that a compression of from 1 to 30-40 atmospheres is necessary to produce spontaneous ignition of mixtures of oxygen and hydrogen. But since the heat evolved in the path of the explosion causes a rise of temperature of 2000°-3000°, i.e. a rise of absolute temperature about four times that directly following upon the initial compression, we are here concerned with pressures amounting to considerably more than 100 atmospheres. Both the magnitude of this pressure and the circumstance that it so suddenly arises are peculiar to the very powerful forces which distinguish the explosion-wave from the slow combustion-wave.

Nascent State.—The great reactive power of freshly formed or nascent substances (status nascens)may be very simply referred to the principles of mass-action. As is well known, this phenomenon is specially striking in the case of hydrogen, which may therefore be taken as a typical example. The law of mass-action affirms the action of a substance to be the greater the higher its concentration, or, for a gas, the higher its partial-pressure. Now experience teaches that those metals which liberate hydrogen from acids are able to supply the latter under extremely high pressure, and we may therefore assume that the hydrogen which results, for example, from the action of zinc upon sulphuric acid is initially under very high pressures which are then afterwards relieved. Hence the hydrogen during liberation exhibits much more active powers of reduction than the ordinary gas.

A deeper insight into the relations prevailing here is offered from the atomistic point of view. From this we are bound to conclude that the hydrogen is in the first instance evolved in the form of free atoms, and since the velocity of the reaction H + H = H2 at ordinary temperatures, though doubtless very great, is not practically instantaneous, the freshly generated hydrogen will contain a remnant of free atoms, which are able to react both more actively and more rapidly. Similar considerations are of course applicable to other cases.

Ion-reactions.—The application of the law of chemical mass 30 action is much simplified in the case in which the reaction-velocity is enormously great, when practically an instantaneous adjustment of the equilibrium results. Only in this case can the state of the system, which pertains after mixing the different components, be determined merely from knowledge of the equilibrium-constant. This case is realized in the reactions between gases at very high temperatures, which have, however, been little investigated, and especially by the reactions between electrolytes, the so-called ion-reactions. In this latter case, which has been thoroughly studied on account of its fundamental importance for inorganic qualitative and quantitative analysis, the degrees of dissociation of the various electrolytes (acids, bases and salts) are for the most part easily determined by the aid of the freezing-point apparatus, or of measurements of the electric conductivity; and from these data the equilibrium-constant K may be calculated. Moreover, it can be shown that the state of the system can be determined when the equilibrium constants of all the electrolytes which are present in the common solution are known. If this be coupled with the law that the solubility of solid substances, as with vapour-pressures, is independent of the presence of other electrolytes, it is sufficient to know the solubilities of the electrolytes in question, in order to be able to determine which substances must participate in the equilibrium in the solid state, i.e. we arrive at the theory of the formation and solution of precipitates.

As an illustration of the application of these principles, we shall deal with a problem of the doctrine of affinity, namely, that of the relative strengths of acids and bases. It Strength of acids and bases. was quite an early and often repeated observation that the various acids and bases take part with very varying intensity or avidity in those reactions in which their acid or basic nature comes into play. No success attended the early attempts at giving numerical expression to the strengths of acids and bases, i.e. of finding a numerical coefficient for each acid and base, which should be the quantitative expression of the degree of its participation in those specific reactions characteristic of acids and bases respectively. Julius Thomsen and W. Ostwald attacked the problem in a far-seeing and comprehensive manner, and arrived at indisputable proof that the property of acids and bases of exerting their effects according to definite numerical coefficients finds expression not only in salt-formation but also in a large number of other, and indeed very miscellaneous, reactions.

When Ostwald compared the order of the strengths of acids deduced from their competition for the same base, as determined by Thomsen’s thermo-chemical or his own volumetric method, with that order in which the acids arrange themselves according to their capacity to bring calcium oxalate into solution, or to convert acetamide into ammonium acetate, or to split up methyl acetate into methyl alcohol and acetic acid catalytically, or to invert cane-sugar, or to accelerate the mutual action of hydriodic on bromic acid, he found that in all these well-investigated and very miscellaneous cases the same succession of acids in the order of their strengths is obtained, whichever one of the above chemical processes be chosen as measure of these strengths. It is to be noticed that all these chemical changes cited took place in dilute aqueous solution, consequently the above order of acids refers only to the power to react under these circumstances. The order of acids proved to be fairly independent of temperature. While therefore the above investigations afforded a definite qualitative solution of the order of acids according to strengths, the determination of the quantitative relations offered great difficulties, and the numerical coefficients, determined from the separate reactions, often displayed great variations, though occasionally also surprising agreement. Especially great were the variations of the coefficients with the concentration, and in those cases in which the concentration of the acid changed considerably during the reaction, the calculation was naturally quite uncertain. Similar relations were found in the investigation of bases, the scope of which, however, was much more limited.

These apparently rather complicated relations were now cleared up at one stroke, by the application of the law of chemical mass-action on the lines indicated by S. Arrhenius in 1887, when he put forward the theory of electrolytic dissociation to explain that peculiar behaviour of substances in aqueous solution first recognized by van’t Hoff in 1885. The formulae which must be made use of here in the calculation of the equilibrium-relations follow naturally by simple application of the law of mass-action to the corresponding ion-concentrations.

The peculiarities which the behaviour of acids and bases presents, and, according to the theory of Arrhenius, must present—peculiarities which found expression in the very early distinction between neutral solutions on the one hand, and acid or basic ones on the other, as well as in the belief in a polar antithesis between the two last—must now, in the light of the theory of electrolytic dissociation, be conceived as follows:—

The reactions characteristic of acids in aqueous solution, which are common to and can only be brought about by acids, find their explanation in the fact that this class of bodies gives rise on dissociation to a common molecular species, namely, the positively charged hydrogen-ion (H+). The specific chemical actions peculiar to acids are therefore to be attributed to the hydrogen-ion just as the actions common to all chlorides are to be regarded as those of the free chlorine-ions. In like manner, the reactions characteristic of bases in solution are to be attributed to the negatively charged hydroxyl-ions (OH-), which result from the dissociation of this class of bodies.

A solution has an acid reaction when it contains an excess of hydrogen-ions, and a basic reaction when it contains an excess of hydroxyl-ions. If an acid and an alkaline solution be brought together mutual neutralization must result, since the positive H-ions and the negative OH-ions cannot exist together in view of the extremely weak conductivity of pure water and its consequent slight electrolytic dissociation, and therefore they must at once combine to form electrically neutral molecules, in the sense of the equation

H+ + OH- = H2O.

In this lies the simple explanation of the “polar” difference between acid and basic solutions. This rests essentially upon the fact that the ion peculiar to acids and the ion peculiar to bases form the two constituents of water, i.e. of that solvent in which we usually study the course of the reaction. The idea of the “strength” of an acid or base at once arises. If we compare equivalent solutions of various acids, the intensity of those actions characteristic of them will be the greater the more free hydrogen-ions they contain; this is an immediate consequence of the law of chemical mass-action. The degree of electrolytic dissociation determines, therefore, the strength of acids, and a similar consideration leads to the same result for bases.

Now the degree of electrolytic dissociation changes with concentration in a regular manner, which is given by the law of mass-action. For if C denote the concentration of the electrolyte and a its degree of dissociation, the above law states that

C²a²/C(1-a) = Ca²/(1-a) = K.

At very great dilutions the dissociation is complete, and equivalent solutions of the most various acids then contain the same number of hydrogen-ions, or, in other words, are equally strong; and the same is true of the hydroxyl-ions of bases. The dissociation also decreases with increasing concentration, but at different rates for different substances, and the relative “strengths” of acids and bases must hence change with concentration, as was indeed found experimentally. The dissociation-constant K is the measure of the variation of the degree of dissociation with concentration, and must therefore be regarded as the measure of the strengths of acids and bases. So that in this special case we are again brought to the result which was stated in general terms above, viz. that the dissociation-coefficient forms the measure of the reactivity of a dissolved electrolyte. Ostwald’s series of acids, based upon the investigation of the most various reactions, should therefore correspond with the order of their dissociation-constants, and further with the 31 order of their freezing-point depressions in equivalent solutions, since the depression of the freezing-point increases with the degree of electrolytic dissociation. Experience confirms this conclusion completely. The degree of dissociation of an acid, at a given concentration, for which its molecular conductivity is Λ, is shown by the theory of electrolytic dissociation to be a = Λ / Λ∞; Λ∞, the molecular conductivity at very great dilution in accordance with the law of Kohlrausch, is u + v, where u and v are the ionic-mobilities (see Conduction, Electric). Since u, the ionic-mobility of the hydrogen ion, is generally more than ten times as great as v, the ionic-mobility of the negative acid-radical, Λ∞ has approximately the same value (generally within less than 10%) for the different acids, and the molecular-conductivity of the acids in equivalent concentration is at least approximately proportional to the degree of electrolytic dissociation, i.e. to the strength.

In general, therefore, the order of conductivities is identical with that in which the acids exert their specific powers. This remarkable parallelism, first perceived by Arrhenius and Ostwald in 1885, was the happy development which led to the discovery of electrolytic dissociation (see Conduction, Electric; and Solution).

Catalysis.—We have already mentioned the fact, early known to chemists, that many reactions proceed with a marked increase of velocity in presence of many foreign substances. With Berzelius we call this phenomenon “catalysis,” by which we understand that general acceleration of reactions which also progress when left to themselves, in the presence of certain bodies which do not change in amount (or only slightly) during the course of the reaction. Acids and bases appear to act catalytically upon all reactions involving consumption or liberation of water, and indeed that action is proportional to the concentration of the hydrogen or hydroxyl-ions. Further, the decomposition of hydrogen peroxide is “catalysed” by iodine-ions, the condensation of two molecules of benzaldehyde to benzoin by cyanogen-ions. One of the earliest known and technically most important instances of catalysis is that of the oxidation of sulphur dioxide to sulphuric acid by oxygen in the presence of oxides of nitrogen. Other well-known and remarkable examples are the catalysis of the combustion of hydrogen and of sulphur dioxide in oxygen by finely-divided platinum. We may also mention the interesting work of Dixon and Baker, which led to the discovery that a large number of gas-reactions, e.g. the combustion of carbon monoxide, the dissociation of sal-ammoniac vapour, and the action of sulphuretted hydrogen upon the salts of heavy metals, cease when water-vapour is absent, or at least proceed with greatly diminished velocity.

“Negative catalysis,” i.e. the retardation of a reaction by addition of some substance, which is occasionally observed, appears to depend upon the destruction of a “positive catalyte” by the body added.

A catalyte can have no influence, however, upon the affinity of a process, since that would be contrary to the second law of thermodynamics, according to which affinity of an isothermal process, which is measured by the maximum work, only depends upon the initial and final states. The effect of a catalyte is therefore limited to the resistances opposing the progress of a reaction, and does not influence its driving-force or affinity. Since the catalyte takes no part in the reaction its presence has no effect on the equilibrium-constant. This, in accordance with the law of mass-action, is the ratio of the separate reaction-velocities in the two contrary directions. A catalyte must therefore always accelerate the reverse-reaction. If the velocity of formation of a body be increased by addition of some substance then its velocity of decomposition must likewise increase. We have an example of this in the well-known fact that the formation, and no less the saponification, of esters, proceeds with increased velocity in the presence of acids, while the observation that in absence of water-vapour neither gaseous ammonium chloride dissociates nor dry ammonia combines with hydrogen chloride becomes clear on the same grounds.

A general theory of catalytic phenomena does not at present exist. The formation of intermediate products by the action of the reacting substance upon the catalyte has often been thought to be the cause of these. These intervening products, whose existence in many cases has been proved, then split up into the catalyte and the reaction-product. Thus chemists have sought to ascribe the influence of oxides of nitrogen on the formation of sulphuric acid to the initial formation of nitrosyl-sulphuric acid, SO2(OH)(NO2), from the mixture of sulphur dioxide, oxides of nitrogen and air, which then reacted with water to form sulphuric and nitrous acids. When the velocity of such intermediate reactions is greater than that of the total change, such an explanation may suffice, but a more certain proof of this theory of catalysis has only been reached in a few cases, though in many others it appears very plausible. Hence it is hardly possible to interpret all catalytic processes on these lines.

In regard to catalysis in heterogeneous systems, especially the hastening of gas-reactions by platinum, it is very probable that it is closely connected with the solution or absorption of the gases on the part of the metal. From the experiments of G. Bredig it seems that colloidal solutions of a metal act like the metal itself. The action of a colloidal-platinum solution on the decomposition of hydrogen peroxide is still sensible even at a dilution of 1/70,000,000 grm.-mol. per litre; indeed the activity of this colloidal-platinum solution calls to mind in many ways that of organic ferments, hence Bredig has called it an “inorganic ferment.” This analogy is especially striking in the change of their activity with time and temperature, and in the possibility, by means of bodies like sulphuretted hydrogen, hydrocyanic acid, &c., which act as strong poisons upon the latter, of “poisoning” the former also, i.e. of rendering it inactive. In the case of the catalytic action of water-vapour upon many processes of combustion already mentioned, a part of the effect is probably due to the circumstance, disclosed by numerous experiments, that the union of hydrogen and oxygen proceeds, between certain temperature limits at least, after the equation H2 + O2 = H2O2, that is, with the preliminary formation of hydrogen peroxide, which then breaks down into water and oxygen, and further, above all, to the fact that this substance results from oxygen and water at high temperatures with great velocity, though indeed only in small quantities.

The view now suggests itself, that, for example, in the combustion of carbon monoxide at moderately high temperatures, the reaction

advances with imperceptible speed, but that on the contrary the two stages

which together result in (I.), proceed rapidly even at moderate temperatures.

Temperature and Reaction-Velocity.—There are few natural constants which undergo so marked a change with temperature as those of the velocities of chemical changes. As a rule a rise of temperature of 10° causes a twofold or threefold rise of reaction-velocity.

If the reaction-coefficient k, in the sense of the equation derived above, viz. k = t-1 log {a / (a-x)}, be determined for the inversion of cane-sugar by an acid of given concentration, the following values are obtained:—

here a rise of temperature of only 30° suffices to raise the speed of inversion fifty times.

We possess no adequate explanation of this remarkable temperature influence; but some account of it is given by the molecular theory, according to which the energy of that motion of substances in homogeneous gaseous or liquid systems which constitutes heat increases with the temperature, and hence also the frequency of collision of the reacting substances. When we reflect that the velocity of motion of the molecules of gases, and in all probability those of liquids also, are proportional to the square root of the absolute temperature, and therefore rise by 32 only 1/6% per degree at room-temperature, and that we must assume the number of collisions proportional to the velocity of the molecules, we cannot regard the actually observed increase of reaction-velocity, which often amounts to 10 or 12% per degree, as exclusively due to the quickening of the molecular motion by heat. It is more probable that the increase of the kinetic energy of the atomic motions within the molecule itself is of significance here, as the rise of the specific heat of gases with temperature seems to show. The change of the reaction-coefficient k with temperature may be represented by the empirical equation log k = -AT-1 + B + CT, where A, B, C are positive constants. For low temperatures the influence of the last term is as a rule negligible, whilst for high temperatures the first term on the right side plays a vanishingly small part.

Definition of Chemical Affinity.—We have still to discuss the question of what is to be regarded as the measure of chemical affinity. Since we are not in a position to measure directly the intensity of chemical forces, the idea suggests itself to determine the strength of chemical affinity from the amount of the work which the corresponding reaction is able to do. To a certain extent the evolution of heat accompanying the reaction is a measure of this work, and attempts have been made to measure chemical affinities thermo-chemically, though it may be easily shown that this definition was not well chosen. For when, as is clearly most convenient, affinity is so defined that it determines under all circumstances the direction of chemical change, the above definition fails in so far as chemical processes often take place with absorption of heat, that is, contrary to affinities so defined. But even in those cases in which the course of the reaction at first proceeds in the sense of the evolution of heat, it is often observed that the reaction advances not to completion but to a certain equilibrium, or, in other words, stops before the evolution of heat is complete.

A definition free from this objection is supplied by the second law of thermodynamics, in accordance with which all processes must take place in so far as they are able to do external work. When therefore we identify chemical affinity with the maximum work which can be gained from the process in question, we reach such a definition that the direction of the process is under all conditions determined by the affinity. Further, this definition has proved serviceable in so far as the maximum work in many cases may be experimentally measured, and moreover it stands in a simple relation to the equilibrium constant K. Thermodynamics teaches that the maximum work A may be expressed as A = RT log K, when R denotes the gas-constant, T the absolute temperature. In this it is further assumed that both the molecular species produced as well as those that disappear are present in unit concentration. The simplest experimental method of directly determining chemical affinity consists in the measurement of electromotive force. The latter at once gives us the work which can be gained when the corresponding galvanic element supplies the electricity, and, since the chemical exchange of one gram-equivalent from Faraday’s law requires 96,540 coulombs, we obtain from the product of this number and the electromotive force the work per gram-equivalent in watt-seconds, and this quantity when multiplied by O.23872 is obtained in terms of the usual unit, the gram-calorie. Experience teaches that, especially when we have to deal with strong affinities, the affinity so determined is for the most part almost the same as the heat-evolution, whilst in the case in which only solid or liquid substances in the pure state take part in the reaction at low temperatures, heat-evolution and affinity appear to possess a practically identical value.

Hence it seems possible to calculate equilibria for low temperatures from heats of reaction, by the aid of the two equations

A = Q,   A = RT log K;

and since the change of A with temperature, as required by the principles of thermodynamics, follows from the specific heats of the reacting substances, it seems further possible to calculate chemical equilibria from heats of reaction and specific heats. The circumstance that chemical affinity and heat-evolution so nearly coincide at low temperatures may be derived from the hypothesis that chemical processes are the result of forces of attraction between the atoms of the different elements. If we may disregard the kinetic energy of the atoms, and this is legitimate for low temperatures, it follows that both heat-evolution and chemical affinity are merely equal to the decrease of the potential energy of the above-mentioned forces, and it is at once clear that the evolution of heat during a reaction between only pure solid or pure liquid substances possesses special importance.

More complicated is the case in which gases or dissolved substances take part. This is simplified if we first consider the mixing of two mutually chemically indifferent gases. Thermodynamics teaches that external work may be gained by the mere mixing of two such gases (see Diffusion), and these amounts of work, which assume very considerable proportions at high temperatures, naturally affect the value of the maximum work and so also of the affinity, in that they always come into play when gases or solutions react. While therefore we regard as chemical affinity in the strictest sense the decrease of potential energy of the forces acting between the atoms, it is clear that the quantities here involved exhibit the simplest relations under the experimental conditions just given, for when only substances in a pure state take part in a reaction, all mixing of different kinds of molecules is excluded; moreover, the circumstance that the respective substances are considered at very low temperatures reduces the quantities of energy absorbed as kinetic energy by their molecules to the smallest possible amount.

Chemical Resistance.—When we know the chemical affinity of a reaction, we are in a position to decide in which direction the process must advance, but, unless we know the reaction-velocity also, we can in many cases say nothing as to whether or not the reaction in question will progress with a practically inappreciable velocity so that apparent chemical indifference is the result. This question may be stated in the light of the law of mass-action briefly as follows:—From a knowledge of the chemical affinity we can calculate the equilibrium, i.e. the numerical value of the constant K = k / k′; but to be completely informed of the process we must know not only the ratio of the two velocity-constants k and k′, but also the separate absolute values of the same.

In many respects the following view is more comprehensive, though naturally in harmony with the one just expressed. Since the chemical equilibrium is periodically attained, it follows that, as in the case of the motion of a body or of the diffusion of a dissolved substance, it must be opposed by very great friction. In all these cases the velocity of the process at every instant is directly proportional to the driving-force and inversely proportional to the frictional resistance. We hence arrive at the result that an equation of the form

reaction-velocity = chemical force/chemical resistance

must also hold for chemical change; here we have an analogy with Ohm’s law. The “chemical force” at every instant may be calculated from the maximum work (affinity); as yet little is known about “chemical resistance,” but it is not improbable that it may be directly measured or theoretically deduced. The problem of the calculation of chemical reaction-velocity in absolute measure would then be solved; so far we possess indeed only a few general facts concerning the magnitude of chemical resistance. It is immeasurably small at ordinary temperatures for ion-reactions, and, on the other hand, fairly large for nearly all reactions in which carbon-bonds must be loosened (so-called “inertia of the carbon-bond”) and possesses very high values for most gas-reactions also. With rising temperature it always strongly diminishes; on the other hand, at very low temperatures its values are always enormous, and at the absolute zero of temperature may be infinitely great. Therefore at that temperature all reactions cease, since the denominator in the above expression assumes enormous values.

It is a very remarkable phenomenon that the chemical resistance is often small in the case of precisely those reactions in which the affinity is also small; to this circumstance is to be traced the fact that in many chemical changes the most stable condition is not at once reached, but is preceded by the formation 33 of more or less unstable intermediate products. Thus the unstable ozone is very often first formed on the evolution of oxygen, whilst in the reaction between oxygen and hydrogen water is often not at once formed, but first the unstable hydrogen peroxide as an intermediate product.

Let us now consider the chemical process in the light of the equation

reaction-velocity = chemical force/chemical resistance.

Thermodynamics shows that at very low temperatures, i.e. in the immediate vicinity of the absolute zero, there is no equilibrium, but every chemical process advances to completion in the one or the other direction. The chemical forces therefore act in the one direction towards complete consumption of the reacting substance. But since the chemical resistance is now immensely great, they can produce practically no appreciable result.

At higher temperatures the reaction always proceeds, at least in homogeneous systems, to a certain equilibrium, and as the chemical resistance now has finite values this equilibrium will always finally be reached after a longer or shorter time. Finally, at very high temperatures the chemical resistance is in every case very small, and the equilibrium is almost instantaneously reached; at the same time, the affinity of the reaction, as in the case of the mutual affinity between oxygen and hydrogen, may very strongly diminish, and we have then chemical indifference again, not because, as at low temperatures, the denominator of the previous expression becomes very great, but because the numerator now assumes vanishingly small values.

CHEMISTRY (formerly “chymistry”; Gr. χυμεία; for derivation see Alchemy), the natural science which has for its province the study of the composition of substances. In common with physics it includes the determination of properties or characters which serve to distinguish one substance from another, but while the physicist is concerned with properties possessed by all substances and with processes in which the molecules remain intact, the chemist is restricted to those processes in which the molecules undergo some change. For example, the physicist determines the density, elasticity, hardness, electrical and thermal conductivity, thermal expansion, &c.; the chemist, on the other hand, investigates changes in composition, such as may be effected by an electric current, by heat, or when two or more substances are mixed. A further differentiation of the provinces of chemistry and physics is shown by the classifications of matter. To the physicist matter is presented in three leading forms—solids, liquids and gases; and although further subdivisions have been rendered necessary with the growth of knowledge the same principle is retained, namely, a classification based on properties having no relation to composition. The fundamental chemical classification of matter, on the other hand, recognizes two groups of substances, namely, elements, which are substances not admitting of analysis into other substances, and compounds, which do admit of analysis into simpler substances and also of synthesis from simpler substances. Chemistry and physics, however, meet on common ground in a well-defined branch of science, named physical chemistry, which is primarily concerned with the correlation of physical properties and chemical composition, and, more generally, with the elucidation of natural phenomena on the molecular theory.

I. History

Although chemical actions must have been observed by man in the most remote times, and also utilized in such processes as the extraction of metals from their ores and in the arts of tanning and dyeing, there is no evidence to show that, beyond an unordered accumulation of facts, the early developments of these industries were attended by any real knowledge of the nature of the processes involved. All observations were the result of accident or chance, or possibly in some cases of experimental trial, but there is no record of a theory or even a general classification of the phenomena involved, although there is no doubt that the ancients had a fair knowledge of the properties and uses of the commoner substances. The origin of chemistry is intimately bound up with the arts which we have indicated; in this respect it is essentially an experimental science. A unifying principle of chemical and physical changes was provided by metaphysical conceptions of the structure of matter. We find the notion of “elements,” or primary qualities, which confer upon all species of matter their distinctive qualities by appropriate combination, and also the doctrine that Greek philosophy. matter is composed of minute discrete particles, prevailing in the Greek schools. These “elements,” however, had not the significance of the elements of to-day; they connoted physical appearances or qualities rather than chemical relations; and the atomic theory of the ancients is a speculation based upon metaphysical considerations, having, in its origin, nothing in common with the modern molecular theory, which was based upon experimentally observed properties of gases (see Element; Molecule).

Although such hypotheses could contribute nothing directly to the development of a science which laid especial claim to experimental investigations, yet indirectly they stimulated inquiry into the nature of the “essence” with which the four “elements” were associated. This quinta essentia had been speculated upon by the Greeks, some regarding it as immaterial or aethereal, and others as material; and a school of philosophers termed alchemists arose who attempted the isolation of this essence. The existence of a fundamental principle, unalterable and indestructible, prevailing alike through physical and chemical changes, was generally accepted. Any change which a substance may chance to undergo was simply due to the discarding or taking up of some proportion of the primary “elements” or qualities: of these coverings “water,” “air,” “earth” and “fire” were regarded as clinging most tenaciously to the essence, while “cold,” “heat,” “moistness” and “dryness” were more easily cast aside or assumed. Several origins have been Alchemy. suggested for the word alchemy, and there seems to have been some doubt as to the exact nature and import of the alchemical doctrines. According to M.P.E. Berthelot, “alchemy rested partly on the industrial processes of the ancient Egyptians, partly on the speculative theories of the Greek philosophers, and partly on the mystical reveries of the Gnostics and Alexandrians.” The search for this essence subsequently resolved itself into the desire to effect the transmutation of metals, more especially the base metals, into silver and gold. It seems that this secondary principle became the dominant idea in alchemy, and in this sense the word is used in Byzantine literature of the 4th century; Suidas, writing in 34 the 11th century, defines chemistry as the “preparation of silver and gold” (see Alchemy).

From the Alexandrians the science passed to the Arabs, who made discoveries and improved various methods of separating substances, and afterwards, from the 11th century, became seated in Europe, where the alchemical doctrines were assiduously studied until the 15th and 16th centuries. It is readily understood why men imbued with the authority of tradition should prosecute the search for a substance which would confer unlimited wealth upon the fortunate discoverer. Some alchemists honestly laboured to effect the transmutation and to discover the “philosopher’s stone,” and in many cases believed that they had achieved success, if we may rely upon writings assigned to them. The period, however, is one of literary forgeries; most of the MSS. are of uncertain date and authorship, and moreover are often so vague and mystical that they are of doubtful scientific value, beyond reflecting the tendencies of the age. The retaining of alchemists at various courts shows the high opinion which the doctrines had gained. It is really not extraordinary that Isaac Hollandus was able to indicate the method of the preparation of the “philosopher’s stone” from “adamic” or “virgin” earth, and its action when medicinally employed; that in the writings assigned to Roger Bacon, Raimon Lull, Basil Valentine and others are to be found the exact quantities of it to be used in transmutation; and that George Ripley, in the 15th century, had grounds for regarding its action as similar to that of a ferment.

In the view of some alchemists, the ultimate principles of matter were Aristotle’s four elements; the proximate constituents were a “sulphur” and a “mercury,” the father and mother of the metals; gold was supposed to have attained to the perfection of its nature by passing in succession through the forms of lead, brass and silver; gold and silver were held to contain very pure red sulphur and white quicksilver, whereas in the other metals these materials were coarser and of a different colour. From an analogy instituted between the healthy human being and gold, the most perfect of the metals, silver, mercury, copper, iron, lead and tin, were regarded in the light of lepers that required to be healed.

Notwithstanding the false idea which prompted the researches of the alchemists, many advances were made in descriptive chemistry, the metals and their salts receiving much Iatrochemistry. attention, and several of our important acids being discovered. Towards the 16th century the failure of the alchemists to achieve their cherished purpose, and the general increase of medical knowledge, caused attention to be given to the utilization of chemical preparations as medicines. As early as the 15th century the alchemist Basil Valentine had suggested this application, but the great exponent of this doctrine was Paracelsus, who set up a new definition: “The true use of chemistry is not to make gold but to prepare medicines.” This relation of chemistry to medicine prevailed until the 17th century, and what in the history of chemistry is termed the iatrochemical period (see Medicine) was mainly fruitful in increasing the knowledge of compounds; the contributions to chemical theory are of little value, the most important controversies ranging over the nature of the “elements,” which were generally akin to those of Aristotle, modified so as to be more in accord with current observations. At the same time, however, there were many who, opposed to the Paracelsian definition of chemistry, still laboured at the problem of the alchemists, while others gave much attention to the chemical industries. Metallurgical operations, such as smelting, roasting and refining, were scientifically investigated, and in some degree explained, by Georg Agricola and Carlo Biringuiccio; ceramics was studied by Bernard Palissy, who is also to be remembered as an early worker in agricultural chemistry, having made experiments on the effect of manures on soils and crops; while general technical chemistry was enriched by Johann Rudolf Glauber.1

The second half of the 17th century witnessed remarkable transitions and developments in all branches of natural science, and the facts accumulated by preceding generations Boyle. during their generally unordered researches were replaced by a co-ordination of experiment and deduction. From the mazy and incoherent alchemical and iatrochemical doctrines, the former based on false conceptions of matter, the latter on erroneous views of life processes and physiology, a new science arose—the study of the composition of substances. The formulation of this definition of chemistry was due to Robert Boyle. In his Sceptical Chemist (1662) he freely criticized the prevailing scientific views and methods, with the object of showing that true knowledge could only be gained by the logical application of the principles of experiment and deduction. Boyle’s masterly exposition of this method is his most important contribution to scientific progress. At the same time he clarified the conception of elements and compounds, rejecting the older notions, the four elements of the “vulgar Peripateticks” and the three principles of the “vulgar Stagyrists,” and defining an element as a substance incapable of decomposition, and a compound as composed of two or more elements. He explained chemical combination on the hypotheses that matter consisted of minute corpuscles, that by the coalescence of corpuscles of different substances distinctly new corpuscles of a compound were formed, and that each corpuscle had a certain affinity for other corpuscles.

Although Boyle practised the methods which he expounded, he was unable to gain general acceptance of his doctrine of elements; and, strangely enough, the theory which next dominated chemical thought was an alchemical Phlogistic theory. invention, and lacked the lucidity and perspicuity of Boyle’s views. This theory, named the phlogistic theory, was primarily based upon certain experiments on combustion and calcination, and in effect reduced the number of the alchemical principles, while setting up a new one, a principle of combustibility, named phlogiston (from φλοιστός, burnt). Much discussion had centred about fire or the “igneous principle.” On the one hand, it had been held that when a substance was burned or calcined, it combined with an “air”; on the other hand, the operation was supposed to be attended by the destruction or loss of the igneous principle. Georg Ernst Stahl, following in some measure the views held by Johann Joachim Becher, as, for instance, that all combustibles contain a “sulphur” (which notion is itself of older date than Becher’s terra pinguis), regarded all substances as capable of resolution into two components, the inflammable principle phlogiston, and another element—“water,” “acid” or “earth.” The violence or completeness of combustion was proportional to the amount of phlogiston present. Combustion meant the liberation of phlogiston. Metals on calcination gave calces from which the metals could be recovered by adding phlogiston, and experiment showed that this could generally be effected by the action of coal or carbon, which was therefore regarded as practically pure phlogiston; the other constituent being regarded as an acid. At the hands of Stahl and his school, the phlogistic theory, by exhibiting a fundamental similarity between all processes of combustion and by its remarkable flexibility, came to be a general theory of chemical action. The objections of the antiphlogistonists, such as the fact that calces weigh more than the original metals instead of less as the theory suggests, were answered by postulating that phlogiston was a principle of levity, or even completely ignored as an accident, the change of qualities being regarded as the only matter of importance. It is remarkable that this theory should have gained the esteem of the notable chemists who flourished in the 18th century. Henry Cavendish, a careful and accurate experimenter, was a phlogistonist, as were J. Black, K. W. Scheele, A. S. Marggraf, J. Priestley and many others who might be mentioned.

35

Descriptive chemistry was now assuming considerable proportions; the experimental inquiries suggested by Boyle were being assiduously developed; and a wealth of observations Lavoisier. was being accumulated, for the explanation of which the resources of the dominant theory were sorely taxed. To quote Antoine Laurent Lavoisier, “... chemists have turned phlogiston into a vague principle, ... which consequently adapts itself to all the explanations for which it may be required. Sometimes this principle has weight, and sometimes it has not; sometimes it is free fire and sometimes it is fire combined with the earthy element; sometimes it passes through the pores of vessels, sometimes these are impervious to it; it explains both causticity and non-causticity, transparency and opacity, colours and their absence; it is a veritable Proteus changing in form at each instant.” Lavoisier may be justly regarded as the founder of modern or quantitative chemistry. First and foremost, he demanded that the balance must be used in all investigations into chemical changes. He established as fundamental that combustion and calcination were attended by an increase of weight, and concluded, as did Jean Rey and John Mayow in the 17th century, that the increase was due to the combination of the metal with the air. The problem could obviously be completely solved only when the composition of the air, and the parts played by its components, had been determined. At all times the air had received attention, especially since van Helmont made his far-reaching investigations on gases. Mayow had suggested the existence of two components, a spiritus nitroaerus which supported combustion, and a spiritus nitri acidi which extinguished fire; J. Priestley and K. W. Scheele, although they isolated oxygen, were fogged by the phlogistic tenets; and H. Cavendish, who had isolated the nitrogen of the atmosphere, had failed to decide conclusively what had really happened to the air which disappeared during combustion.

Lavoisier adequately recognized and acknowledged how much he owed to the researches of others; to himself is due the co-ordination of these researches, and the welding of his results into a doctrine to which the phlogistic theory ultimately succumbed. He burned phosphorus in air standing over mercury, and showed that (1) there was a limit to the amount of phosphorus which could be burned in the confined air, (2) that when no more phosphorus could be burned, one-fifth of the air had disappeared, (3) that the weight of the air lost was nearly equal to the difference in the weights of the white solid produced and the phosphorus burned, (4) that the density of the residual air was less than that of ordinary air. The same results were obtained with lead and tin; and a more elaborate repetition indubitably established their correctness. He also showed that on heating mercury calx alone an “air” was liberated which differed from other “airs,” and was slightly heavier than ordinary air; moreover, the weight of the “air” set free from a given weight of the calx was equal to the weight taken up in forming the calx from mercury, and if the calx be heated with charcoal, the metal was recovered and a gas named “fixed air,” the modern carbon dioxide, was formed. The former experiment had been performed by Scheele and Priestley, who had named the gas “phlogisticated air”; Lavoisier subsequently named it oxygen, regarding it as the “acid producer” (ὀξύς, sour). The theory advocated by Lavoisier came to displace the phlogistic conception; but at first its acceptance was slow. Chemical literature was full of the phlogistic modes of expression—oxygen was “dephlogisticated air,” nitrogen “phlogisticated air,” &c.—and this tended to retard its promotion. Yet really the transition from the one theory to the other was simple, it being only necessary to change the “addition or loss of phlogiston” into the “loss or addition of oxygen.” By his insistence upon the use of the balance as a quantitative check upon the masses involved in all chemical reactions, Lavoisier was enabled to establish by his own investigations and the results achieved by others the principle now known as the “conservation of mass.” Matter can neither be created nor destroyed; however a chemical system be changed, the weights before and after are equal.2 To him is also due a rigorous examination of the nature of elements and compounds; he held the same views that were laid down by Boyle, and with the same prophetic foresight predicted that some of the elements which he himself accepted might be eventually found to be compounds.

It is unnecessary in this place to recapitulate the many results which had accumulated by the end of the 18th century, or to discuss the labours and theories of individual workers since these receive attention under biographical headings; in this article only the salient features in the history of our science can be treated. The beginning of the 19th century was attended by far-reaching discoveries in the nature of the composition of compounds. Investigations proceeded in two directions:—(1) the nature of chemical affinity, (2) the laws Chemical Affinity. of chemical combination. The first question has not yet been solved, although it has been speculated upon from the earliest times. The alchemists explained chemical action by means of such phrases as “like attracts like,” substances being said to combine when one “loved” the other, and the reverse when it “hated” it. Boyle rejected this terminology, which was only strictly applicable to intelligent beings; and he used the word “affinity” as had been previously done by Stahl and others. The modern sense of the word, viz. the force which holds chemically dissimilar substances together (and also similar substances as is seen in di-, tri-, and poly-atomic molecules), was introduced by Hermann Boerhaave, and made more precise by Sir Isaac Newton. The laws of chemical combination were solved, in a measure, by John Dalton, and the solution expressed as Dalton’s “atomic theory.” Lavoisier appears to have assumed that the composition of every chemical compound was constant, and the same opinion was the basis of much experimental inquiry at the hands of Joseph Louis Proust during 1801 to 1809, who vigorously combated the doctrine of Claude Louis Berthollet (Essai de statique chimique, 1803), viz. that fixed proportions of elements and compounds combine only under exceptional conditions, the general rule being that the composition of a compound may vary continuously between certain limits.3

This controversy was unfinished when Dalton published the first part of his New System of Chemical Philosophy in 1808, although the per saltum theory was the most popular. Dalton. Led thereto by speculations on gases, Dalton assumed that matter was composed of atoms, that in the elements the atoms were simple, and in compounds complex, being composed of elementary atoms. Dalton furthermore perceived that the same two elements or substances may combine in different proportions, and showed that these proportions had always a simple ratio to one another. This is the “law of multiple proportions.” He laid down the following arbitrary rules for determining the number of atoms in a compound:—if only one compound of two elements exists, it is a binary compound and its atom is composed of one atom of each element; if two compounds exist one is binary (say A + B) and the other ternary (say A + 2B); if three, then one is binary and the others may be ternary (A + 2B, and 2A + B), and so on. More important is his deduction of equivalent weights, i.e. the relative weights of atoms. He took hydrogen, the lightest substance known, to be the standard. From analyses of water, which he regarded as composed of one atom of hydrogen and one of oxygen, he 36 deduced the relative weight of the oxygen atom to be 6.5; from marsh gas and olefiant gas he deduced carbon = 5, there being one atom of carbon and two of hydrogen in the former and one atom of hydrogen to one of carbon in the latter; nitrogen had an equivalent of 5, and so on.4

The value of Dalton’s generalizations can hardly be overestimated, notwithstanding the fact that in several cases they needed correction. The first step in this direction was effected by the co-ordination of Gay Lussac’s observations on the combining volumes of gases. He discovered that gases always combined in volumes having simple ratios, and that the volume of the product had a simple ratio to the volumes of the reacting gases. For example, one volume of oxygen combined with two of hydrogen to form two volumes of steam, three volumes of hydrogen combined with one of nitrogen to give two volumes of ammonia, one volume of hydrogen combined with one of chlorine to give two volumes of hydrochloric acid. An immediate inference was that the Daltonian “atom” must have parts which enter into combination with parts of other atoms; in other words, there must exist two orders of particles, viz. (1) particles derived by limiting mechanical subdivision, the modern molecule, and (2) particles derived from the first class by chemical subdivision, i.e. particles which are incapable of existing alone, but may exist in combination. Additional evidence as to the structure of the molecule was discussed by Avogadro in 1811, and by Ampere in 1814. From the gas-laws of Boyle and J.A.C. Charles—viz. equal changes in temperature and pressure occasion equal changes in equal volumes of all gases and vapours—Avogadro deduced the law:—Under the same conditions of temperature and pressure, equal volumes of gases contain equal numbers of molecules; and he showed that the relative weights of the molecules are determined as the ratios of the weights of equal volumes, or densities. He established the existence of molecules and atoms as we have defined above, and stated that the number of atoms in the molecule is generally 2, but may be 4, 8, &c. We cannot tell whether his choice of the powers of 2 is accident or design.

Notwithstanding Avogadro’s perspicuous investigation, and a similar exposition of the atom and molecule by A. M. Ampere, the views therein expressed were ignored both by Berzelius. their own and the succeeding generation. In place of the relative molecular weights, attention was concentrated on relative atomic or equivalent weights. This may be due in some measure to the small number of gaseous and easily volatile substances then known, to the attention which the study of the organic compounds received, and especially to the energetic investigations of J. J. Berzelius, who, fired with enthusiasm by the original theory of Dalton and the law of multiple proportions, determined the equivalents of combining ratios of many elements in an enormous number of compounds.5 He prosecuted his labours in this field for thirty years; as proof of his industry it may be mentioned that as early as 1818 he had determined the combining ratios of about two thousand simple and compound substances.

In the development of the atomic theory and the deduction of the atomic weights of elements and the formulae of compounds, Dalton’s arbitrary rules failed to find complete acceptance. Extension of the atomic theory. Berzelius objected to the hypothesis that if two elements form only one compound, then the atoms combine one and one; and although he agreed with the adoption of simple rules as a first attempt at representing a compound, he availed himself of other data in order to gain further information as to the structure of compounds. For example, at first he represented ferrous and ferric oxides by the formulae FeO2, FeO3, and by the analogy of zinc and other basic oxides he regarded these substances as constituted similarly to FeO2, and the acidic oxides alumina and chromium oxide as similar to FeO3. He found, however, that chromic acid, which he had represented as CrO6, neutralized a base containing 1/3 the 37 quantity of oxygen. He inferred that chromic acid must contain only three atoms of oxygen, as did sulphuric acid SO3; consequently chromic oxide, which contains half the amount of oxygen, must be Cr2O3, and hence ferric oxide must be Fe2O3. The basic oxides must have the general formula MO. To these results he was aided by the law of isomorphism formulated by E. Mitscherlich in 1820; and he confirmed his conclusions by showing the agreement with the law of atomic heat formulated by Dulong and Petit in 1819.

While successfully investigating the solid elements and their compounds gravimetrically, Berzelius was guilty of several inconsistencies in his views on gases. He denied that gaseous atoms could have parts, although compound gases could. This attitude was due to his adherence to the “dualistic theory” of the structure of substances, which he deduced from electrochemical researches. From the behaviour of substances on electrolysis (q.v.) he assumed that all substances had two components, one bearing a negative charge, the other a positive charge. Combination was associated with the coalescence of these charges, and the nature of the resulting compound showed the nature of the residual electricity. For example, positive iron combined with negative oxygen to form positive ferrous oxide; positive sulphur combined with negative oxygen to form negative sulphuric acid; positive ferrous oxide combined with negative sulphuric acid to form neutral ferrous sulphate. Berzelius elevated this theory to an important position in the history of our science. He recognized that if an elementary atom had parts, his theory demanded that these parts should carry different electric charges when they entered into reaction, and the products of the reaction should vary according as a positive or negative atom entered into combination. For instance if the reaction 2H2 + O2 = H2O + H2O be true, the molecules of water should be different, for a negative oxygen atom would combine in one case, and a positive oxygen atom in the other. Hence the gaseous atoms of hydrogen and oxygen could not have parts. A second inconsistency was presented when he was compelled by the researches of Dumas to admit Avogadro’s hypothesis; but here he would only accept it for the elementary gases, and denied it for other substances. It is to be noticed that J.B. Dumas did not adopt the best methods for emphasizing his discoveries. His terminology was vague and provoked caustic criticism from Berzelius; he assumed that all molecules contained two atoms, and consequently the atomic weights deduced from vapour density determinations of sulphur, mercury, arsenic, and phosphorus were quite different from those established by gravimetric and other methods.

Chemists gradually tired of the notion of atomic weights on account of the uncertainty which surrounded them; and the suggestion made by W.H. Wollaston as early as 1814 to deal only with “equivalents,” i.e. the amount of an element which can combine with or replace unit weight of hydrogen, came into favour, being adopted by L. Gmelin in his famous text-book.

Simultaneously with this discussion of the atom and molecule, great controversy was ranging over the constitution of compounds, more particularly over the carbon or organic Atomic and molecular weights. compounds. This subject is discussed in section IV., Organic Chemistry.The gradual accumulation of data referring to organic compounds brought in its train a revival of the discussion of atoms and molecules. A. Laurent and C.F. Gerhardt attempted a solution by investigating chemical reactions. They assumed the atom to be the smallest part of matter which can exist in combination, and the molecule to be the smallest part which can enter into a chemical reaction. Gerhardt found that reactions could be best followed if one assumed the molecular weight of an element or compound to be that weight which occupied the same volume as two unit weights of hydrogen, and this assumption led him to double the equivalents accepted by Gmelin, making H = 1, O = 16, and C = 12, thereby agreeing with Berzelius, and also to halve the values given by Berzelius to many metals. Laurent generally agreed, except when the theory compelled the adoption of formulae containing fractions of atoms; in such cases he regarded the molecular weight as the weight occupying a volume equal to four unit weights of hydrogen. The bases upon which Gerhardt and Laurent founded their views were not sufficiently well grounded to lead to the acceptance of their results; Gerhardt himself returned to Gmelin’s equivalents in his Lehrbuch der Chemie (1853) as they were in such general use.

In 1860 there prevailed such a confusion of hypotheses as to the atom and molecule that a conference was held at Karlsruhe to discuss the situation. At the conclusion of the sitting, Lothar Meyer obtained a paper written by Stanislas Cannizzaro in 1858 wherein was found the final link required for the determination of atomic weights. This link was the full extension of Avogadro’s theory to all substances, Cannizzaro showing that chemical reactions in themselves would not suffice. He chose as his unit of reference the weight of an atom of hydrogen, i.e. the weight contained in a molecule of hydrochloric acid, thus differing from Avogadro who chose the weight of a hydrogen molecule. From a study of the free elements Cannizzaro showed that an element may have more than one molecular weight; for example, the molecular weight of sulphur varied with the temperature. And from the study of compounds he showed that each element occurred in a definite weight or in some multiple of this weight. He called this proportion the “atom,” since it invariably enters compounds without division, and the weight of this atom is the atomic weight. This generalization was of great value inasmuch as it permitted the deduction of the atomic weight of a non-gasifiable element from a study of the densities of its gasifiable compounds.

From the results obtained by Laurent and Gerhardt and their predecessors it immediately followed that, while an element could have but one atomic weight, it could have several equivalent weights. From a detailed study of organic compounds Gerhardt had promulgated a “theory of types” which represented a fusion of the older radical and type theories. This theory brought together, as it were, the most varied compounds, and stimulated inquiry into many fields. According to this theory, an element in a compound had a definite saturation capacity, an idea very old in itself, being framed in the law of multiple Valency. proportions. These saturation capacities were assiduously studied by Sir Edward Frankland, who from the investigation, not of simple inorganic compounds, but of the organo-metallic derivatives, determined the kernel of the theory of valency. Frankland showed that any particular element preferentially combined with a definite number (which might vary between certain limits) of other atoms; for example, some atoms always combined with one atom of oxygen, some with two, while with others two atoms entered into combination with one of oxygen. If an element or radical combined with one atom of hydrogen, it was termed monovalent; if with two (or with one atom of oxygen, which is equivalent to two atoms of hydrogen) it was divalent, and so on. The same views were expressed by Cannizzaro, and also by A.W. von Hofmann, who materially helped the acceptance of the doctrine by the lucid exposition in his Introduction to Modern Chemistry, 1865.

The recognition of the quadrivalency of carbon by A. Kekulé was the forerunner of his celebrated benzene theory in particular, and of the universal application of structural formulae to the representation of the most complex organic compounds equally lucidly as the representation of the simplest salts. Alexander Butlerow named the “structure theory,” and contributed much to the development of the subject. He defined structure “as the manner of the mutual linking of the atoms in the molecule,” but denied that any such structure could give information as to the orientation of the atoms in space. He regarded the chemical properties of a substance as due to (1) the chemical atoms composing it, and (2) the structure, and he asserted that while different compounds might have the same components (isomerism), yet only one compound could have a particular structure. Identity in properties necessitated identity in structure.

While the principle of varying valency laid down by Frankland is still retained, Butlerow’s view that structure had no spatial significance has been modified. The researches of L. Pasteur, 38 J.A. Le Bel, J. Wislicenus, van’t Hoff and others showed that substances having the same graphic formulae vary in properties and reactions, and consequently the formulae need modification in order to exhibit these differences. Such isomerism, named stereoisomerism (q.v.), has been assiduously developed during recent years; it prevails among many different classes of organic compounds and many examples have been found in inorganic chemistry.

The theory of valency as a means of showing similarity of properties and relative composition became a dominant feature of chemical theory, the older hypotheses of types, radicals, &c. being more or less discarded. We have seen how its Periodic law. utilization in the “structure theory” permitted great clarification, and attempts were not wanting for the deduction of analogies or a periodicity between elements. Frankland had recognized the analogies existing between the chemical properties of nitrogen, phosphorus, arsenic and antimony, noting that they act as tri- or penta-valent. Carbon was joined with silicon, zirconium and titanium, while boron, being trivalent, was relegated to another group. A general classification of elements, however, was not realized by Frankland, nor even by Odling, who had also investigated the question from the valency standpoint. The solution came about by arranging the elements in the order of their atomic weights, tempering the arrangement with the results deduced from the theory of valencies and experimental observations. Many chemists contributed to the establishment of such a periodicity, the greatest advances being made by John Newlands in England, Lothar Meyer in Germany, and D.J. Mendeléeff in St Petersburg. For the development of this classification see Element.

In the above sketch we have briefly treated the history of the main tendencies of our science from the earliest times to the establishment of the modern laws and principles. We Summary. have seen that the science took its origin in the arts practised by the Egyptians, and, having come under the influence of philosophers, it chose for its purpose the isolation of the quinta essentia, and subsequently the “art of making gold and silver.” This spirit gave way to the physicians, who regarded “chemistry as the art of preparing medicines,” a denotation which in turn succumbed to the arguments of Boyle, who regarded it as the “science of the composition of substances,” a definition which adequately fits the science to-day. We have seen how his classification of substances into elements and compounds, and the definitions which he assigned to these species, have similarly been retained; and how Lavoisier established the law of the “conservation of mass,” overthrew the prevailing phlogistic theory, and became the founder of modern chemistry by the overwhelming importance which he gave to the use of the balance. The development of the atomic theory and its concomitants—the laws of chemical combination and the notion of atoms and equivalents—at the hands of Dalton and Berzelius, the extension to the modern theory of the atom and molecule, and to atomic and molecular weights by Avogadro, Ampère, Dumas, Laurent, Gerhardt, Cannizzaro and others, have been noted. The structure of the molecule, which mainly followed investigations in organic compounds, Frankland’s conception of valency, and finally the periodic law, have also been shown in their chronological order. The principles outlined above constitute the foundations of our science; and although it may happen that experiments may be made with which they appear to be not in complete agreement, yet in general they constitute a body of working hypotheses of inestimable value.

Chemical Education.—It is remarkable that systematic instruction in the theory and practice of chemistry only received earnest attention in our academic institutions during the opening decades of the 19th century. Although for a long time lecturers and professors had been attached to universities, generally their duties had also included the study of physics, mineralogy and other subjects, with the result that chemistry received scanty encouragement. Of practical instruction there was none other than that to be gained in a few private laboratories and in the shops of apothecaries. The necessity for experimental demonstration and practical instruction, in addition to academic lectures, appears to have been urged by the French chemists L.N. Vauquelin, Gay Lussac, Thénard, and more especially by A.F. Fourcroy and G.F. Rouelle, while in England Humphry Davy expounded the same idea in the experimental demonstrations which gave his lectures their brilliant charm. But the real founder of systematic instruction in our science was Justus von Liebig, who, having accepted the professorship at Giessen in 1824, made his chemical laboratory and course of instruction the model of all others. He emphasized that the practical training should include (1) the qualitative and quantitative analysis of mixtures, (2) the preparation of substances according to established methods, (3) original research—a course which has been generally adopted. The pattern set by Liebig at Giessen was adopted by F. Wöhler at Göttingen in 1836, by R.W. Bunsen at Marburg in 1840, and by O.L. Erdmann at Leipzig in 1843; and during the ’fifties and ’sixties many other laboratories were founded. A new era followed the erection of the laboratories at Bonn and Berlin according to the plans of A.W. von Hofmann in 1867, and of that at Leipzig, designed by Kolbe in 1868. We may also mention the famous laboratory at Munich designed by A. von Baeyer in 1875.

In Great Britain the first public laboratory appears to have been opened in 1817 by Thomas Thomson at Glasgow. But the first important step in providing means whereby students could systematically study chemistry was the foundation of the College of Chemistry in 1845. This institution was taken over by the Government in 1853, becoming the Royal College of Chemistry, and incorporated with the Royal School of Mines; in 1881 the names were changed to the Normal School of Science and Royal School of Mines, and again in 1890 to the Royal College of Science. In 1907 it was incorporated in the Imperial College of Science and Technology. Under A.W. von Hofmann, who designed the laboratories and accepted the professorship in 1845 at the instigation of Prince Albert, and under his successor (in 1864) Sir Edward Frankland, this institution became one of the most important centres of chemical instruction. Oxford and Cambridge sadly neglected the erection of convenient laboratories for many years, and consequently we find technical schools and other universities having a far better equipment and offering greater facilities. In the provinces Victoria University at Manchester exercised the greater impetus, numbering among its professors Sir W.H. Perkin and Sir Henry Roscoe.

In America public laboratory instruction was first instituted at Yale College during the professorship of Benjamin Silliman. To the great progress made in recent years F.W. Clarke, W. Gibbs, E.W. Morley, Ira Remsen, and T.W. Richards have especially contributed.

In France the subject was almost entirely neglected until late in the 19th century. The few laboratories existing in the opening decades were ill-fitted, and the exorbitant fees constituted a serious bar to general instruction, for these institutions received little government support. In 1869 A. Wurtz reported the existence of only one efficient laboratory in France, namely the École Normale Supérieure, under the direction of H. Sainte Claire Deville. During recent years chemistry has become one of the most important subjects in the curriculum of technical schools and universities, and at the present time no general educational institution is complete until it has its full equipment of laboratories and lecture theatres.

II. General Principles

The substances with which the chemist has to deal admit of classification into elements and compounds. Of the former about eighty may be regarded as well characterized, although many more have been described.

Elements.—The following table gives the names, symbols and atomic weights of the perfectly characterized elements:—

International Atomic Weights, 1910.

The elements are usually divided into two classes, the metallic and the non-metallic elements; the following are classed as non-metals, and the remainder as metals:—

Of these hydrogen, chlorine, fluorine, oxygen, nitrogen, argon, neon, krypton, xenon and helium are gases, bromine is a liquid, and the remainder are solids. All the metals are solids at ordinary temperatures with the exception of mercury, which is liquid. The metals are mostly bodies of high specific gravity; they exhibit, when polished, a peculiar brilliancy or metallic lustre, and they are good conductors of heat and electricity; the non-metals, on the other hand, are mostly bodies of low specific gravity, and bad conductors of heat and electricity, and do not exhibit metallic lustre. The non-metallic elements are also sometimes termed metalloids, but this appellation, which signifies metal-like substances (Gr. εἰδος, like), strictly belongs to certain elements which do not possess the properties of the true metals, although they more closely resemble them than the non-metals in many respects; thus, selenium and tellurium, which are closely allied to sulphur in their chemical properties, although bad conductors of heat and electricity, exhibit metallic lustre and have relatively high specific gravities. But when the properties of the elements are carefully contrasted together it is found that no strict line of demarcation can be drawn dividing them into two classes; and if they are arranged in a series, those which are most closely allied in properties being placed next to each other, it is observed that there is a more or less regular alteration in properties from term to term in the series.

When binary compounds, or compounds of two elements, are decomposed by an electric current, the two elements make their appearance at opposite poles. Those elements which are disengaged at the negative pole are termed electro-positive, or positive, or basylous elements, whilst those disengaged at the positive pole are termed electro-negative, or negative, or chlorous elements. But the difference between these two classes of elements is one of degree only, and they gradually merge into each other; moreover the electric relations of elements are not absolute, but vary according to the state of combination in which they exist, so that it is just as impossible to divide the elements into two classes according to this property as it is to separate them into two distinct classes of metals and non-metals. The following, however, are negative towards the remaining elements which are more or less positive:—Fluorine, chlorine, bromine, iodine, oxygen, sulphur, selenium, tellurium.

The metals may be arranged in a series according to their power of displacing one another in salt solutions, thus Cs, Rb, K, Na, Mg, Al, Mn, Zn, Cd, Tl, Fe, Co, Ni, Sn, Pb, (H), Sb, Bi, As, Cu, Hg, Ag, Pd, Pt, Au.

Elements which readily enter into reaction with each other, and which develop a large amount of heat on combination, are said to have a powerful affinity for each other. The tendency of positive elements to unite with positive elements, or of negative elements to unite with negative elements, is much less than that of positive elements to unite with negative elements, and the greater the difference in properties between two elements the more powerful is their affinity for each other. Thus, the affinity of hydrogen and oxygen for each other is extremely powerful, much heat being developed by the combination of these two elements; when binary compounds of oxygen are decomposed by the electric current, the oxygen invariably appears at the positive pole, being negative to all other elements, but the hydrogen of hydrogen compounds is always disengaged at the negative pole. Hydrogen and oxygen are, therefore, of very opposite natures, and this is well illustrated by the circumstance that oxygen combines, with very few exceptions, with all the remaining elements, whilst compounds of only a limited number with hydrogen have been obtained.

Compounds.—A chemical compound contains two or more 40 elements; consequently it should be possible to analyse it, i.e. separate it into its components, or to synthesize it, i.e. build it up from its components. In general, a compound has properties markedly different from those of the elements of which it is composed.

Laws of Chemical Combination.—A molecule may be defined as the smallest part of a substance which can exist alone; an atom as the smallest part of a substance which can exist in combination. The molecule of every compound must obviously contain at least two atoms, and generally the molecules of the elements are also polyatomic, the elements with monatomic molecules (at moderate temperatures) being mercury and the gases of the argon group. The laws of chemical combination are as follows:—

1. Law of Definite Proportions.—The same compound always contains the same elements combined together in the same mass proportion. Silver chloride, for example, in whatever manner it may be prepared, invariably consists of chlorine and silver in the proportions by weight of 35.45 parts of the former and 107.93 of the latter.

2. Law of Multiple Proportions.—When the same two elements combine together to form more than one compound, the different masses of one of the elements which unite with a constant mass of the other, bear a simple ratio to one another. Thus, 1 part by weight of hydrogen unites with 8 parts by weight of oxygen, forming water, and with 16 or 8 × 2 parts of oxygen, forming hydrogen peroxide. Again, in nitrous oxide we have a compound of 8 parts by weight of oxygen and 14 of nitrogen; in nitric oxide a compound of 16 or 8 × 2 parts of oxygen and 14 of nitrogen; in nitrous anhydride a compound of 24 or 8 × 3 parts of oxygen and 14 of nitrogen; in nitric peroxide a compound of 32 or 8 × 4 parts of oxygen and 14 of nitrogen; and lastly, in nitric anhydride a compound of 40 or 8 × 5 parts of oxygen and 14 of nitrogen.

3. Law of Reciprocal Proportions.—The masses of different elements which combine separately with one and the same mass of another element, are either the same as, or simple multiples of, the masses of these different elements which combine with each other. For instance, 35.45 parts of chlorine and 79.96 parts of bromine combine with 107.93 parts of silver; and when chlorine and bromine unite it is in the proportion of 35.45 parts of the former to 79.96 parts of the latter. Iodine unites with silver in the proportion of 126.97 parts to 107.93 parts of the latter, but it combines with chlorine in two proportions, viz. in the proportion of 126.97 parts either to 35.45 or to three times 35.45 parts of chlorine.

There is a fourth law of chemical combination which only applies to gases. This law states that:—gases combine with one another in simple proportions by volume, and the volume of the product (if gaseous) has a simple ratio to the volumes of the original mixtures; in other words, the densities of gases are simply related to their combining weights.

Nomenclature.—If a compound contains two atoms it is termed a binary compound, if three a ternary, if four a quaternary, and so on. Its systematic name is formed by replacing the last syllable of the electro-negative element by ide and prefixing the name of the other element. For example, compounds of oxygen are oxides, of chlorine, chlorides, and so on. If more than one compound be formed from the same two elements, the difference is shown by prefixing such words as mono-, di-, tri-, sesqui-, per-, sub-, &c., to the last part of the name, or the suffixes -ous and -ic may be appended to the name of the first element. For example take the oxides of nitrogen, N2O, NO, N2O3, NO2, N2O5; these are known respectively as nitrous oxide, nitric oxide, nitrogen trioxide, nitrogen peroxide and nitrogen pentoxide. The affixes -ous and sub- refer to the compounds containing more of the positive element, -ic and per- to those containing less.

An acid (q.v.) is a compound of hydrogen, which element can be replaced by metals, the hydrogen being liberated, giving substances named salts. An alkali or base is a substance which neutralizes an acid with the production of salts but with no evolution of hydrogen. A base may be regarded as water in which part of the hydrogen is replaced by a metal, or by a radical which behaves as a metal. (The term radical is given to a group of atoms which persist in chemical changes, behaving as if the group were an element; the commonest is the ammonium group, NH4, which forms salts similar to the salts of sodium and potassium.) If the acid contains no oxygen it is a hydracid, and its systematic name is formed from the prefix hydro- and the name of the other element or radical, the last syllable of which has been replaced by the termination -ic. For example, the acid formed by hydrogen and chlorine is termed hydrochloric acid (and sometimes hydrogen chloride). If an acid contains oxygen it is termed an oxyacid. The nomenclature of acids follows the same general lines as that for binary compounds. If one acid be known its name is formed by the termination -ic, e.g. carbonic acid; if two, the one containing the less amount of oxygen takes the termination -ous and the other the termination -ic, e.g. nitrous acid, HNO2, nitric acid, HNO3. If more than two be known, the one inferior in oxygen content has the prefix hypo- and the termination -ous, and the one superior in oxygen content has the prefix per- and the termination -ic. This is illustrated in the four oxyacids of chlorine, HClO, HClO2, HClO3, HClO4, which have the names hypochlorous, chlorous, chloric and perchloric acids. An acid is said to be monobasic, dibasic, tribasic, &c., according to the number of replaceable hydrogen atoms; thus HNO3 is monobasic, sulphuric acid H2SO4 dibasic, phosphoric acid H3PO4 tribasic.

An acid terminating in -ous forms a salt ending in -ite, and an oxyacid ending in -ic forms a salt ending in -ate. Thus the chlorine oxyacids enumerated above form salts named respectively hypochlorites, chlorites, chlorates and perchlorates. Salts formed from hydracids terminate in -ide, following the rule for binary compounds. An acid salt is one in which the whole amount of hydrogen has not been replaced by metal; a normal salt is one in which all the hydrogen has been replaced; and a basic salt is one in which part of the acid of the normal salt has been replaced by oxygen.

Chemical Formulae.—Opposite the name of each element in the second column of the above table, the symbol is given which is always employed to represent it. This symbol, however, not only represents the particular element, but a certain definite quantity of it. Thus, the letter H always stands for 1 atom or 1 part by weight of hydrogen, the letter N for 1 atom or 14 parts of nitrogen, and the symbol Cl for 1 atom or 35.5 parts of chlorine.8 Compounds are in like manner represented by writing the symbols of their constituent elements side by side, and if more than one atom of each element be present, the number is indicated by a numeral placed on the right of the symbol of the element either below or above the line. Thus, hydrochloric acid is represented by the formula HCl, that is to say, it is a compound of an atom of hydrogen with an atom of chlorine, or of 1 part by weight of hydrogen with 35.5 parts by weight of chlorine; again, sulphuric acid is represented by the formula H2SO4, which is a statement that it consists of 2 atoms of hydrogen, 1 of sulphur, and 4 of oxygen, and consequently of certain relative weights of these elements. A figure placed on the right of a symbol only affects the symbol to which it is attached, but when figures are placed in front of several symbols all are affected by it, thus 2H2SO4 means H2SO4 taken twice.

The distribution of weight in chemical change is readily expressed in the form of equations by the aid of these symbols; the equation

2HCl + Zn = ZnCl2 + H2,

for example, is to be read as meaning that from 73 parts of hydrochloric acid and 65 parts of zinc, 136 parts of zinc chloride and 2 parts of hydrogen are produced. The + sign is invariably employed in this way either to express combination or action upon, the meaning usually attached to the use of the sign = being that from such and such bodies such and such other bodies are formed. 41

Usually, when the symbols of the elements are written or printed with a figure to the right, it is understood that this indicates a molecule of the element, the symbol alone representing an atom. Thus, the symbols H2 and P4 indicate that the molecules of hydrogen and phosphorus respectively contain 2 and 4 atoms. Since, according to the molecular theory, in all cases of chemical change the action is between molecules, such symbols as these ought always to be employed. Thus, the formation of hydrochloric acid from hydrogen and chlorine is correctly represented by the equation

H2 + Cl2 = 2HCl;

that is to say, a molecule of hydrogen and a molecule of chlorine give rise to two molecules of hydrochloric acid; whilst the following equation merely represents the relative weights of the elements which enter into reaction, and is not a complete expression of what is supposed to take place:—

H + Cl = HCl.

In all cases it is usual to represent substances by formulae which to the best of our knowledge express their molecular composition in the state of gas, and not merely the relative number of atoms which they contain; thus, acetic acid consists of carbon, hydrogen and oxygen in the proportion of one atom of carbon, two of hydrogen, and one of oxygen, but its molecular weight corresponds to the formula C2H4O2, which therefore is always employed to represent acetic acid. When chemical change is expressed with the aid of molecular formulae not only is the distribution of weight represented, but by the mere inspection of the symbols it is possible to deduce from the law of gaseous combination mentioned above, the relative volumes which the agents and resultants occupy in the state of gas if measured at the same temperature and under the same pressure. Thus, the equation

2H2 + O2= 2H2O

not only represents that certain definite weights of hydrogen and oxygen furnish a certain definite weight of the compound which we term water, but that if the water in the state of gas, the hydrogen and the oxygen are all measured at the same temperature and pressure, the volume occupied by the oxygen is only half that occupied by the hydrogen, whilst the resulting water-gas will only occupy the same volume as the hydrogen. In other words, 2 volumes of oxygen and 4 volumes of hydrogen furnish 4 volumes of water-gas. A simple equation like this, therefore, when properly interpreted, affords a large amount of information. One other instance may be given; the equation

2NH3 = N2 + 3H2

represents the decomposition of ammonia gas into nitrogen and hydrogen gases by the electric spark, and it not only conveys the information that a certain relative weight of ammonia, consisting of certain relative weights of hydrogen and nitrogen, is broken up into certain relative weights of hydrogen and nitrogen, but also that the nitrogen will be contained in half the space which contained the ammonia, and that the volume of the hydrogen will be one and a half times as great as that of the original ammonia, so that in the decomposition of ammonia the volume becomes doubled.

Formulae which merely express the relative number of atoms of the different elements present in a compound are termed empirical formulae, and the formulae of all compounds whose molecular weights are undetermined are necessarily empirical. The molecular formula of a compound, however, is always a simple multiple of the empirical formula, if not identical with it; thus, the empirical formula of acetic acid is CH2O, and its molecular formula is C2H4O2, or twice CH2O. In addition to empirical and molecular formulae, chemists are in the habit of employing various kinds of rational formulae, called structural, constitutional or graphic formulae, &c., which not only express the molecular composition of the compounds to which they apply, but also embody certain assumptions as to the manner in which the constituent atoms are arranged, and convey more or less information with regard to the nature of the compound itself, viz. the class to which it belongs, the manner in which it is formed, and the behaviour it will exhibit under various circumstances. Before explaining these formulae it will be necessary, however, to consider the differences in combining power exhibited by the various elements.

Valency.—It is found that the number of atoms of a given element, of chlorine, for example, which unite with an atom of each of the other elements is very variable. Thus, hydrogen unites with but a single atom of chlorine, zinc with two, boron with three, silicon with four, phosphorus with five and tungsten with six. Those elements which are equivalent in combining or displacing power to a single atom of hydrogen are said to be univalent or monad elements; whilst those which are equivalent to two atoms of hydrogen are termed bivalent or dyad elements; and those equivalent to three, four, five or six atoms of hydrogen triad, tetrad, pentad or hexad elements. But not only is the combining power or valency (atomicity) of the elements different, it is also observed that one element may combine with another in several proportions, or that its valency may vary; for example, phosphorus forms two chlorides represented by the formulae PCl3 and PCl5, nitrogen the series of oxides represented by the formulae N2O, NO, (N2O3), N2O4, N2O5, molybdenum forms the chlorides MoCl2, MoCl3, MoCl4, MoCl5, MoCl6(?), and tungsten the chlorides WCl2, WCl4, WCl5, WCl6.

In explanation of these facts it is supposed that each element has a certain number of “units of affinity,” which may be entirely, or only in part, engaged when it enters into combination with other elements; and in those cases in which the entire number of units of affinity are not engaged by other elements, it is supposed that those which are thus disengaged neutralize each other, as it were. For example, in phosphorus pentachloride the five units of affinity possessed by the phosphorus atom are satisfied by the five monad atoms of chlorine, but in the trichloride two are disengaged, and, it may be supposed, satisfy each other. Compounds in which all the units of affinity of the contained elements are engaged are said to be saturated, whilst those in which the affinities of the contained elements are not all engaged by other elements are said to be unsaturated. According to this view, it is necessary to assume that, in all unsaturated compounds, two, or some even number of affinities are disengaged; and also that all elements which combine with an even number of monad atoms cannot combine with an odd number, and vice versa,—in other words, that the number of units of affinity active in the case of any given element must be always either an even or an odd number, and that it cannot be at one time an even and at another an odd number. There are, however, a few remarkable exceptions to this “law.” Thus, it must be supposed that in nitric oxide, NO, an odd number of affinities are disengaged, since a single atom of dyad oxygen is united with a single atom of nitrogen, which in all its compounds with other elements acts either as a triad or pentad. When nitric peroxide, N2O4, is converted into gas, it decomposes, and at about 180° C. its vapour entirely consists of molecules of the composition NO2; while at temperatures between this and 0° C. it consists of a mixture in different proportions of the two kinds of molecules, N2O4 and NO2. The oxide NO2 must be regarded as another instance of a compound in which an odd number of affinities of one of the contained elements are disengaged, since it contains two atoms of dyad oxygen united with a single atom of triad or pentad nitrogen. Again, when tungsten hexachloride is converted into vapour it is decomposed into chlorine and a pentachloride, having a normal vapour density, but as in the majority of its compounds tungsten acts as a hexad, we apparently must regard its pentachloride as a compound in which an odd number of free affinities are disengaged. Hitherto no explanation has been given of these exceptions to what appears to be a law of almost universal application, viz. that the sum of the units of affinity of all the atoms in a compound is an even number.

The number of units of affinity active in the case of any particular element is largely dependent, however, upon the nature of the element or elements with which it is associated. Thus, an atom of iodine only combines with one of hydrogen, 42 but may unite with three of chlorine, which never combines with more than a single atom of hydrogen; an atom of phosphorus unites with only three atoms of hydrogen, but with five of chlorine, or with four of hydrogen and one of iodine; and the chlorides corresponding to the higher oxides of lead, nickel, manganese and arsenic, PbO2, Ni2O3, MnO2 and AS2O5 do not exist as stable compounds, but the lower chlorides, PbCl2, NiCl2, MnCl2 and AsCl3, are very stable.

The valency of an element is usually expressed by dashes or Roman numerals placed on the right of its symbol, thus: H′, O′′, B′′′, CIV, PV, MoVI; but in constructing graphic formulae the symbols of the elements are written with as many lines attached to each symbol as the element which it represents has units of affinity.

The periodic law (see Element) permits a grouping of the elements according to their valency as follows:—Group O.: helium, neon, argon, krypton and xenon appear to be devoid of valency. Group I.: the alkali metals Li, Na, K, Rb, Cs, and also Ag, monovalent; Cu, monovalent and divalent; Au, monovalent and trivalent. Group II.: the alkaline earth metals Ca, Sr, Ba, and also Be (Gl), Mg, Zn, Cd, divalent; Hg, monovalent and divalent. Group III.: B, trivalent; Al, trivalent, but possibly also tetra- or penta-valent; Ga, divalent and trivalent; In, mono-, di- and tri-valent; Tl, monovalent and trivalent. Group IV.: C, Si, Ge, Zr, Th, tetravalent; Ti, tetravalent and hexavalent; Sn, Pb, divalent and tetravalent; Ce, trivalent and tetravalent. Group V.: N, trivalent and pentavalent, but divalent in nitric oxide; P, As, Sb, Bi, trivalent and pentavalent, the last being possibly divalent in BiO and BiCl2. Group VI.: O, usually divalent, but tetravalent and possibly hexavalent in oxonium and other salts; S, Se, Te, di-, tetra- and hexa-valent; Cr, di-, tri- and hexa-valent; Mo, W, di-, tri-, tetra-, penta- and hexa-valent. Group VII.: H(?), monovalent; the halogens F, Cl, Br, I, usually monovalent, but possibly also tri- and pentavalent; Mn, divalent and trivalent, and possibly heptavalent in permanganates. Group VIII.: Fe, Co, divalent and trivalent; Ni, divalent; Os, Ru, hexavalent and octavalent; Pd, Pt, divalent and tetravalent; Ir, tri-, tetra- and hexa-valent. (See also Valency.)

Constitutional Formulae.—Graphic or constitutional formulae are employed to express the manner in which the constituent atoms of compounds are associated together; for example, the trioxide of sulphur is usually regarded as a compound of an atom of hexad sulphur with three atoms of dyad oxygen, and this hypothesis is illustrated by the graphic formula

When this oxide is brought into contact with water it combines with it forming sulphuric acid, H2SO4.

In this compound only two of the oxygen atoms are wholly associated with the sulphur atom, each of the remaining oxygen atoms being united by one of its affinities to the sulphur atoms, and by the remaining affinity to an atom of hydrogen; thus—

The graphic formula of a sulphate is readily deduced by remembering that the hydrogen atoms are partially or entirely replaced. Thus acid sodium sulphate, normal sodium sulphate, and zinc sulphate have the formulae

Again, the reactions of acetic acid, C2H4O2, show that the four atoms of hydrogen which it contains have not all the same function, and also that the two atoms of oxygen have different functions; the graphic formula which we are led to assign to acetic acid, viz.

serves in a measure to express this, three of the atoms of hydrogen being represented as associated with one of the atoms of carbon, whilst the fourth atom is associated with an atom of oxygen which is united by a single affinity to the second atom of carbon, to which, however, the second atom of oxygen is united by both of its affinities. It is not to be supposed that there are any actual bonds of union between the atoms; graphic formulae such as these merely express the hypothesis that certain of the atoms in a compound come directly within the sphere of attraction of certain other atoms, and only indirectly within the sphere of attraction of others,—an hypothesis to which chemists are led by observing that it is often possible to separate a group of elements from a compound, and to displace it by other elements or groups of elements.

Rational formulae of a much simpler description than these graphic formulae are generally employed. For instance, sulphuric acid is usually represented by the formula SO2(OH)2, which indicates that it may be regarded as a compound of the group SO2 with twice the group OH. Each of these OH groups is equivalent in combining or displacing power to a monad element, since it consists of an atom of dyad oxygen associated with a single atom of monad hydrogen, so that in this case the SO2 group is equivalent to an atom of a dyad element. This formula for sulphuric acid, however, merely represents such facts as that it is possible to displace an atom of hydrogen and an atom of oxygen in sulphuric acid by a single atom of chlorine, thus forming the compound SO3HCl; and that by the action of water on the compound SO2Cl2 twice the group OH, or water minus an atom of hydrogen, is introduced in place of the two monad atoms of chlorine—

SO2Cl2 + 2HOH = SO2(OH)2 + 2HCl.
  Water.    Sulphuric acid.

Constitutional formulae like these, in fact, are nothing more than symbolic expressions of the character of the compounds which they represent, the arrangement of symbols in a certain definite manner being understood to convey certain information with regard to the compounds represented.

Groups of two or more atoms like SO2 and OH, which are capable of playing the part of elementary atoms (that is to say, which can be transferred from compound to compound), are termed compound radicals, the elementary atoms being simple radicals. Thus, the atom of hydrogen is a monad simple radical, the atom of oxygen a dyad simple radical, whilst the group OH is a monad compound radical.

It is often convenient to regard compounds as formed upon certain types; alcohol, for example, may be said to be a compound formed upon the water type, that is to say, a compound formed from water by displacing one of the atoms of hydrogen by the group of elements C2H5, thus—

Constitutional formulae become of preponderating importance when we consider the more complicated inorganic and especially organic compounds. Their full significance is treated in the section of this article dealing with organic chemistry, and in the articles Isomerism and Stereo-isomerism.

Chemical Action.—Chemical change or chemical action may be said to take place whenever changes occur which involve an alteration in the composition of molecules, and may be the result of the action of agents such as heat, electricity or light, or of two or more elements or compounds upon each other.

Three kinds of changes are to be distinguished, viz. changes which involve combination, changes which involve decomposition or separation, and changes which involve at the same time both decomposition and combination. Changes of the first and second kind, according to our views of the constitution of molecules, are probably of very rare occurrence; in fact, chemical action appears almost always to involve the occurrence of both these kinds of change, for, as already pointed out, we must assume that the molecules of hydrogen, oxygen and several other elements are diatomic, or that they consist of two atoms. Indeed, it appears probable that with few exceptions the elements 43 are all compounds of similar atoms united together by one or more units of affinity, according to their valencies. If this be the case, however, it is evident that there is no real distinction between the reactions which take place when two elements combine together and when an element in a compound is displaced by another. The combination, as it is ordinarily termed, of chlorine with hydrogen, and the displacement of iodine in potassium iodide by the action of chlorine, may be cited as examples; if these reactions are represented, as such reactions very commonly are, by equations which merely express the relative weights of the bodies which, enter, into reaction, and of the products, thus—

they appear to differ in character; but if they are correctly represented by molecular equations, or equations which express the relative number of molecules which enter into reaction and which result from the reaction, it will be obvious that the character of the reaction is substantially the same in both cases, and that both are instances of the occurrence of what is ordinarily termed double decomposition—

In all cases of chemical change energy in the form of heat is either developed or absorbed, and the amount of heat developed or absorbed in a given reaction is as definite as are the weights of the substance engaged in the reaction. Thus, in the production of hydrochloric acid from hydrogen and chlorine 22,000 calories are developed; in the production of hydrobromic acid from hydrogen and bromine, however, only 8440 calories are developed; and in the formation of hydriodic acid from hydrogen and iodine 6040 calories are absorbed.

This difference in behaviour of the three elements, chlorine, bromine and iodine, which in many respects exhibit considerable resemblance, may be explained in the following manner. We may suppose that in the formation of gaseous hydrochloric acid from gaseous chlorine and hydrogen, according to the equation

H2 + Cl2 = HCl + HCl,

a certain amount of energy is expended in separating the atoms of hydrogen in the hydrogen molecule, and the atoms of chlorine in the chlorine molecule, from each other; but that heat is developed by the combination of the hydrogen atoms with the chlorine atoms, and that, as more energy is developed by the union of the atoms of hydrogen and chlorine than is expended in separating the hydrogen atoms from each other and the chlorine atoms from one another, the result of the action of the two elements upon each other is the development of heat,—the amount finally developed in the reaction being the difference between that absorbed in decomposing the elementary molecules and that developed by the combination of the atoms of chlorine and hydrogen. In the formation of gaseous hydrobromic acid from liquid bromine and gaseous hydrogen—

H2 + Br2 = HBr + HBr,

in addition to the energy expended in decomposing the hydrogen and bromine molecules, energy is also expended in converting the liquid bromine into the gaseous condition, and probably less heat is developed by the combination of bromine and hydrogen than by the combination of chlorine and hydrogen, so that the amount of heat finally, developed is much less than is developed in the formation of hydrochloric acid. Lastly, in the production of gaseous hydriodic acid from hydrogen and solid iodine—

H2 + I2 = HI + HI,

so much energy is expended in the decomposition of the hydrogen and iodine molecules and in the conversion of the iodine into the gaseous condition, that the heat which it may be supposed is developed by the combination of the hydrogen and iodine atoms is insufficient to balance the expenditure, and the final result is therefore negative; hence it is necessary in forming hydriodic acid from its elements to apply heat continuously.

These compounds also afford examples of the fact that, generally speaking, those compounds are most readily formed, and are most stable, in the formation of which the most heat is developed. Thus, chlorine enters into reaction with hydrogen, and removes hydrogen from hydrogenized bodies, far more readily than bromine; and hydrochloric acid is a far more stable substance than hydrobromic acid, hydriodic acid being greatly inferior even to hydrobromic acid in stability. Compounds formed with the evolution of heat are termed exothermic, while those formed with an absorption are termed endothermic. Explosives are the commonest examples of endothermic compounds.

When two substances which by their action upon each other develop much heat enter into reaction, the reaction is usually complete without the employment of an excess of either; for example, when a mixture of hydrogen and oxygen, in the proportions to form water—

2H2 + O2 = 2OH2,

is exploded, it is entirely converted into water. This is also the case if two substances are brought together in solution, by the action of which upon each other a third body is formed which is insoluble in the solvent employed, and which also does not tend to react upon any of the substances present; for instance, when a solution of a chloride is added to a solution of a silver salt, insoluble silver chloride is precipitated, and almost the whole of the silver is removed from solution, even if the amount of the chloride employed be not in excess of that theoretically required.

But if there be no tendency to form an insoluble compound, Or one which is not liable to react upon any of the other substances present, this is no longer the case. For example, when a solution of a ferric salt is added to a solution of potassium thiocyanate, a deep red coloration is produced, owing to the formation of ferric thiocyanate. Theoretically the reaction takes place in the case of ferric nitrate in the manner represented by the equation

but it is found that even when more than sixty times the amount of potassium thiocyanate required by this equation is added, a portion of the ferric nitrate still remains unconverted, doubtless owing to the occurrence of the reverse change—

Fe(CNS)3 + 3KNO3 = Fe(NO3)3 + 3KCNS.

In this, as in most other cases in which substances act upon one another under such circumstances that the resulting compounds are free to react, the extent to which the different kinds of action which may occur take place is dependent upon the mass of the substances present in the mixture. As another instance of this kind, the decomposition of bismuth chloride by water may be cited. If a very large quantity of water be added, the chloride is entirely decomposed in the manner represented by the equation—

the oxychloride being precipitated; but if smaller quantities of water be added the decomposition is incomplete, and it is found that the extent to which decomposition takes place is proportional to the quantity of water employed, the decomposition being incomplete, except in presence of large quantities of water, because of the occurrence of the reverse action—

BiOCl + 2HCl = BiCl3 + OH2.

Chemical change which merely involves simple decomposition is thus seen to be influenced by the masses of the reacting substances and the presence of the products of decomposition; in other words the system of reacting substances and resultants form a mixture in which chemical action has apparently ceased, or the system is in equilibrium. Such reactions are termed reversible (see Chemical Action). 44

III. Inorganic Chemistry

Inorganic chemistry is concerned with the descriptive study of the elements and their compounds, except those of carbon. Reference should be made to the separate articles on the different elements and the more important compounds for their preparation, properties and uses. In this article the development of this branch of the science is treated historically.

The earliest discoveries in inorganic chemistry are to be found in the metallurgy, medicine and chemical arts of the ancients. The Egyptians obtained silver, iron, copper, lead, zinc and tin, either pure or as alloys, by smelting the ores; mercury is mentioned by Theophrastus (c. 300 B.C.). The manufacture of glass, also practised in Egypt, demanded a knowledge of sodium or potassium carbonates; the former occurs as an efflorescence on the shores of certain lakes; the latter was obtained from wood ashes. Many substances were used as pigments: Pliny records white lead, cinnabar, verdigris and red oxide of iron; and the preparation of coloured glasses and enamels testifies to the uses to which these and other substances were put. Salts of ammonium were also known; while alum was used as a mordant in dyeing. Many substances were employed in ancient medicine: galena was the basis of a valuable Egyptian cosmetic and drug; the arsenic sulphides, realgar and orpiment, litharge, alum, saltpetre, iron rust were also used. Among the Arabian and later alchemists we find attempts made to collate compounds by specific properties, and it is to these writers that we are mainly indebted for such terms as “alkali,” “sal,” &c. The mineral acids, hydrochloric, nitric and sulphuric acids, and also aqua regia (a mixture of hydrochloric and nitric acids) were discovered, and the vitriols, alum, saltpetre, sal-ammoniac, ammonium carbonate, silver nitrate (lunar caustic) became better known. The compounds of mercury attracted considerable attention, mainly on account of their medicinal properties; mercuric oxide and corrosive sublimate were known to pseudo-Geber, and the nitrate and basic sulphate to “Basil Valentine.” Antimony and its compounds formed the subject of an elaborate treatise ascribed to this last writer, who also contributed to our knowledge of the compounds of zinc, bismuth and arsenic. All the commonly occurring elements and compounds appear to have received notice by the alchemists; but the writings assigned to the alchemical period are generally so vague and indefinite that it is difficult to determine the true value of the results obtained.

In the succeeding iatrochemical period, the methods of the alchemists were improved and new ones devised. Glauber showed how to prepare hydrochloric acid, spiritus salis, by heating rock-salt with sulphuric acid, the method in common use to-day; and also nitric acid from saltpetre and arsenic trioxide. Libavius obtained sulphuric acid from many substances, e.g. alum, vitriol, sulphur and nitric acid, by distillation. The action of these acids on many metals was also studied; Glauber obtained zinc, stannic, arsenious and cuprous chlorides by dissolving the metals in hydrochloric acid, compounds hitherto obtained by heating the metals with corrosive sublimate, and consequently supposed to contain mercury. The scientific study of salts dates from this period, especial interest being taken in those compounds which possessed a medicinal or technical value. In particular, the salts of potassium, sodium and ammonium were carefully investigated, but sodium and potassium salts were rarely differentiated.9 The metals of the alkaline-earths were somewhat neglected; we find Georg Agricola considering gypsum (calcium sulphate) as a compound of lime, while calcium nitrate and chloride became known at about the beginning of the 17th century. Antimonial, bismuth and arsenical compounds were assiduously studied, a direct consequence of their high medicinal importance; mercurial and silver compounds were investigated for the same reason. The general tendency of this period appears to have taken the form of improving and developing the methods of the alchemists; few new fields were opened, and apart from a more complete knowledge of the nature of salts, no valuable generalizations were attained.

The discovery of phosphorus by Brand, a Hamburg alchemist, in 1669 excited chemists to an unwonted degree; it was also independently prepared by Robert Boyle and J. Kunckel, Brand having kept his process secret. Towards the middle of the 18th century two new elements were isolated: cobalt by G. Brandt in 1742, and nickel by A.F. Cronstedt in 1750. These discoveries were followed by Daniel Rutherford’s isolation of nitrogen in 1772, and by K. Scheele’s isolation of chlorine and oxygen in 1774 (J. Priestley discovered oxygen independently at about the same time), and his investigation of molybdic and tungstic acids in the following year; metallic molybdenum was obtained by P.J. Hjelm in 1783, and tungsten by Don Fausto d’Elhuyar; manganese was isolated by J.G. Gahn in 1774. In 1784 Henry Cavendish thoroughly examined hydrogen, establishing its elementary nature; and he made the far-reaching discovery that water was composed of two volumes of hydrogen to one of oxygen.

The phlogistic theory, which pervaded the chemical doctrine of this period, gave rise to continued study of the products of calcination and combustion; it thus happened that the knowledge of oxides and oxidation products was considerably developed. The synthesis of nitric acid by passing electric sparks through moist air by Cavendish is a famous piece of experimental work, for in the first place it determined the composition of this important substance, and in the second place the minute residue of air which would not combine, although ignored for about a century, was subsequently examined by Lord Rayleigh and Sir William Ramsay, who showed that it consists of a mixture of elementary substances—argon, krypton, neon and xenon (see Argon).

The 18th century witnessed striking developments in pneumatic chemistry, or the chemistry of gases, which had been begun by van Helmont, Mayow, Hales and Boyle. Gases formerly considered to be identical came to be clearly distinguished, and many new ones were discovered. Atmospheric air was carefully investigated by Cavendish, who showed that it consisted of two elementary constituents: nitrogen, which was isolated by Rutherford in 1772, and oxygen, isolated in 1774; and Black established the presence, in minute quantity, of carbon dioxide (van Helmont’s gas sylvestre). Of the many workers in this field, Priestley occupies an important position. A masterly device, initiated by him, was to collect gases over mercury instead of water; this enabled him to obtain gases previously only known in solution, such as ammonia, hydrochloric acid, silicon fluoride and sulphur dioxide. Sulphuretted hydrogen and nitric oxide were discovered at about the same time.

Returning to the history of the discovery of the elements and their more important inorganic compounds, we come in 1789 to M.H. Klaproth’s detection of a previously unknown constituent of the mineral pitchblende. He extracted a substance to which he assigned the character of an element, naming it uranium (from Οὐρανός, heaven); but it was afterwards shown by E.M. Péligot, who prepared the pure metal, that Klaproth’s product was really an oxide. This element was investigated at a later date by Sir Henry Roscoe, and more thoroughly and successfully by C. Zimmermann and Alibegoff. Pitchblende attained considerable notoriety towards the end of the 19th century on account of two important discoveries. The first, made by Sir William Ramsay in 1896, was that the mineral evolved a peculiar gas when treated with sulphuric acid; this gas, helium (q.v.), proved to be identical with a constituent of the sun’s atmosphere, detected as early as 1868 by Sir Norman Lockyer during a spectroscopic examination of the sun’s chromosphere. The second discovery, associated with the Curies, is that of the peculiar properties exhibited by the impure substance, and due to a constituent named radium. The investigation of this substance and its properties (see Radioactivity) has proceeded so far as to render it probable that the theory of the unalterability 45 of elements, and also the hitherto accepted explanations of various celestial phenomena—the source of solar energy and the appearances of the tails of comets—may require recasting.

In the same year as Klaproth detected uranium, he also isolated zirconia or zirconium oxide from the mineral variously known as zircon, hyacinth, jacynth and jargoon; but he failed to obtain the metal, this being first accomplished some years later by Berzelius, who decomposed the double potassium zirconium fluoride with potassium. In the following year, 1795, Klaproth announced the discovery of a third new element, titanium; its isolation (in a very impure form), as in the case of zirconium, was reserved for Berzelius.

Passing over the discovery of carbon disulphide by W.A. Lampadius in 1796, of chromium by L.N. Vauquelin in 1797, and Klaproth’s investigation of tellurium in 1798, the next important series of observations was concerned with platinum and the allied metals. Platinum had been described by Antonio de Ulloa in 1748, and subsequently discussed by H.T. Scheffer in 1752. In 1803 W.H. Wollaston discovered palladium, especially interesting for its striking property of absorbing (“occluding”) as much as 376 volumes of hydrogen at ordinary temperatures, and 643 volumes at 90°. In the following year he discovered rhodium; and at about the same time Smithson Tennant added two more to the list—iridium and osmium; the former was so named from the changing tints of its oxides (ῒρις, rainbow), and the latter from the odour of its oxide (ὀσμή, smell). The most recently discovered “platinum metal,” ruthenium, was recognized by C.E. Claus in 1845. The great number and striking character of the compounds of this group of metals have formed the subject of many investigations, and already there is a most voluminous literature. Berzelius was an early worker in this field; he was succeeded by Bunsen, and Deville and Debray, who worked out the separation of rhodium; and at a later date by P.T. Cleve, the first to make a really thorough study of these elements and their compounds. Of especial note are the curious compounds formed by the union of carbon monoxide with platinous chloride, discovered by Paul Schützenberger and subsequently investigated by F.B. Mylius and F. Foerster and by Pullinger; the phosphoplatinic compounds formed primarily from platinum and phosphorus pentachloride; and also the “ammino” compounds, formed by the union of ammonia with the chloride, &c., of these metals, which have been studied by many chemists, especially S.M. Jörgensen. Considerable uncertainty existed as to the atomic weights of these metals, the values obtained by Berzelius being doubtful. K.F.O. Seubert redetermined this constant for platinum, osmium and iridium; E.H. Keiser for palladium, and A.A. Joly for ruthenium.

The beginning of the 19th century witnessed the discovery of certain powerful methods for the analysis of compounds and the isolation of elements. Berzelius’s investigation of the action of the electric current on salts clearly demonstrated the invaluable assistance that electrolysis could render to the isolator of elements; and the adoption of this method by Sir Humphry Davy for the analysis of the hydrates of the metals of the alkalis and alkaline earths, and the results which he thus achieved, established its potency. In 1808 Davy isolated sodium and potassium; he then turned his attention to the preparation of metallic calcium, barium, strontium and magnesium. Here he met with greater difficulty, and it is to be questioned whether he obtained any of these metals even in an approximately pure form (see Electrometallurgy). The discovery of boron by Gay Lussac and Davy in 1809 led Berzelius to investigate silica (silex). In the following year he announced that silica was the oxide of a hitherto unrecognized element, which he named silicium, considering it to be a metal. This has proved to be erroneous; it is non-metallic in character, and its name was altered to silicon, from analogy with carbon and boron. At the same time Berzelius obtained the element, in an impure condition, by fusing silica with charcoal and iron in a blast furnace; its preparation in a pure condition he first accomplished in 1823, when he invented the method of heating double potassium fluorides with metallic potassium. The success which attended his experiments in the case of silicon led him to apply it to the isolation of other elements. In 1824 he obtained zirconium from potassium zirconium fluoride; the preparation of (impure) titanium quickly followed, and in 1828 he obtained thorium. A similar process, and equally efficacious, was introduced by F. Wöhler in 1827. It consisted in heating metallic chlorides with potassium, and was first applied to aluminium, which was isolated in 1827; in the following year, beryllium chloride was analysed by the same method, beryllium oxide (berylla or glucina) having been known since 1798, when it was detected by L. N. Vauquelin in the gem-stone beryl.

In 1812 B. Courtois isolated the element iodine from “kelp,” the burnt ashes of marine plants. The chemical analogy of this substance to chlorine was quickly perceived, especially after its investigation by Davy and Gay Lussac. Cyanogen, a compound which in combination behaved very similarly to chlorine and iodine, was isolated in 1815 by Gay Lussac. This discovery of the first of the then-styled “compound radicals” exerted great influence on the prevailing views of chemical composition. Hydrochloric acid was carefully investigated at about this time by Davy, Faraday and Gay Lussac, its composition and the elementary nature of chlorine being thereby established.

In 1817 F. Stromeyer detected a new metallic element, cadmium, in certain zinc ores; it was rediscovered at subsequent dates by other observers and its chemical resemblance to zinc noticed. In the same year Berzelius discovered selenium in a deposit from sulphuric acid chambers, his masterly investigation including a study of the hydride, oxides and other compounds. Selenic acid was discovered by E. Mitscherlich, who also observed the similarity of the crystallographic characters of selenates and sulphates, which afforded valuable corroboration of his doctrine of isomorphism. More recent and elaborate investigations in this direction by A.E.H. Tutton have confirmed this view.

In 1818 L.J. Thénard discovered hydrogen dioxide, one of the most interesting inorganic compounds known, which has since been carefully investigated by H.E. Schöne, M. Traube, Wolfenstein and others. About the same time, J.A. Arfvedson, a pupil of Berzelius, detected a new element, which he named lithium, in various minerals—notably petalite. Although unable to isolate the metal, he recognized its analogy to sodium and potassium; this was confirmed by R. Bunsen and A. Matthiessen in 1855, who obtained the metal by electrolysis and thoroughly examined it and its compounds. Its crimson flame-coloration was observed by C.G. Gmelin in 1818.

The discovery of bromine in 1826 by A.J. Balard completed for many years Berzelius’s group of “halogen” elements; the remaining member, fluorine, notwithstanding many attempts, remained unisolated until 1886, when Henri Moissan obtained it by the electrolysis of potassium fluoride dissolved in hydrofluoric acid. Hydrobromic and hydriodic acids were investigated by Gay Lussac and Balard, while hydrofluoric acid received considerable attention at the hands of Gay Lussac, Thénard and Berzelius. We may, in fact, consider that the descriptive study of the various halogen compounds dates from about this time. Balard discovered chlorine monoxide in 1834, investigating its properties and reactions; and his observations on hypochlorous acid and hypochlorites led him to conclude that “bleaching-powder” or “chloride of lime” was a compound or mixture in equimolecular proportions of calcium chloride and hypochlorite, with a little calcium hydrate. Gay Lussac investigated chloric acid; Stadion discovered perchloric acid, since more fully studied by G.S. Serullas and Roscoe; Davy and Stadion investigated chlorine peroxide, formed by treating potassium chlorate with sulphuric acid. Davy also described and partially investigated the gas, named by him “euchlorine,” obtained by heating potassium chlorate with hydrochloric acid; this gas has been more recently examined by Pebal. The oxy-acids of iodine were investigated by Davy and H.G. Magnus; periodic acid, discovered by the latter, is characterized by the striking complexity of its salts as pointed out by Kimmins.

46 In 1830 N.G. Sefström definitely proved the existence of a metallic element vanadium, which had been previously detected (in 1801) in certain lead ores by A.M. del Rio; subsequent elaborate researches by Sir Henry Roscoe showed many inaccuracies in the conclusions of earlier workers (for instance, the substance considered to be the pure element was in reality an oxide) and provided science with an admirable account of this element and its compounds. B.W. Gerland contributed to our knowledge of vanadyl salts and the vanadic acids. Chemically related to vanadium are the two elements tantalum and columbium or niobium. These elements occur in the minerals columbite and tantalite, and their compounds became known in the early part of the 19th century by the labours of C. Hatchett, A.G. Ekeberg, W.H. Wollaston and Berzelius. But the knowledge was very imperfect; neither was it much clarified by H. Rose, who regarded niobium oxide as the element. The subject was revived in 1866 by C.W. Blomstrand and J.C. Marignac, to whom is due the credit of first showing the true chemical relations of these elements. Subsequent researches by Sainte Claire Deville and L.J. Troost, and by A.G. Krüss and L.E. Nilson, and subsequently (1904) by Hall, rendered notable additions to our knowledge of these elements and their compounds. Tantalum has in recent years been turned to economic service, being employed, in the same manner as tungsten, for the production of the filaments employed in incandescent electric lighting.

In 1833 Thomas Graham, following the paths already traced out by E.D. Clarke, Gay Lussac and Stromeyer, published his masterly investigation of the various phosphoric acids and their salts, obtaining results subsequently employed by J. von Liebig in establishing the doctrine of the characterization and basicity of acids. Both phosphoric and phosphorous acids became known, although imperfectly, towards the end of the 18th century; phosphorous acid was first obtained pure by Davy in 1812, while pure phosphorous oxide, the anhydride of phosphorous acid, remained unknown until T.E. Thorpe’s investigation of the products of the slow combustion of phosphorus. Of other phosphorus compounds we may here notice Gengembre’s discovery of phosphuretted hydrogen (phosphine) in 1783, the analogy of which to ammonia was first pointed out by Davy and supported at a later date by H. Rose; liquid phosphuretted hydrogen was first obtained by Thénard in 1838; and hypophosphorous acid was discovered by Dulong in 1816. Of the halogen compounds of phosphorus, the trichloride was discovered by Gay Lussac and Thénard, while the pentachloride was obtained by Davy. The oxychloride, bromides, and other compounds were subsequently discovered; here we need only notice Moissan’s preparation of the trifluoride and Thorpe’s discovery of the pentafluoride, a compound of especial note, for it volatilizes unchanged, giving a vapour of normal density and so demonstrating the stability of a pentavalent phosphorus compound (the pentachloride and pentabromide dissociate into a molecule of the halogen element and phosphorus trichloride).

In 1840 C.F. Schönbein investigated ozone, a gas of peculiar odour (named from the Gr. ὄζειν, to smell) observed in 1785 by Martin van Marum to be formed by the action of a silent electric discharge on the oxygen of the air; he showed it to be an allotropic modification of oxygen, a view subsequently confirmed by Marignac, Andrews and Soret. In 1845 a further contribution to the study of allotropy was made by Anton Schrötter, who investigated the transformations of yellow and red phosphorus, phenomena previously noticed by Berzelius, the inventor Of the term “allotropy.” The preparation of crystalline boron in 1856 by Wöhler and Sainte Claire Deville showed that this element also existed in allotropic forms, amorphous boron having been obtained simultaneously and independently in 1809 by Gay Lussac and Davy. Before leaving this phase of inorganic chemistry, we may mention other historical examples of allotropy. Of great importance is the chemical identity of the diamond, graphite and charcoal, a fact demonstrated in part by Lavoisier in 1773, Smithson Tennant in 1706, and by Sir George Steuart-Mackenzie (1780-1848), who showed that equal weights of these three substances yielded the same weight of carbon dioxide on combustion. The allotropy of selenium was first investigated by Berzelius; and more fully in 1851 by J.W. Hittorf, who carefully investigated the effects produced by heat; crystalline selenium possesses a very striking property, viz. when exposed to the action of light its electric conductivity increases. Another element occurring in allotropic forms is sulphur, of which many forms have been described. E. Mitscherlich was an early worker in this field. A modification known as “black sulphur,” soluble in water, was announced by F.L. Knapp in 1848, and a colloidal modification was described by H. Debus. The dynamical equilibrium between rhombic, liquid and monosymmetric sulphur has been worked out by H.W. Bakhuis Roozeboom. The phenomenon of allotropy is not confined to the non-metals, for evidence has been advanced to show that allotropy is far commoner than hitherto supposed. Thus the researches of Carey Lea, E.A. Schneider and others, have proved the existence of “colloidal silver”; similar forms of the metals gold, copper, and of the platinum metals have been described. The allotropy of arsenic and antimony is also worthy of notice, but in the case of the first element the variation is essentially non-metallic, closely resembling that of phosphorus. The term allotropy has also been applied to inorganic compounds, identical in composition, but assuming different crystallographic forms. Mercuric oxide, sulphide and iodide; arsenic trioxide; titanium dioxide and silicon dioxide may be cited as examples.

The joint discovery in 1859 of the powerful method of spectrum analysis (see Spectroscopy) by G.R. Kirchhoff and R.W. Bunsen, and its application to the detection and the characterization of elements when in a state of incandescence, rapidly led to the discovery of many hitherto unknown elements. Within two years of the invention the authors announced the discovery of two metals, rubidium and caesium, closely allied to sodium, potassium and lithium in properties, in the mineral lepidolite and in the Dürkheim mineral water. In 1861 Sir William Crookes detected thallium (named from the Gr. θάλλος, a green bud, on account of a brilliant green line in its spectrum) in the selenious mud of the sulphuric acid manufacture; the chemical affinities of this element, on the one hand approximating to the metals of the alkalis, and on the other hand to lead, were mainly established by C.A. Lamy. Of other metals first detected by the spectroscope mention is to be made of indium, determined by F. Reich and H.T. Richter in 1863, and of gallium, detected in certain zinc blendes by Lecoq de Boisbaudran in 1875. The spectroscope has played an all-important part in the characterization of the elements, which, in combination with oxygen, constitute the group of substances collectively named the “rare earths.” The substances occur, in very minute quantity, in a large number of sparingly-distributed and comparatively rare minerals—euxenite, samarksite, cerite, yttrotantalite, &c. Scandinavian specimens of these minerals were examined by J. Gadolin, M.H. Klaproth, and especially by Berzelius; these chemists are to be regarded as the pioneers in this branch of descriptive chemistry. Since their day many chemists have entered the lists, new and powerful methods of research have been devised, and several new elements definitely characterized. Our knowledge on many points, however, is very chaotic; great uncertainty and conflict of evidence circulate around many of the “new elements” which have been announced, so much so that P.T. Cleve proposed to divide the “rare earth” metals into two groups, (1) “perfectly characterized”; (2) “not yet thoroughly characterized.” The literature of this subject is very large. The memorial address on J.C.G. de Marignac, a noted worker in this field, delivered by Cleve, a high authority on this subject, before the London Chemical Society (J.C.S. Trans., 1895, p. 468), and various papers in the same journal by Sir William Crookes, Bohuslav Brauner and others should be consulted for details.

In the separation of the constituents of the complex mixture of oxides obtained from the “rare earth” minerals, the methods 47 generally forced upon chemists are those of fractional precipitation or crystallization; the striking resemblances of the compounds of these elements rarely admitting of a complete separation by simple precipitation and filtration. The extraordinary patience requisite to a successful termination of such an analysis can only be adequately realized by actual research; an idea may be obtained from Crookes’s Select Methods in Analysis. Of recent years the introduction of various organic compounds as precipitants or reagents has reduced the labour of the process; and advantage has also been taken of the fairly complex double salts which these metals form with compounds. The purity of the compounds thus obtained is checked by spectroscopic observations. Formerly the spark- and absorption-spectra were the sole methods available; a third method was introduced by Crookes, who submitted the oxides, or preferably the basic sulphates, to the action of a negative electric discharge in vacuo, and investigated the phosphorescence induced spectroscopically. By such a study in the ultra-violet region of a fraction prepared from crude yttria he detected a new element victorium, and subsequently by elaborate fractionation obtained the element itself.

The first earth of this group to be isolated (although in an impure form) was yttria, obtained by Gadolin in 1794 from the mineral gadolinite, which was named after its discoverer and investigator. Klaproth and Vauquelin also investigated this earth, but without detecting that it was a complex mixture—a discovery reserved for C.G. Mosander. The next discovery, made independently and simultaneously in 1803 by Klaproth and by W. Hisinger and Berzelius, was of ceria, the oxide of cerium, in the mineral cerite found at Ridderhytta, Westmannland, Sweden. These crude earths, yttria and ceria, have supplied most if not all of the “rare earth” metals. In 1841 Mosander, having in 1839 discovered a new element lanthanum in the mineral cerite, isolated this element and also a hitherto unrecognized substance, didymia, from crude yttria, and two years later he announced the determination of two fresh constituents of the same earth, naming them erbia and terbia. Lanthanum has retained its elementary character, but recent attempts at separating it from didymia have led to the view that didymium is a mixture of two elements, praseodymium and neodymium (see Didymium). Mosander’s erbia has been shown to contain various other oxides—thulia, holmia, &c.—but this has not yet been perfectly worked out. In 1878 Marignac, having subjected Mosander’s erbia, obtained from gadolinite, to a careful examination, announced the presence of a new element, ytterbium; this discovery was confirmed by Nilson, who in the following year discovered another element, scandium, in Marignac’s ytterbia. Scandium possesses great historical interest, for Cleve showed that it was one of the elements predicted by Mendeléeff about ten years previously from considerations based on his periodic classification of the elements (see Element). Other elements predicted and characterized by Mendeléeff which have been since realized are gallium, discovered in 1875, and germanium, discovered in 1885 by Clemens Winkler.

In 1880 Marignac examined certain earths obtained from the mineral samarskite, which had already in 1878 received attention from Delafontaine and later from Lecoq de Boisbaudran. He established the existence of two new elements, samarium and gadolinium, since investigated more especially by Cleve, to whom most of our knowledge on this subject is due. In addition to the rare elements mentioned above, there are a score or so more whose existence is doubtful. Every year is attended by fresh “discoveries” in this prolific source of elementary substances, but the paucity of materials and the predilections of the investigators militate in some measure against a just valuation being accorded to such researches. After having been somewhat neglected for the greater attractions and wider field presented by organic chemistry, the study of the elements and their inorganic compounds is now rapidly coming into favour; new investigators are continually entering the lists; the beaten paths are being retravcrsed and new ramifications pursued.

IV. Organic Chemistry

While inorganic chemistry was primarily developed through the study of minerals—a connexion still shown by the French appellation chimie minérale—organic chemistry owes its origin to the investigation of substances occurring in the vegetable and animal organisms. The quest of the alchemists for the philosopher’s stone, and the almost general adherence of the iatrochemists to the study of the medicinal characters and preparation of metallic compounds, stultified in some measure the investigation of vegetable and animal products. It is true that by the distillation of many herbs, resins and similar substances, several organic compounds had been prepared, and in a few cases employed as medicines; but the prevailing classification of substances by physical and superficial properties led to the correlation of organic and inorganic compounds, without any attention being paid to their chemical composition. The clarification and spirit of research so clearly emphasized by Robert Boyle in the middle of the 17th century is reflected in the classification of substances expounded by Nicolas Lémery, in 1675, in his Cours de chymie. Taking as a basis the nature of the source of compounds, he framed three classes: “mineral,” comprising the metals, minerals, earths and stones; “vegetable,” comprising plants, resins, gums, juices, &c.; and “animal,” comprising animals, their different parts and excreta. Notwithstanding the inconsistency of his allocation of substances to the different groups (for instance, acetic acid was placed in the vegetable class, while the acetates and the products of their dry distillation, acetone, &c., were placed in the mineral class), this classification came into favour. The phlogistonists endeavoured to introduce chemical notions to support it: Becher, in his Physica subterranea(1669), stated that mineral, vegetable and animal matter contained the same elements, but that more simple combinations prevailed in the mineral kingdom; while Stahl, in his Specimen Becherianum (1702), held the “earthy” principle to predominate in the mineral class, and the “aqueous” and “combustible” in the vegetable and animal classes. It thus happened that in the earlier treatises on phlogistic chemistry organic substances were grouped with all combustibles.

The development of organic chemistry from this time until almost the end of the 18th century was almost entirely confined to such compounds as had practical applications, especially in pharmacy and dyeing. A new and energetic spirit was introduced by Scheele; among other discoveries this gifted experimenter isolated and characterized many organic acids, and proved the general occurrence of glycerin (Ölsüss) in all oils and fats. Bergman worked in the same direction; while Rouelle was attracted to the study of animal chemistry. Theoretical speculations were revived by Lavoisier, who, having explained the nature of combustion and determined methods for analysing compounds, concluded that vegetable substances ordinarily contained carbon, hydrogen and oxygen, while animal substances generally contained, in addition to these elements, nitrogen, and sometimes phosphorus and sulphur. Lavoisier, to whom chemistry was primarily the chemistry of oxygen compounds, having developed the radical theory initiated by Guyton de Morveau, formulated the hypothesis that vegetable and animal substances were oxides of radicals composed of carbon and hydrogen; moreover, since simple radicals (the elements) can form more than one oxide, he attributed the same character to his hydrocarbon radicals: he considered, for instance, sugar to be a neutral oxide and oxalic acid a higher oxide of a certain radical, for, when oxidized by nitric acid, sugar yields oxalic acid. At the same time, however, he adhered to the classification of Lémery; and it was only when identical compounds were obtained from both vegetable and animal sources that this subdivision was discarded, and the classes were assimilated in the division organic chemistry.

At this time there existed a belief, held at a later date by Berzelius, Gmelin and many others, that the formation of organic compounds was conditioned by a so-called vital force; and the difficulty of artificially realizing this action explained the supposed impossibility of synthesizing organic compounds. 48 This dogma was shaken by Wöhler’s synthesis of urea in 1828. But the belief died hard; the synthesis of urea remained isolated for many years; and many explanations were attempted by the vitalists (as, for instance, that urea was halfway between the inorganic and organic kingdoms, or that the carbon, from which it was obtained, retained the essentials of this hypothetical vital force), but only to succumb at a later date to the indubitable fact that the same laws of chemical combination prevail in both the animate and inanimate kingdoms, and that the artificial or laboratory synthesis of any substance, either inorganic or organic, is but a question of time, once its constitution is determined.10

The exact delimitation of inorganic and organic chemistry engrossed many minds for many years; and on this point there existed considerable divergence of opinion for several decades. In addition to the vitalistic doctrine of the origin of organic compounds, views based on purely chemical considerations were advanced. The atomic theory, and its correlatives—the laws of constant and multiple proportions—had been shown to possess absolute validity so far as well-characterized inorganic compounds were concerned; but it was open to question whether organic compounds obeyed the same laws. Berzelius, in 1813 and 1814, by improved methods of analysis, established that the Daltonian laws of combination held in both the inorganic and organic kingdoms; and he adopted the view of Lavoisier that organic compounds were oxides of compound radicals, and therefore necessarily contained at least three elements—carbon, hydrogen and oxygen. This view was accepted in 1817 by Leopold Gmelin, who, in his Handbuch der Chemie, regarded inorganic compounds as being of binary composition (the simplest being oxides both acid and basic, which by combination form salts also of binary form), and organic compounds as ternary, i.e. composed of three elements; furthermore, he concluded that inorganic compounds could be synthesized, whereas organic compounds could not. A consequence of this empirical division was that marsh gas, ethylene and cyanogen were regarded as inorganic, and at a later date many other hydrocarbons of undoubtedly organic nature had to be included in the same division.

The binary conception of compounds held by Berzelius received apparent support from the observations of Gay Lussac, in 1815, on the vapour densities of alcohol and ether, which pointed to the conclusion that these substances consisted of one molecule of water and one and two of ethylene respectively; and from Pierre Jean Robiquet and Jean Jacques Colin, showing, in 1816, that ethyl chloride (hydrochloric ether) could be regarded as a compound of ethylene and hydrochloric acid.11 Compound radicals came to be regarded as the immediate constituents of organic compounds; and, at first, a determination of their empirical composition was supposed to be sufficient to characterize them. To this problem there was added another in about the third decade of the 19th century—namely, to determine the manner in which the atoms composing the radical were combined; this supplementary requisite was due to the discovery of the isomerism of silver fulminate and silver cyanate by Justus von Liebig in 1823, and to M. Faraday’s discovery of butylene, isomeric with ethylene, in 1825.

The classical investigation of Liebig and Friedrich Wohler on the radical of benzoic acid (“Über das Radikal der Benzoë-säure,” Ann. Chem., 1832, 3, p. 249) is to be regarded as a most important contribution to the radical theory, for it was shown that a radical containing the elements carbon, hydrogen and oxygen, which they named benzoyl (the termination yl coming from the Gr. ὔλη, matter), formed the basis of benzaldehyde, benzoic acid, benzoyl chloride, benzoyl bromide and benzoyl sulphide, benzamide and benzoic ether. Berzelius immediately appreciated the importance of this discovery, notwithstanding that he was compelled to reject the theory that oxygen could not play any part in a compound radical—a view which he previously considered as axiomatic; and he suggested the names “proin” or “orthrin” (from the Gr. πρωί and ὀρθρός, at dawn). However, in 1833, Berzelius reverted to his earlier opinion that oxygenated radicals were incompatible with his electrochemical theory; he regarded benzoyl as an oxide of the radical C14H10, which he named “picramyl” (from πικρός, bitter, and ἀμυγδάλη, almond), the peroxide being anhydrous benzoic acid; and he dismissed the views of Gay Lussac and Dumas that ethylene was the radical of ether, alcohol and ethyl chloride, setting up in their place the idea that ether was a suboxide of ethyl, (C2H5)2O, which was analogous to K2O, while alcohol was an oxide of a radical C2H6; thus annihilating any relation between these two compounds. This view was modified by Liebig, who regarded ether as ethyl oxide, and alcohol as the hydrate of ethyl oxide; here, however, he was in error, for he attributed to alcohol a molecular weight double its true value. Notwithstanding these errors, the value of the “ethyl theory” was perceived; other radicals—formyl, methyl, amyl, acetyl, &c.—were characterized; Dumas, in 1837, admitted the failure of the etherin theory; and, in company with Liebig, he defined organic chemistry as the “chemistry of compound radicals.” The knowledge of compound radicals received further increment at the hands of Robert W. Bunsen, the discoverer of the cacodyl compounds.

The radical theory, essentially dualistic in nature in view of its similarity to the electrochemical theory of Berzelius, was destined to succumb to a unitary theory. Instances had already been recorded of cases where a halogen element replaced hydrogen with the production of a closely allied substance: Gay Lussac had prepared cyanogen chloride from hydrocyanic acid; Faraday, hexachlorethane from ethylene dichloride, &c. Here the electro-negative halogens exercised a function similar to electro-positive hydrogen. Dumas gave especial attention to such substitutions, named metalepsy μετάληψις, exchange); and framed the following empirical laws to explain the reactions:—(1) a body containing hydrogen when substituted by a halogen loses one atom of hydrogen for every atom of halogen introduced; (2) the same holds if oxygen be present, except that when the oxygen is present as water the latter first loses its hydrogen without replacement, and then substitution according to (1) ensues. Dumas went no further that thus epitomizing his observations; and the next development was made in 1836 by Auguste Laurent, who, having amplified and discussed the applicability of Dumas’ views, promulgated his Nucleus Theory, which assumed the existence of “original nuclei or radicals” (radicaux or noyaux fondamentaux) composed of carbon and hydrogen, and “derived nuclei” (radicaux or noyaux dérivés) formed from the original nuclei by the substitution of hydrogen or the addition of other elements, and having properties closely related to the primary nuclei.

Vigorous opposition was made by Liebig and Berzelius, the latter directing his attack against Dumas, whom he erroneously believed to be the author of what was, in his opinion, a pernicious theory. Dumas repudiated the accusation, affirming that he held exactly contrary views to Laurent; but only to admit their correctness in 1839, when, from his own researches and those of Laurent, Malaguti and Regnault, he formulated his type theory. According to this theory a “chemical type” embraced compounds containing the same number of equivalents combined in a like manner and exhibiting similar properties; thus acetic and trichloracetic acids, aldehyde and chloral, marsh gas and chloroform are pairs of compounds referable to the same type. He also postulated, with Regnault, the existence of “molecular or mechanical types” containing substances which, although having the same number of equivalents, are essentially different in characters. His unitary conceptions may be summarized: every chemical compound forms a complete whole, and cannot therefore consist of two parts; and its chemical character depends primarily upon the arrangement and number of the atoms, and, in a lesser degree, upon their chemical nature. 49 More emphatic opposition to the dualistic theory of Berzelius was hardly possible; this illustrious chemist perceived that the validity of his electrochemical theory was called in question, and therefore he waged vigorous war upon Dumas and his followers. But he fought in a futile cause; to explain the facts put forward by Dumas he had to invent intricate and involved hypotheses, which, it must be said, did not meet with general acceptance; Liebig seceded from him, and invited Wöhler to endeavour to correct him. Still, till the last Berzelius remained faithful to his original theory; experiment, which he had hitherto held to be the only sure method of research, he discarded, and in its place he substituted pure speculation, which greatly injured the radical theory. At the same time, however, the conception of radicals could not be entirely displaced, for the researches of Liebig and Wohler, and those made subsequently by Bunsen, demonstrated beyond all doubt the advantages which would accrue from their correct recognition.

A step forward—the fusion of Dumas’, type theory and the radical theory—was made by Laurent and Charles Gerhardt. As early as 1842, Gerhardt in his Précis de chimie organique exhibited a marked leaning towards Dumas’ theory, and it is without doubt that both Dumas and Laurent exercised considerable influence on his views. Unwilling to discard the strictly unitary views of these chemists, or to adopt the copulae theory of Berzelius, he revived the notion of radicals in a new form. According to Gerhardt, the process of substitution consisted of the union of two residues to form a unitary whole; these residues, previously termed “compound radicals,” are atomic complexes which remain over from the interaction of two compounds. Thus, he interpreted the interaction of benzene and nitric acid as C6H6 + HNO3 = C6H5NO2 + H2O, the “residues” of benzene being C6H5 and H, and of nitric acid HO and NO2. Similarly he represented the reactions investigated by Liebig and Wöhler on benzoyl compounds as double decompositions.

This rejuvenation of the notion of radicals rapidly gained favour; and the complete fusion of the radical theory with the theory of types was not long delayed. In 1849 C.A. Wurtz discovered the amines or substituted ammonias, previously predicted by Liebig; A.W. von Hofmann continued the investigation, and established their recognition as ammonia in which one or more hydrogen atoms had been replaced by hydrocarbon radicals, thus formulating the “ammonia type.” In 1850 A.W. Williamson showed how alcohol and ether were to be regarded as derived from water by substituting one or both hydrogen atoms by the ethyl group; he derived acids and the acid anhydrides from the same type; and from a comparison of many inorganic and the simple organic compounds he concluded that this notion of a “water-type” clarified, in no small measure, the conception of the structure of compounds.

These conclusions were co-ordinated in Gerhardt’s “new theory of types.” Taking as types hydrogen, hydrochloric acid, water and ammonia, he postulated that all organic compounds were referable to these four forms: the hydrogen type included hydrocarbons, aldehydes and ketones; the hydrochloric acid type, the chlorides, bromides and iodides; the water type, the alcohols, ethers, monobasic acids, acid anhydrides, and the analogous sulphur compounds; and the ammonia type, the amines, acid-amides, and the analogous phosphorus and arsenic compounds. The recognition of the polybasicity of acids, which followed from the researches of Thomas Graham and Liebig, had caused Williamson to suggest that dibasic acids could be referred to a double water type, the acid radical replacing an atom of hydrogen in each water molecule; while his discovery of tribasic formic ether, CH(OC2H5)3, in 1854 suggested a triple water type. These views were extended by William Odling, and adopted by Gerhardt, but with modifications of Williamson’s aspects. A further generalization was effected by August Kekulé, who rejected the hydrochloric acid type as unnecessary, and introduced the methane type and condensed mixed types. Pointing out that condensed types can only be fused with a radical replacing more than one atom of hydrogen, he laid the foundation of the doctrine of valency, a doctrine of incalculable service to the knowledge of the structure of chemical compounds.

At about the same time Hermann Kolbe attempted a rehabilitation, with certain modifications, of the dualistic conception of Berzelius. He rejected the Berzelian tenet as to the unalterability of radicals, and admitted that they exercised a considerable influence upon the compounds with which they were copulated. By his own investigations and those of Sir Edward Frankland it was proved that the radical methyl existed in acetic acid; and by the electrolysis of sodium acetate, Kolbe concluded that he had isolated this radical; in this, however, he was wrong, for he really obtained ethane, C2H6, and not methyl, CH3. From similar investigations of valerianic acid he was led to conclude that fatty acids were oxygen compounds of the radicals hydrogen, methyl, ethyl, &c., combined with the double carbon equivalent C2. Thus the radical of acetic acid, acetyl,12 was C2H3·C2. (It will be noticed that Kolbe used the atomic weights H=1, C=6, O=8, S=16, &c.; his formulae, however, were molecular formulae, i.e. the molecular weights were the same as in use to-day.) This connecting link, C2, was regarded as essential, while the methyl, ethyl, &c. was but a sort of appendage; but Kolbe could not clearly conceive the manner of copulation.

The brilliant researches of Frankland on the organo-metallic compounds, and his consequent doctrine of saturation capacity or valency of elements and radicals, relieved Kolbe’s views of all obscurity. The doctrine of copulae was discarded, and in 1859 emphasis was given to the view that all organic compounds were derivatives of inorganic by simple substitution processes. He was thus enabled to predict compounds then unknown, e.g. the secondary and tertiary alcohols; and with inestimable perspicacity he proved intimate relations between compounds previously held to be quite distinct. Lactic acid and alanine were shown to be oxy- and amino-propionic acids respectively; glycollic acid and glycocoll, oxy- and amino-acetic acids; salicylic and benzamic acids, oxy- and amino-benzoic acids.

Another consequence of the doctrine of valency was that it permitted the graphic representation of the molecule. The “structure theory” (or the mode of linking of the atoms) of carbon compounds, founded by Butlerow, Kekulé and Couper and, at a later date, marvellously enhanced by the doctrine of stereo-isomerism, due to J.H. van’t Hoff and Le Bel, occupies such a position in organic chemistry that its value can never be transcended. By its aid the molecule is represented as a collection of atoms connected together by valencies in such a manner that the part played by each atom is represented; isomerism, or the existence of two or more chemically different substances having identical molecular weights, is adequately shown; and, most important of all, once the structure is determined, the synthesis of the compound is but a matter of time.

In this summary the leading factors which have contributed to a correct appreciation of organic compounds have so far been considered historically, but instead of continuing this method it has been thought advisable to present an epitome of present-day conclusions, not chronologically, but as exhibiting the principles and subject-matter of our science.

Classification of Organic Compounds.

An apt definition of organic chemistry is that it is “the study of the hydrocarbons and their derivatives.” This description, although not absolutely comprehensive, serves as a convenient starting-point for a preliminary classification, since a great number of substances, including the most important, are directly referable to hydrocarbons, being formed by replacing one or more hydrogen atoms by other atoms or groups. Two distinct types of hydrocarbons exist: (1) those consisting of an open chain of carbon atoms—named the “aliphatic series” (ἄλειφαρ, oil or fat), and (2) those consisting of a closed chain—the “carbocyclic series.” The second series can be further divided 50 into two groups: (1) those exhibiting properties closely analogous to the aliphatic series—the polymethylenes (q.v.), and (2) a series exhibiting properties differing in many respects from the aliphatic and polymethylene compounds, and characterized by a peculiar stability which is to be associated with the disposition of certain carbon valencies not saturated by hydrogen—the “aromatic series.” There also exists an extensive class of compounds termed the “heterocyclic series”—these compounds are derived from ring systems containing atoms other than carbon; this class is more generally allied to the aromatic series than to the aliphatic.

We now proceed to discuss the types of aliphatic compounds; then, the characteristic groupings having been established, an epitome of their derivatives will be given. Carbocyclic rings will next be treated, benzene and its allies in some detail; and finally the heterocyclic nuclei.

Accepting the doctrine of the tetravalency of carbon (its divalency in such compounds as carbon monoxide, various isocyanides, fulminic acid, &c., and its possible trivalency in M. Gomberg’s triphenyl-methyl play no part in what follows), it is readily seen that the simplest hydrocarbon has the formula CH4 named methane, in which the hydrogen atoms are of equal value, and which may be pictured as placed at the vertices of a tetrahedron, the carbon atom occupying the centre. This tetrahedral configuration is based on the existence of only one methylene dichloride, two being necessary if the carbon valencies were directed from the centre of a plane square to its corners, and on the existence of two optical isomers of the formula C.A.B.D.E., C being a carbon atom and A.B.D.E. being different monovalent atoms or radicals (see Stereo-Isomerism). The equivalence of the four hydrogen atoms of methane rested on indirect evidence, e.g. the existence of only one acetic acid, methyl chloride, and other monosubstitution derivatives—until the experimental proof by L. Henry (Zeit. f. Phys. Chem., 1888, 2, p. 553), who prepared the four nitromethanes, CH3NO2, each atom in methane being successively replaced by the nitro-group.

Let us now consider hydrocarbons containing 2 atoms of carbon. Three such compounds are possible according to the number of valencies acting directly between the carbon atoms. Thus, if they are connected by one valency, and the remaining valencies saturated by hydrogen, we obtain the compound H3C·CH3, ethane. This compound may be considered as derived from methane, CH4, by replacing a hydrogen atom by the monovalent group CH3, known as methyl; hence ethane may be named “methylmethane.” If the carbon atoms are connected by two valencies, we obtain a compound H2C:CH2, ethylene; if by three valencies, HC∶CH, acetylene. These last two compounds are termed unsaturated, whereas ethane is saturated. It is obvious that we have derived three combinations of carbon with hydrogen, characterized by containing a single, double, and triple linkage; and from each of these, by the substitution of a methyl group for a hydrogen atom, compounds of the same nature result. Thus ethane gives H3C·CH2·CH3, propane; ethylene gives H2C:CH·CH3, propylene; and acetylene gives HC∶C·CH3, allylene. By continuing the introduction of methyl groups we obtain three series of homologous hydro-carbons given, by the general formulae CnH2n+2, CnH2n, and CnH2n-2, each member differing from the preceding one of the same series by CH2. It will be noticed that compounds containing two double linkages will have the same general formula as the acetylene series; such compounds are known as the “diolefines.” Hydrocarbons containing any number of double or triple linkages, as well as both double and triple linkages, are possible, and a considerable number of such compounds have been prepared.

In methane and ethane the hydrogen atoms are of equal value, and no matter which one may be substituted by another element or group the same compound will result. In propane, on the other hand, the hydrogen atoms attached to the terminal carbon atoms differ from those joined to the medial atom; we may therefore expect to obtain different compounds according to the position of the hydrogen atom substituted. By introducing a methyl group we may obtain CH3·CH2·CH2·CH3, known as “normal” or n-butane, substitution occurring at a terminal atom, or CH3·CH(CH3)·CH3, isobutane, substitution occurring at the medial atom. From n-butane we may derive, by a similar substitution of methyl groups, the two hydrocarbons: (1) CH3·CH2·CH2·CH2·CH3, and (2) CH3·CH(CH3)·CH2·CH3; from isobutane we may also derive two compounds, one identical with (2.), and a new one (3) CH3(CH3)C(CH3)CH3. These three hydrocarbons are isomeric, i.e. they possess the same formula, but differ in constitution. We notice that they may be differentiated as follows: (1) is built up solely of methyl and ·CH2· (methylene) groups and the molecule consists of a single chain; such hydrocarbons are referred to as being normal; (2) has a branch and contains the group ÷CH (methine) in which the free valencies are attached to carbon atoms; such hydrocarbons are termed secondary or iso-; (3) is characterized by a carbon atom linked directly to four other carbon atoms; such hydrocarbons are known as tertiary.

Deferring the detailed discussion of cyclic or ringed hydrocarbons, a correlation of the various types or classes of compounds which may be derived from hydrocarbon nuclei will now be given. It will be seen that each type depends upon a specific radical or atom, and the copulation of this character with any hydrocarbon radical (open or cyclic) gives origin to a compound of the same class.

It is convenient first to consider the effect of introducing one, two, or three hydroxyl (OH) groups into the -CH3, >CH2, and ->CH groups, which we have seen to characterize the different types of hydrocarbons. It may be noticed here that cyclic nuclei can only contain the groups >CH2 and ->CH, the first characterizing the polymethylene and reduced heterocyclic compounds, the second true aromatic compounds.

We proceed to consider various simple derivatives of the alcohols, which we may here regard as hydroxy hydrocarbons, R·OH, where R is an alkyl radical, either aliphatic or cyclic in nature.

The carboxyl group constitutes another convenient starting-point for the orientation of many types of organic compounds. This group may be considered as resulting from the fusion of a carbonyl (:CO) and a hydroxyl (HO·) group; and we may expect to meet with compounds bearing structural resemblances to the derivatives of alcohols and aldehydes (or ketones).

By transformations of the carbonyl group, and at the same time of the hydroxyl group, many interesting types of nitrogen compounds may be correlated.

Cyclic Hydrocarbons and Nuclei.

Having passed in rapid review the various types of compounds derived by substituting for hydrogen various atoms or groups of atoms in hydrocarbons (the separate articles on specific compounds should be consulted for more detailed accounts), we now proceed to consider the closed chain compounds. Here we meet with a great diversity of types: oxygen, nitrogen, sulphur and other elements may, in addition to carbon, combine together in a great number of arrangements to form cyclic nuclei, which exhibit characters closely resembling open-chain compounds in so far as they yield substitution derivatives, and behave as compound radicals. In classifying closed chain compounds, the first step consists in dividing them into: (1) carbocyclic, in which the ring is composed solely of carbon atoms—these are also known as homocyclic or isocyclic on account of the identity of the members of the ring—and (2) heterocyclic, in which different elements go to make up the ring. Two primary divisions of carbocyclic compounds may be conveniently made: (1) those in which the carbon atoms are completely saturated—these are known by the generic term polymethylenes, their general formula being (CH2)n: it will be noticed that they are isomeric with ethylene and its homologues; they differ, however, from this series in not containing a double linkage, but have a ringed structure; and (2) those containing fewer hydrogen atoms than suffice to saturate the carbon valencies—these are known as the aromatic compounds proper, or as benzene compounds, from the predominant part which benzene plays in their constitution.

It was long supposed that the simplest ring obtainable contained six atoms of carbon, and the discovery of trimethylene in 1882 by August Freund by the action of sodium on trimethylene bromide, Br(CH2)3Br, came somewhat as a surprise, especially in view of its behaviour with bromine and hydrogen bromide. In comparison with the isomeric propylene, CH3·HC:CH2, it is remarkably inert, being only very slowly attacked by bromine, which readily combines with propylene. But on the other hand, it is readily converted by hydrobromic acid into normal propyl bromide, CH3·CH2·CH2Br. The separation of carbon atoms united by single affinities in this manner at the time the observation was made was altogether without precedent. A similar behaviour has since been noticed in other trimethylene derivatives, but the fact that bromine, which usually acts so much more readily than hydrobromic acid on unsaturated compounds, should be so inert when hydrobromic acid acts readily is one still needing a satisfactory explanation. A great impetus was given to the study of polymethylene derivatives by the important and unexpected observation made by W.H. Perkin, junr., in 1883, that ethylene and trimethylene bromides are capable of acting in such a way on sodium acetoacetic ester as to form tri- and tetra-methylene rings. Perkin has himself contributed largely to our knowledge of such compounds; penta- and hexa-methylene derivatives have also received considerable attention (see Polymethylenes).

A. von Baeyer has sought to explain the variations in stability manifest in the various polymethylene rings by a purely mechanical hypothesis, the “strain” or Spannungs theory (Ber., 1885, p. 2277). Assuming the four valencies of the carbon atom to be directed from the centre of a regular tetrahedron towards its four corners, the angle at which they meet is 109° 28′. Baeyer supposes that in the formation of carbon ~52 “rings” the valencies become deflected from their positions, and that the tension thus introduced may be deduced from a comparison of this angle with the angles at which the strained valencies would meet. He regards the amount of deflection as a measure of the stability of the “ring.” The readiness with which ethylene is acted on in comparison with other types of hydrocarbon, for example, is in harmony, he considers, with the circumstance that the greatest distortion must be involved in its formation, as if deflected into parallelism each valency will be drawn out of its position through ½.109° 28′. The values in other cases are calculable from the formula ½(1O9° 28′ - a), where a is the internal angle of the regular polygon contained by sides equal in number to the number of the carbon atoms composing the ring. These values are:—

The general behaviour of the several types of hydrocarbons is certainly in accordance with this conception, and it is a remarkable fact that when benzene is reduced with hydriodic acid, it is converted into a mixture of hexamethylene and methylpentamethylene (cf. W. Markownikov, Ann., 1898, 302, p. 1); and many other cases of the conversion of six-carbon rings into five-carbon rings have been recorded (see below, Decompositions of the Benzene Ring). Similar considerations will apply to rings containing other elements besides carbon. As an illustration it may be pointed out that in the case of the two known types of lactones—the γ-lactones, which contain four carbon atoms and one oxygen atom in the ring, are more readily formed and more stable (less readily hydrolysed) than the δ-lactones, which contain one oxygen and five carbon atoms in the ring. That the number of atoms which can be associated in a ring by single affinities is limited there can be no doubt, but there is not yet sufficient evidence to show where the limit must be placed. Baeyer has suggested that his hypothesis may also be applied to explain the instability of acetylene and its derivatives, and the still greater instability of the polyacetylene compounds.

Benzene.

The ringed structure of benzene, C6H6, was first suggested in 1865 by August Kekulé, who represented the molecule by six CH groups placed at the six angles of a regular hexagon, the sides of which denoted the valencies saturated by adjacent carbon atoms, the fourth valencies of each carbon atom being represented as saturated along alternate sides. This formula, notwithstanding many attempts at both disproving and modifying it, has well stood the test of time; the subject has been the basis of constant discussion, many variations have been proposed, but the original conception of Kekulé remains quite as convenient as any of the newer forms, especially when considering the syntheses and decompositions of the benzene complex. It will be seen, however, that the absolute disposition of the fourth valency may be ignored in a great many cases, and consequently the complex may be adequately represented as a hexagon. This symbol is in general use; it is assumed that at each corner there is a CH group which, however, is not always written in; if a hydrogen atom be substituted by another group, then this group is attached to the corner previously occupied by the displaced hydrogen. The following diagrams illustrate these statements:—

We now proceed to consider the properties, syntheses, decompositions and constitution of the benzene complex. It has already been stated that benzene derivatives may be Distinctions between aliphatic and aromatic compounds. regarded as formed by the replacement of hydrogen atoms by other elements or radicals in exactly the same manner as in the aliphatic series. Important differences, however, are immediately met with when we consider the methods by which derivatives are obtained. For example: nitric acid and sulphuric acid readily react with benzene and its homologues with the production of nitro derivatives and sulphonic acids, while in the aliphatic series these acids exert no substituting action (in the case of the olefines, the latter acid forms an addition product); another distinction is that the benzene complex is more stable towards oxidizing agents. This and other facts connected with the stability of benzenoid compounds are clearly shown when we consider mixed aliphatic-aromatic hydrocarbons, i.e. compounds derived by substituting aliphatic radicals in the benzene nucleus; such a compound is methylbenzene or toluene, C6H5·CH3. This compound is readily oxidized to benzoic acid, C6H5·COOH, the aromatic residue being unattacked; nitric and sulphuric acids produce nitro-toluenes, C6H4·CH3·NO2, and toluene sulphonic acids, C6H4·CH3·SO3H; chlorination may result in the formation of derivatives substituted either in the aromatic nucleus or in the side chain; the former substitution occurs most readily, chlor-toluenes, C6H4·CH3·Cl, being formed, while the latter, which needs an elevation in temperature or other auxiliary, yields benzyl chloride, C6H5·CH2Cl, and benzal chloride, C6H5·CHCl2. In general, the aliphatic residues in such mixed compounds retain the characters of their class, while the aromatic residues retain the properties of benzene.

Further differences become apparent when various typical compounds are compared. The introduction of hydroxyl groups into the benzene nucleus gives rise to compounds generically named phenols, which, although resembling the aliphatic alcohols in their origin, differ from these substances in their increased chemical activity and acid nature. The phenols more closely resemble the tertiary alcohols, since the hydroxyl group is linked to a carbon atom which is united to other carbon atoms by its remaining three valencies; hence on oxidation they cannot yield the corresponding aldehydes, ketones or acids (see below, Decompositions of the Benzene Ring). The amines also exhibit striking differences: in the aliphatic series these compounds may be directly formed from the alkyl haloids and ammonia, but in the benzene series this reaction is quite impossible unless the haloid atom be weakened by the presence of other substituents, e.g. nitro groups. Moreover, while methylamine, dimethylamine, and trimethylamine increase in basicity corresponding to the introduction of successive methyl groups, phenylamine or aniline, diphenylamine, and triphenylamine are in decreasing order of basicity, the salts of diphenylamine being decomposed by water. Mixed aromatic-aliphatic amines, both secondary and tertiary, are also more strongly basic than the pure aromatic amines, and less basic than the true aliphatic compounds; e.g. aniline, C6H5·NH2, monomethyl aniline, C6H5·NH·CH3, and dimethyl aniline, C6H5·N(CH3)2, are in increasing order of basicity. These observations may be summarized by saying that the benzene nucleus is more negative in character than the aliphatic residues.

Isomerism of Benzene Derivatives.—Although Kekulé founded his famous benzene formula in 1865 on the assumptions that the six hydrogen atoms in benzene are equivalent and that the molecule is symmetrical, i.e. that two pairs of hydrogen atoms are symmetrically situated with reference to any specified hydrogen atom, the absolute demonstration of the validity of 53 these assumptions was first given by A. Ladenburg in 1874 (see Ber., 1874, 7, p. 1684; 1875, 8, p. 1666; Theorie der aromatischen Verbindungen, 1876). These results may be graphically represented as follows: numbering the hydrogen atoms in cyclical order from 1 to 6, then the first thesis demands that whichever atom is substituted the same compound results, while the second thesis points out that the pairs 2 and 6, and 3 and 5 are symmetrical with respect to 1, or in other words, the di-substitution derivatives 1.2 and 1.6, and also 1.3 and 1.5 are identical. Therefore three di-derivatives are possible, viz. 1.2 or 1.6, named ortho- (o), 1.3 or 1.5, named meta- (m), and 1.4, named para- compounds (p). In the same way it may be shown that three tri-substitution, three tetra-substitution, one penta-substitution, and one hexa-substitution derivative are possible. Of the tri-substitution derivatives, 1.2.3.-compounds are known as “adjacent” or “vicinal” (v), the 1.2.4 as “asymmetrical” (as), the 1.3.5 as “symmetrical” (s); of the tetra-substitution derivatives, 1.2.3.4-compounds are known as “adjacent,” 1.2.3.5 as “asymmetrical,” and 1.2.4.5 as “symmetrical.”

Here we have assumed the substituent groups to be alike; when they are unlike, a greater number of isomers is possible. Thus in the tri-substitution derivatives six isomers, and no more, are possible when two of the substituents are alike; for instance, six diaminobenzoic acids, C6H3(NH2)2COOH, are known; when all are unlike ten isomers are possible; thus, ten oxytoluic acids, C6H3·CH3·OH·COOH, are known. In the case of tetra-substituted compounds, thirty isomers are possible when all the groups are different.

Orientation of Substituent Groups.—The determination of the relative positions of the substituents in a benzene derivative constitutes an important factor in the general investigation of such compounds. Confining our attention, for the present, to di-substitution products we see that there are three distinct series of compounds to be considered. Generally if any group be replaced by another group, then the second group enters the nucleus in the position occupied by the displaced group; this means that if we can definitely orientate three di-derivatives of benzene, then any other compound, which can be obtained from or converted into one of our typical derivatives, may be definitely orientated. Intermolecular transformations—migrations of substituent groups from one carbon atom to another—are of fairly common occurrence among oxy compounds at elevated temperatures. Thus potassium ortho-oxybenzoate is converted into the salt of para-oxybenzoic acid at 220°; the three bromphenols, and also the brombenzenesulphonic acids, yield m-dioxybenzene or resorcin when fused with potash. It is necessary, therefore, to avoid reactions involving such intermolecular migrations when determining the orientation of aromatic compounds.

Substitution of the Benzene Ring.—As a general rule, homologues and mono-derivatives of benzene react more readily with substituting agents than the parent hydrocarbon; for example, phenol is converted into tribromphenol by the action of bromine water, and into the nitrophenols by dilute nitric acid; similar activity characterizes aniline. Not only does the substituent group modify the readiness with which the derivative is attacked, but also the nature of the product. Starting with a mono-derivative, we have seen that a substituent group may enter in either of three positions to form an ortho-, meta-, or para-compound. Experience has shown that such mono-derivatives as nitro compounds, sulphonic acids, carboxylic acids, aldehydes, and ketones yield as a general rule chiefly the meta-compounds, and this is independent of the nature of the second group introduced; on the other hand, benzene haloids, amino-, homologous-, and hydroxy-benzenes yield principally a mixture of the ortho- and para-compounds. These facts are embodied in the “Rule of Crum Brown and J. Gibson” (Jour. Chem. Soc. 61, p. 367): If the hydrogen compound of the substituent already in the benzene nucleus can be directly oxidized to the corresponding hydroxyl compound, then meta-derivatives predominate on further substitution, if not, then ortho- and para-derivatives. By further substitution of ortho- and para-di-derivatives, in general the same tri-derivative [1.2.4] is formed (Ann., 1878, 192, p. 219); meta-compounds yield [1.3.4] and [1.2.3] tri-derivatives, except in such cases as when both substituent groups are strongly acid, e.g. m-dinitrobenzene, then [1.3.5]-derivatives are obtained.

Syntheses of the Benzene Ring.—The characteristic distinctions 54 which exist between aliphatic and benzenoid compounds make the transformations of one class into the other especially interesting.

Decompositions of the Benzene Ring.—We have previously alluded to the relative stability of the benzene complex; consequently reactions which lead to its disruption are all the more interesting, and have engaged the attention of many chemists. If we accept Kekulé’s formula for the benzene nucleus, then we may expect the double linkages to be opened up partially, either by oxidation or reduction, with the formation of di-, tetra-, or hexa-hydro derivatives, or entirely, with the production of open chain compounds. Generally rupture occurs at more than one point; and rarely are the six carbon atoms of the complex regained as an open chain. Certain compounds withstand ring decomposition much more strongly than others; for instance, benzene and its homologues, carboxylic acids, and nitro compounds are much more stable towards oxidizing agents than amino- and oxy-benzenes, aminophenols, quinones, and oxy-carboxylic acids.

Configuration of the Benzene Complex.—The development of the “structure theory” in about 1860 brought in its train an appreciation of the chemical structure of the derivatives of benzene. The pioneer in this field was August Kekulé, who, in 1865 (Ann., 137, p. 129; see also his Lehrbuch der organischen Chemie), submitted his well-known formula for benzene, so founding the “benzene theory” and opening up a problem which, notwithstanding the immense amount of labour since bestowed upon it, still remains imperfectly solved. Arguing from the existence of only one mono-substitution derivative, and of three di-derivatives (statements of which the rigorous proof was then wanting), he was led to arrange the six carbon atoms in a ring, attaching a hydrogen atom to each carbon atom; being left with the fourth carbon valencies, he mutually saturated these in pairs, thus obtaining the symbol I (see below). The value of this ringed structure was readily perceived, but objections were raised with respect to Kekulé’s disposal of the fourth valencies. In 1866 Sir James Dewar proposed an unsymmetrical form (II); while in 1867, A. Claus (Theoretische Betrachtungen und deren Anwendung zur Systematik der organischen Chemie) proposed his diagonal formula (III), and two years later, A. Ladenburg (Ber., 2, p. 140) devised his prism formula (IV), the six carbon atoms being placed at the six corners of a right equilateral triangular prism, with its plane projections (V, VI).

The stronger argument against the ethylenoid linkages demanded by Kekulé’s formula is provided by the remarkable stability towards oxidizing and reducing agents which characterizes all benzenoid compounds. From the fact that reduction products containing either one or two double linkages behave exactly as unsaturated aliphatic compounds, being readily reduced or oxidized, and combining with the halogen elements and haloid acids, it seems probable that in benzenoid compounds the fourth valencies are symmetrically distributed in such a manner as to induce a peculiar stability in the molecule. Such a configuration was proposed in 1887 by H.E. Armstrong (J.C.S. Trans., 1887, p. 258), and shortly afterwards by Baeyer (Ann., 1888, 245, p. 103). In this formula, the so-called “centric formula,” the assumption made is that the fourth valencies are simply directed towards the centre of the ring; nothing further is said about the fourth valencies except that they exert a pressure towards the centre. Claus maintained that Baeyer’s view was identical with his own, for as in Baeyer’s formula, the fourth valencies have a different function from the peripheral valencies, being united at the centre in a form of potential union.

It is difficult to determine which configuration most accurately explains the observed facts; Kekulé’s formula undoubtedly explains the synthetical production of benzenoid compounds most satisfactorily, and W. Marckwald (Ann., 1893, 274, p. 331; 1894, 279, p. 14) has supported this formula from considerations based on the syntheses of the quinoline ring. Further researches by Baeyer, and upon various nitrogenous ring systems by E. Bamberger (a strong supporter of the centric formula), have shown that the nature of the substituent groups influences the distribution of the fourth valencies; therefore it may be concluded that in compounds the benzene nucleus appears to be capable of existence in two tautomeric forms, in the sense that each particular derivative possesses a definite constitution. The benzene nucleus presents a remarkable case, which must be considered in the formulation of any complete theory of valency. From a study of the reduction of compounds containing two ethylenic bonds united by a single bond, termed a “conjugated system,” E. Thiele suggested a doctrine of “partial valencies,” 57 which assumes that in addition to the ordinary valencies, each doubly linked atom has a partial valency, by which the atom first interacts. When applied to benzene, a twofold conjugated system is suggested in which the partial valencies of adjacent atoms neutralize, with the formation of a potential double link. The stability of benzene is ascribed to this conjugation.14

Physico-chemical properties have also been drawn upon to decide whether double unions are present in the benzene complex; but here the predilections of the observers Physico-chemical methods. apparently influence the nature of the conclusions to be drawn from such data. It is well known that singly, doubly and trebly linked carbon atoms affect the physical properties of substances, such as the refractive index, specific volume, and the heat of combustion; and by determining these constants for many substances, fairly definite values can be assigned to these groupings. The general question of the relation of the refractive index to constitution has been especially studied by J.W. Brühl, who concluded that benzene contained 3 double linkages; whereas, in 1901, Pellini (Gazetta, 31, i. p. 1) calculated that 9 single linkages were present. A similar contradiction apparently exists with regard to the specific volume, for while benzene has a specific volume corresponding to Claus’ formula, toluene, or methylbenzene, rather points to Kekulé’s. The heat of combustion, as first determined by Julius Thomsen, agreed rather better with the presence of nine single unions. His work was repeated on a finer scale by M.P.E. Berthelot of Paris, and F.C.A. Stohmann of Leipzig; and the new data and the conclusions to be drawn from them formed the subject of much discussion, Brühl endeavouring to show how they supported Kekulé’s formula, while Thomsen maintained that they demanded the benzene union to have a different heat of combustion from the acetylene union. Thomsen then investigated heats of combustion of various benzenoid hydrocarbons—benzene, naphthalene, anthracene, phenanthrene, &c.—in the crystallized state. It was found that the results were capable of expression by the empirical relation CaH2b = 104.3b + 49.09m + 105.47n, where CaH2b denotes the formula of the hydrocarbon, m the number of single carbon linkings and n the number of double linkings, m and n being calculated on the Kekulé formulae. But, at the same time, the constants in the above relation are not identical with those in the corresponding relation empirically deduced from observations on fatty hydrocarbons; and we are therefore led to conclude that a benzene union is considerably more stable than an ethylene union.

Mention may be made of the absorption spectrum of benzene. According to W.N. Hartley (J.C.S., 1905, 87, p. 1822), there are six bands in the ultra-violet, while E.C.C. Baly and J.N. Collie (J.C.S., 1905, 87, p. 1332; 1906, 89, p. 524) record seven. These bands are due to molecular oscillations; Hartley suggests the carbon atoms to be rotating and forming alternately single and double linkages, the formation of three double links giving three bands, and of three single links another three; Baly and Collie, on the other hand, suggest the making and breaking of links between adjacent atoms, pointing out that there are seven combinations of one, two and three pairs of carbon atoms in the benzene molecule.

Stereo-chemical Configurations.—Simultaneously with the discussions of Kekulé, Ladenburg, Claus, Baeyer and others as to the merits of various plane formulae of the benzene complex, there were published many suggestions with regard to the arrangement of the atoms in space, all of which attempted to explain the number of isomers and the equivalence of the hydrogen atoms. The development of stereo-isomerism at the hands of J. Wislicenus, Le Bel and van ’t Hoff has resulted in the introduction of another condition which formulae for the benzene complex must satisfy, viz. that the hydrogen atoms must all lie in one plane. The proof of this statement rests on the fact that if the hydrogen atoms were not co-planar, then substitution derivatives (the substituting groups not containing asymmetric carbon atoms) should exist in enantiomorphic forms, differing in crystal form and in their action on polarized light; such optical antipodes have, however, not yet been separated. Ladenburg’s prism formula would give two enantiomorphic ortho-di-substitution derivatives; while forms in which the hydrogen atoms are placed at the corners of a regular octahedron would yield enantiomorphic tri-substitution derivatives.

Condensed Nuclei.

Restricting ourselves to compounds resulting from the fusion of benzene rings, we have first to consider naphthalene, C10H8, which consists of two benzene rings having a pair of carbon atoms in common. The next members are the isomers anthracene and phenanthrene, C14H10, formed from three benzene nuclei. Here we shall only discuss the structure of these compounds in the light of the modern benzene theories; reference should be made 58 to the articles Naphthalene, Anthracene and Phenanthrene for syntheses, decompositions, &c.

Naphthalene.—Of the earlier suggestions for the constitution of naphthalene we notice the formulae of Wreden (1) and (2), Berthelot and Balls (3), R.A.C.E. Erlenmeyer (4) and Adolf Claus (5).

The first suggestion is quite out of the question. C. Graebe in 1866 (Ann. 149, p. 20) established the symmetry of the naphthalene nucleus, and showed that whichever half of the molecule be oxidized the same phthalic acid results. Therefore formula (2), being unsymmetrical, is impossible. The third formula is based on Dewar’s benzene formula, which we have seen to be incorrect. Formula (4) is symmetrical and based on Kekulé’s formula: it is in full accord with the syntheses and decompositions of the naphthalene nucleus and the number of isomers found. In 1882 Claus suggested a combination of his own and Dewar’s benzene formulae. This is obviously unsymmetrical, consisting of an aliphatic and an aromatic nucleus; Claus explained the formation of the same phthalic acid from the oxidation of either nucleus by supposing that if the aromatic group be oxidized, the aliphatic residue assumes the character of a benzene nucleus. Bamberger opposed Claus’ formula on the following grounds:—The molecule of naphthalene is symmetrical, since 2.7 dioxynaphthalene is readily esterified by methyl iodide and sulphuric acid to a dimethyl ether; and no more than two mono-substitution derivatives are known. The molecule is aromatic but not benzenoid; however, by the reduction of one half of the molecule, the other assumes a benzenoid character.

It remains, therefore, to consider Erlenmeyer’s formula and those derived from the centric hypothesis. The former, based on Kekulé’s symbol for benzene, explains the decompositions and syntheses of the ring, but the character of naphthalene is not in keeping with the presence of five double linkages, although it is more readily acted upon than benzene is. On the centric hypothesis two formulae are possible: (i) due to H.E. Armstrong, and (2) due to E. Bamberger.

In the first symbol it is assumed that one of the affinities of each of the two central carbon atoms common to the two rings acts into both rings, an assumption involving a somewhat wide departure from all ordinary views as to the manner in which affinity acts. This symbol harmonizes with the fact that the two rings are in complete sympathy, the one responding to every change made in the other. Then, on account of the relatively slight—because divided—influence which would be exercised upon the two rings by the two affinities common to both, the remaining four centric affinities of each ring would presumably be less attracted into the ring than in the case of benzene; consequently they would be more active outwards, and combination would set in more readily. When, as in the formation of naphthalene tetrachloride, for example, the one ring becomes saturated, the other might be expected to assume the normal centric form and become relatively inactive. This is absolutely the case. On the other hand, if substitution be effected in the one ring, and the affinities in that ring become attracted inwards, as apparently happens in the case of benzene, the adjoining ring should become relatively more active because the common affinities would act less into it. Hence, unless the radical introduced be one which exercises a special attractive influence, substitution should take place in preference in the previously unsubstituted ring. In practice this usually occurs; for example, on further bromination, α-bromonaphthalene yields a mixture of the (1.4) and (1.5) dibromonaphthalenes; and when nitronaphthalene is either brominated, or nitrated or sulphonated, the action is practically confined to the second ring. The centric formula proposed by Bamberger represents naphthalene as formed by the fusion of two benzene rings, this indicates that it is a monocyclic composed of ten atoms of carbon. The formula has the advantage that it may be constructed from tetrahedral models of the carbon atom; but it involves the assumption that the molecule has within it a mechanism, equivalent in a measure to a system of railway points, which can readily close up and pass into that characteristic of benzene.

Anthracene and Phenanthrene.—These isomeric hydrocarbons, of the formula C14H10, are to be regarded as formed by the fusion of three benzenoid rings as represented by the symbols:—

In both cases the medial ring is most readily attacked; and various formulae have been devised which are claimed by their authors to represent this and other facts. According to Armstrong, anthracene behaves unsymmetrically towards substituents, and hence one lateral ring differs from the other; he represents the molecule as consisting of one centric ring, the remaining medial and lateral ring being ethenoid. Bamberger, on the other hand, extends his views on benzene and naphthalene and assumes the molecule to be (1). For general purposes, however, the symbol (2), in which the lateral rings are benzenoid and the medial ring fatty, represents quite adequately the syntheses, decompositions, and behaviour of anthracene.

Phenanthrene is regarded by Armstrong as represented by (3), the lateral rings being benzenoid, and the medial ring fatty; Bamberger, however, regards it as (4), the molecule being entirely aromatic. An interesting observation by Baeyer, viz. that stilbene, C6H5·CH:CH·C6H5, is very readily oxidized, while phenanthrene is not, supports, in some measure, the views of Bamberger.

Heterocyclic Compounds.

During recent years an immense number of ringed or cyclic compounds have been discovered, which exhibit individual characters more closely resembling benzene, naphthalene, &c. than purely aliphatic substances, inasmuch as in general they contain double linkages, yet withstand oxidation, and behave as nuclei, forming derivatives in much the same way as benzene. By reduction, the double linkages become saturated, and compounds result which stand in much about the same relation to the original nucleus as hexamethylene does to benzene. In general, therefore, it may be considered that the double linkages are not of exactly the same nature as the double linkage present in ethylene and ethylenoid compounds, but that they are analogous to the potential valencies of benzene. The centric hypothesis has been applied to these rings by Bamberger and others; but as in the previous rings considered, the ordinary 59 representation with double and single linkages generally represents the syntheses, decompositions, &c.; exceptions, however, are known where it is necessary to assume an oscillation of the double linkage. Five- and six-membered rings are the most stable and important, the last-named group resulting from the polymerization of many substances; three- and four-membered rings are formed with difficulty, and are easily ruptured; rings containing seven or more members are generally unstable, and are relatively little known. The elements which go to form heterocyclic rings, in addition to carbon, are oxygen, sulphur, selenium and nitrogen. It is remarkable that sulphur can replace two methine or CH groups with the production of compounds greatly resembling, the original one. Thus benzene, (CH)6, gives thiophene, (CH)4S, from which it is difficultly distinguished; pyridine, (CH)5N, gives thiazole, (CH)3·N·S, which is a very similar substance; naphthalene gives thionaphthen, C8H6S, with which it shows great analogies, especially in the derivatives. Similarly a CH group may be replaced by a nitrogen atom with the production of compounds of similar stability; thus benzene gives pyridine, naphthalene gives quinoline and isoquinoline; anthracene gives acridine and α and β anthrapyridines. Similarly, two or more methine groups may be replaced by the same number of nitrogen atoms with the formation of rings of considerable stability.

Heterocyclic rings may be systematically surveyed from two aspects: (1) by arranging the rings with similar hetero-atoms according to the increasing number of carbon atoms, the so-called “homologous series”; or (2) by first dividing the ring systems according to the number of members constituting the ring, and then classifying these groups according to the nature of the hetero-atoms, the so-called “isologous series.” The second method possesses greater advantages, for rings of approximate stability come in one group, and, consequently, their derivatives may be expected to exhibit considerable analogies.

As a useful preliminary it is convenient to divide heterocyclic ring systems into two leading groups: (1) systems resulting from simple internal dehydration (or similar condensations) of saturated aliphatic compounds—such compounds are: the internal anhydrides or cyclic ethers of the glycols and thioglycols (ethylene oxide, &c.); the cyclic alkyleneimides resulting from the splitting off of ammonia between the amino groups of diamino-paraffins (pyrrolidine, piperazine, &c.); the cyclic esters of oxycarboxylic acids (lactones, lactides); the internal anhydrides of aminocarboxylic acids (lactams, betaines); cyclic derivatives of dicarboxylic acids (anhydrides, imides, alkylen-esters, alkylen-amides, &c.). These compounds retain their aliphatic nature, and are best classified with open-chain compounds, into which, in general, they are readily converted. (2) Systems which are generally unsaturated compounds, often of considerable stability, and behave as nuclei; these compounds constitute a well-individualized class exhibiting closer affinities to benzenoid substances than to the open-chain series.

True ring systems, which possess the characters of organic nuclei, do not come into existence in three-and four-membered rings, their first appearance being in penta-atomic rings. The three primary members are furfurane, thiophene and pyrrol, each of which contains four methine or CH groups, and an oxygen, sulphur and imido (NH) member respectively; a series of compounds containing selenium is also known. The formulae of these substances are:

By substituting one or more CH groups in these compounds by nitrogen atoms, ring-systems, collectively known as azoles, result. Obviously, isomeric ring-systems are possible, since the carbon atoms in the original rings are not all of equal value. Thus furfurane yields the following rings by the introduction of one and two nitrogen atoms:

Thiophene yields a similar series: isothiazole (only known as the condensed ring, isobenzothiazole), thiazole, diazosulphides, piazthioles, azosulphimes and thiobiazole (the formulae are easily derived from the preceding series by replacing oxygen by sulphur). Thiophene also gives rise to triazsulphole, three nitrogen atoms being introduced. Selenophene gives the series: selenazole, diazoselenide and piaselenole, corresponding to oxazole, diazo-oxides and furazane. Pyrrol yields an analogous series: pyrazole, imidazole or glyoxaline, azimide or osotriazole, triazole and tetrazole:

Six-membered ring systems can be referred back, in a manner similar to the above, to pyrone, penthiophene and pyridine, the substances containing a ring of five carbon atoms, and an oxygen, sulphur and nitrogen atom respectively. As before, only true ring nuclei, and not internal anhydrides of aliphatic compounds, will be mentioned. From the pyrone ring the following series of compounds are derived (for brevity, the hydrogen atoms are not printed):

Penthiophene gives, by a similar introduction of nitrogen atoms, penthiazoline, corresponding to meta-oxazine, and para-thiazine, 60 corresponding to paroxazine (para-oxazine). Pyridine gives origin to: pyridazine or ortho-diazine, pyrimidine or meta-diazine, pyrazine or para-diazine, osotriazine, unsymmetrical triazine, symmetrical triazine, osotetrazone and tetrazine. The skeletons of these types are (the carbon atoms are omitted for brevity):

We have previously referred to the condensation of heterocyclic ring systems containing two vicinal carbon atoms with benzene, naphthalene and other nuclei. The more important nuclei of this type have received special and non-systematic names; when this is not the case, such terms as phen-, benzo-, naphtho- are prefixed to the name of the heterocyclic ring. One or two benzene nuclei may suffer condensation with the furfurane, thiophene and pyrrol rings, the common carbon atoms being vicinal to the hetero-atom. The mono-benzo-derivatives are coumarone, benzothiophene and indole; the dibenzo-derivatives are diphenylene oxide, dibenzothiophene or diphenylene sulphide, and carbazole. Typical formulae are (R denoting O, S or NH):

Isomers are possible, for the condensation may be effected on the two carbon atoms symmetrically placed to the hetero-atom; these isomers, however, are more of the nature of internal anhydrides. Benz-oxazoles and -thiazoles have been prepared, benz-isoxazoles are known as indoxazenes; benzo-pyrazoles occur in two structural forms, named indazoles and isindazoles. Derivatives of osotriazol also exist in two forms—azimides and pseudo-azimides.

Proceeding to the six-membered hetero-atomic rings, the benzo-, dibenzo- and naphtho-derivatives are frequently of great commercial and scientific importance, α-pyrone condenses with the benzene ring to form coumarin and isocoumarin; benzo-γ-pyrone constitutes the nucleus of several vegetable colouring matters (chrysin, fisetin, quercetin, &c., which are derivatives of flavone or phenyl benzo-γ-pyrone); dibenzo-γ-pyrone is known as xanthone; related to this substance are fluorane (and fluorescein), fluorone, fluorime, pyronine, &c. The pyridine ring condenses with the benzene ring to form quinoline and isoquinoline; acridine and phenanthridine are dibenzo-pyridines; naphthalene gives rise to α- and β-naphthoquinolines and the anthrapyridines; anthracene gives anthraquinoline; while two pyridine nuclei connected by an intermediate benzene nucleus give the phenanthrolines. Naphthyridines and naphthinolines result from the condensation of two pryridine and two quinoline nuclei respectively; and quino-quinolines are unsymmetrical naphthyridine nuclei condensed with a benzene nucleus. Benzo-orthoxazines, -metoxazines and -paroxazines are known: dibenzoparoxazine or phenoxazine is the parent of a valuable series of dyestuffs; dibenzoparathiazine or thiodiphenylamine is important from the same aspect. Benzo-ortho-diazines exist in two structural forms, cinnolin and phthalazine; benzo-meta-diazines are known as quinazolines; benzo-para-diazines are termed quinoxalines; the dibenzo-compounds are named phenazines, this last group including many valuable dyestuffs—indulines, safranines, &c. In addition to the types of compounds enumerated above we may also notice purin, tropine and the terpenes.

V. ANALYTICAL CHEMISTRY

This branch of chemistry has for its province the determination of the constituents of a chemical compound or of a mixture of compounds. Such a determination is qualitative, the constituent being only detected or proved to be present, or quantitative, in which the amount present is ascertained. The methods of chemical analysis may be classified according to the type of reaction: (1) dry or blowpipe analysis, which consists in an examination of the substance in the dry condition; this includes such tests as ignition in a tube, ignition on charcoal in the blowpipe flame, fusion with borax, microcosmic salt or fluxes, and flame colorations (in quantitative work the dry methods are sometimes termed “dry assaying”); (2) wet analysis, in which a solution of the substance is treated with reagents which produce specific reactions when certain elements or groups of elements are present. In quantitative analysis the methods can be subdivided into: (a) gravimetric, in which the constituent is precipitated either as a definite insoluble compound by the addition of certain reagents, or electrolytically, by the passage of an electric current; (b) volumetric, in which the volume of a reagent of a known strength which produces a certain definite reaction is measured; (c) colorimetric, in which the solution has a particular tint, which can be compared with solutions of known strengths.

Historical.—The germs of analytical chemistry are to be found in the writings of the pharmacists and chemists of the iatrochemical period. The importance of ascertaining the proximate composition of bodies was clearly realized by Otto Tachenius; but the first systematic investigator was Robert Boyle, to whom we owe the introduction of the term analysis. Boyle recognized many reagents which gave precipitates with certain solutions: he detected sulphuric and hydrochloric acids by the white precipitates formed with calcium chloride and silver nitrate respectively; ammonia by the white cloud formed with the vapours of nitric or hydrochloric acids; and copper by the deep blue solution formed by a solution of ammonia. Of great importance is his introduction of vegetable juices (the so-called indicators, q.v.) to detect acids and bases. During the phlogistic period, the detection of the constituents of compounds was considerably developed. Of the principal workers in this field we may notice Friedrich Hoffmann, Andreas Sigismund Marggraf (who detected iron by its reaction with potassium ferrocyanide, and potassium and sodium by their flame colorations), and especially Carl Scheele and Torbern Olof Bergman. Scheele enriched the knowledge of chemistry by an immense number of facts, but he did not possess the spirit of working systematically as Bergman did. Bergman laid the foundations of systematic qualitative analysis, and devised methods by which the metals may be separated into groups according to their behaviour with certain reagents. This subdivision, which is of paramount importance in the analysis of minerals, was subsequently developed by Wilhelm August Lampadius in his Handbuch zur chemischen Analyse der Mineralien (1801) and by John Friedrich A. Göttling in his Praktische Anleitung zur prüfenden und zurlegenden Chemie (1802).

The introduction of the blowpipe into dry qualitative analysis by Axel Fredrik Cronstedt marks an important innovation. The rapidity of the method, and the accurate results which it gave in the hands of a practised experimenter, led to its systematization by Jöns Jakob Berzelius and Johann Friedrich Ludwig Hausmann, and in more recent times by K.F. Plattner, whose treatise Die Probirkunst mit dem Löthrohr is a standard work on the subject. Another type of dry reaction, namely, the flame coloration, had been the subject of isolated notices, as, for example, the violet flame of potassium and the orange flame of sodium observed by Marggraf and Scheele, but a systematic account was wanting until Cartmell took the subject up. His results (Phil. Mag. 16, p. 382) were afterwards perfected by Robert Wilhelm Bunsen and Gustav Merz. Closely related to the flame-colorations, we have to notice the great services rendered by the spectroscope to the detection of elements. Rubidium, caesium, thallium, indium and gallium were first discovered by means of this instrument; the study of the rare earths is greatly facilitated, and the composition of the heavenly bodies alone determinable by it.

Quantitative chemistry had been all but neglected before the time of Lavoisier, for although a few chemists such as Tachenius, Bergman and others had realized the advantages which would accrue from a knowledge of the composition of 61 bodies by weight, and had laid down the lines upon which such determinations should proceed, the experimental difficulties in making accurate observations were enormous, and little progress could be made until the procedure was more accurately determined. Martin Heinrich Klaproth showed the necessity for igniting precipitates before weighing them, if they were not decomposed by this process; and he worked largely with Louis Nicolas Vauquelin in perfecting the analysis of minerals. K.F. Wenzel and J.B. Richter contributed to the knowledge of the quantitative composition of salts. Anton Laurent Lavoisier, however, must be considered as the first great exponent of this branch of chemistry. He realized that the composition by weight of chemical compounds was of the greatest moment if chemistry were to advance. His fame rests upon his exposition of the principles necessary to chemistry as a science, but of his contributions to analytical inorganic chemistry little can be said. He applied himself more particularly to the oxygen compounds, and determined with a fair degree of accuracy the ratio of carbon to oxygen in carbon dioxide, but his values for the ratio of hydrogen to oxygen in water, and of phosphorus to oxygen in phosphoric acid, are only approximate; he introduced no new methods either for the estimation or separation of the metals. The next advance was made by Joseph Louis Proust, whose investigations led to a clear grasp of the law of constant proportions. The formulation of the atomic theory by John Dalton gave a fresh impetus to the development of quantitative analysis; and the determination of combining or equivalent weights by Berzelius led to the perfecting of the methods of gravimetric analysis. Experimental conditions were thoroughly worked out; the necessity of working with hot or cold solutions was clearly emphasized; and the employment of small quantities of substances instead of the large amounts recommended by Klaproth was shown by him to give more consistent results.

Since the time of Berzelius many experimenters have entered the lists, and introduced developments which we have not space to mention. We may, however, notice Heinrich Rose15 and Friedrich Wohler,16 who, having worked up the results of their teacher Berzelius, and combined them with their own valuable observations, exerted great influence on the progress of analytical chemistry by publishing works which contained admirable accounts of the then known methods of analysis. To K.R. Fresenius, the founder of the Zeitschrift für analytische Chemie (1862), we are particularly indebted for perfecting and systematizing the various methods of analytical chemistry. By strengthening the older methods, and devising new ones, he exerted an influence which can never be overestimated. His text-books on the subject, of which the Qualitative appeared in 1841, and the Quantitative in 1846, have a world-wide reputation, and have passed through several editions.

The quantitative precipitation of metals by the electric current, although known to Michael Faraday, was not applied to analytical chemistry until O. Wolcott Gibbs worked out the electrolytic separation of copper in 1865. Since then the subject has been extensively studied, more particularly by Alexander Classen, who has summarized the methods and results in his Quantitative Chemical Analysis by Electrolysis (1903). The ever-increasing importance of the electric current in metallurgy and chemical manufactures is making this method of great importance, and in some cases it has partially, if not wholly, superseded the older methods.

Volumetric analysis, possessing as it does many advantages over the gravimetric methods, has of late years been extensively developed. Gay Lussac may be regarded as the founder of the method, although rough applications had been previously made by F.A.H. Descroizilles and L.N. Vauquelin. Chlorimetry (1824), alkalimetry (1828), and the volumetric determination of silver and chlorine (1832) were worked out by Gay Lussac; but although the advantages of the method were patent, it received recognition very slowly. The application of potassium permanganate to the estimation of iron by E. Margueritte in 1846, and of iodine and sulphurous acid to the estimation of copper and many other substances by Robert Wilhelm Bunsen, marks an epoch in the early history of volumetric analysis. Since then it has been rapidly developed, particularly by Karl Friedrich Mohr and J. Volhard, and these methods rank side by side in value with the older and more tedious gravimetric methods.

The detection of carbon and hydrogen in organic compounds by the formation of carbon dioxide and water when they are burned was first correctly understood by Lavoisier, and as he had determined the carbon and hydrogen content of these two substances he was able to devise methods by which carbon and hydrogen in organic compounds could be estimated. In his earlier experiments he burned the substance in a known volume of oxygen, and by measuring the residual gas determined the carbon and hydrogen. For substances of a difficultly combustible nature he adopted the method in common use to-day, viz. to mix the substance with an oxidizing agent—mercuric oxide, lead dioxide, and afterwards copper oxide—and absorb the carbon dioxide in potash solution. This method has been improved, especially by Justus v. Liebig; and certain others based on a different procedure have been suggested. The estimation of nitrogen was first worked out in 1830 by Jean Baptiste Dumas, and different processes have been proposed by Will and F. Varrentrapp, J. Kjeldahl and others. Methods for the estimation of the halogens and sulphur were worked out by L. Carius (see below, § Organic Analysis).

Only a reference can be made in this summary to the many fields in which analytical chemistry has been developed. Progress in forensic chemistry was only possible after the reactions of poisons had been systematized; a subject which has been worked out by many investigators, of whom we notice K.R. Fresenius, J. and R. Otto, and J.S. Stas. Industrial chemistry makes many claims upon the chemist, for it is necessary to determine the purity of a product before it can be valued. This has led to the estimation of sugar by means of the polarimeter, and of the calorific power of fuels, and the valuation of ores and metals, of coal-tar dyes, and almost all trade products.

The passing of the Food and Drug Acts (1875-1899) in England, and the existence of similar adulteration acts in other countries, have occasioned great progress in the analysis of foods, drugs, &c. For further information on this branch of analytical chemistry, see Adulteration.

There exists no branch of technical chemistry, hygiene or pharmacy from which the analytical chemist can be spared, since it is only by a continual development of his art that we can hope to be certain of the purity of any preparation. In England this branch of chemistry is especially cared for by the Institute of Chemistry, which, since its foundation in 1877, has done much for the training of analytical chemists.

In the preceding sketch we have given a necessarily brief account of the historical development of analytical chemistry in its main branches. We shall now treat the different methods in more detail. It must be mentioned here that the reactions of any particular substance are given under its own heading, and in this article we shall only collate the various operations and outline the general procedure. The limits of space prevent any systematic account of the separation of the rare metals, the alkaloids, and other classes of organic compounds, but sources where these matters may be found are given in the list of references.

Qualitative Inorganic Analysis.

The dry examination of a substance comprises several operations, which may yield definite results if no disturbing element is present; but it is imperative that any inference Dry methods. should be confirmed by other methods.

1. Heat the substance in a hard glass tube. Note whether any moisture condenses on the cooler parts of the tube, a gas is evolved, a sublimate formed, or the substance changes colour.

2. Heat the substance on a piece of charcoal in the reducing flame of the blowpipe.

3. Heat the substance with a bead of microcosmic salt or borax on a platinum wire in the oxidizing flame.

4. Hold a small portion of the substance moistened with hydrochloric acid on a clean platinum wire in the fusion zone of the Bunsen burner, and note any colour imparted to the flame.

5. Film Reactions.—These reactions are practised in the following manner:—A thread of asbestos is moistened and then dipped in the substance to be tested; it is then placed in the luminous point of the Bunsen flame, and a small porcelain basin containing cold water placed immediately over the asbestos. The formation of a film is noted. The operation is repeated with the thread in the oxidizing flame.

Having completed the dry analysis we may now pass on to the wet and more accurate investigation. It is first necessary to get the substance into solution. Small portions Wet methods. should be successively tested with water, dilute hydrochloric acid, dilute nitric acid, strong hydrochloric acid, and a mixture of hydrochloric and nitric acids, first in the cold and then with warming. Certain substances are insoluble in all these reagents, and other methods, such as the fusion with sodium carbonate and potassium nitrate, and subsequent treatment with an acid, must be employed. Some of these insoluble compounds can be detected by their colour and particular reactions. For further information on this subject, we refer the readers to Fresenius’s Qualitative Analysis.