Page:Encyclopædia Britannica, Ninth Edition, v. 5.djvu/472

460 CHEMISTRY [HISTORY. Among the contemporaries but not the followers of Paracelsus, the German metallurgist Agricola (1494-1555) deserves mention ; his great work, De He Metallica, is the most valuable contribution to practical chemistry that appeared in the 16th century. Libavius also, who died in 1616, did much to forward chemical science at this period. From his writings, however, in which he puts forward the views both of Paracelsus and of Aristotle concerning the constitution of bodies, it does not appear that his notions of chemical combination were more definite than those of his predecessors. J. B. Van Helmont (1577-1644), who, like Paracelsus, repudiated the doctrines of the Galenists, held opinions that in many respects were no advance upon those of the former. He looked upon water as the true principle of all existing things, inclusive of the three principles salt, sul phur, arid mercury, which therefore were not elements ; to air, however, he granted the rank of a true element. The arc/iceus -something without form, and independent of the elements he imagined to draw all bodies from water, to which its generating spirit was attracted by the odour of a ferment or aura vitalis. The vapour produced by the fermentation of water was, according to Van Helmont, a gas, and the same term was by him for the first time applied to carbon dioxide, which he termed gas sylvestre, and to other bodies resembling air. To Francis de la Boe Sylvius (1614-1672), who studied with care the works of Van Helmont and of Descartes, is due the foundation of the iatro-cheroical sect among phy sicians. In liis view the health of the human frame depends upon the relation of its fluids, which were acid and alkaline (acidum and lixivum), and these by union produced a neutral and milder substance ; two kinds of diseases were distinguished, the result either of alkaline or of acid acridity. The new doctrine served to explain many chemical facts, and led to the establishment by Le"mery and Macquer of a distinction between acid and alkaline or, as they were afterwards called, basic compounds. This recognition of this chemical difference in bodies and their consequent disposition to unite prepared the way for the conception of chemical attraction or affinity. In the works of Glauber (1604-1668), alchemy, the preparation of chemical medicines, and the processes em ployed by him for that end are treated of. His Miraculum Mundi has for its subject the virtues of the sal mirabile, sulphate of sodium, or Glauber s salt, of which he was the discoverer ; and in other of his works he describes various chlorides of the metals, the sulphates of iron and copper, and sulphuric, nitric, and hydrochloric acids, but with respect to their ultimate constitution he advances no theory ; he variously states in his different works that mercury and salt are the principles of all metals, that salt is the origin of all things, and again that water and earth have pro duced all the minerals and metals. The first to attempt to overthrow the doctrines of the iatro-chemists was Robert Boyle (1627-1691), who in 1661 published the first edition of The Sceptical Chemist, or Ghy mica-Physical Doubts and Paradoxes touching the Experiments -whereby vulgar Spagyrists are wont to endeavour to evince their Salt, Sulphur, and Mercury to be t/ie true Principles of Things, a treatise in which he shows the doubtful character of the doctrine of the threefold con stitution of matter, and lays stress upon the influence of heat in the formation of new bodies, not necessarily pre- existent as such in the substances from which they are pro duced. If, as he tells us, he is somewhat too indulgent of suspicion against the hypotheses or arguments of other chemists, he is only acting in compliance with the advice nf Aristotle, and betiding a crooked stick the contrary way, ! to reduce it at length to straighcness. Into the mouth of j " Themistius " he puts the complaint that " Aristotle s hypo thesis had not been called in question till in the last cen tury Paracelsus and some few other sooty empiricks, having their eyes darkened and their brains troubled with the smoke of their furnaces, began to rail at the Peripatetick doctrine, which they were too illiterate to understand, and to tell the credulous world that they could see the three ingredients in mixed bodies, which, to gain themselves the repute of inventors, they endeavoured to disguise by calling them instead of earth, and fire, and vapour salt, sulphur, and mercury, to which they gave the canting title of hypostatical principles." Boyle inclines to a belief in " but one universal matter of things, as it is known that the Aristotelians themselves acknowledge, who called it materiel prima ; the portions of this matter seem to difl er from one another in certain qualities or accidents, fewer or more." He thinks that elementary corpuscles are of various sizes, and of more sorts than three or four or five; and that the combination of two of these corpuscles may give rise to a new body as really one as either of the cor puscles before they were mingled or confounded, this con cretion being endowed with distinct qualities, and no more by fire or any known way of analysis divisible into the corpuscles that had first concurred to make it, than either of them could by the same means be subdivided into other particles. He furthermore deduces from his arguments the corollary, " That it may as yet be doubted whether or no there be any determinate number of elements ; or, if you please, whether or no all compound bodies do consist of the same number of elementary ingredients or material prin ciples." In another work, The Imperfections of the Chemical Doctrine of Qualities, Boyle points out the arbitrary nature of Sylvius s classification of all substances as acids and alkalies, and the needlessness and unsatisfactory character of his hypotheses. latro-chemistry was opposed also by Conring (1606-1681), Sydenham (1624-1689), Pitcairne (1652-1713), and his pupil Boerhaave (1668-1738), the author of the excellent Elementa Chemice ; and though vig orously supported by De Blegny, Borrichius, Viridet, Vieussens, and others, it gradually lost repute, and was finally overthrown by F. Hoffmann (1660-1742). Of the labours of Kunckel (1630-1703) in the cause of chemistry it is impossible to give an account within the corn- pass of the present sketch ; but whilst the science was en riched by means of his numerous researches, amongst which may be mentioned those on phosphorus, it received DO assistance from his theoretical views concerning the consti tution of bodies ; thus, for instance, he rejected the belief in the three principles of Paracelsus, yet maintained that all metals contained common quicksilver ; and though their increase in weight by calcination was not, according to him, due to the absorption of ponderable fiery material, the explanation he offered of this phenomenon was even less satisfactory. To Becher (1635-1682) and to Stahl (1660-1734) chemistry owes the introduction of the first consistent theory of the constitution of compounds and of chemical action. Becher held that the primary ingredients of matter were water and earth, and that from these were produced three earths the fusible or stony, the fatty, and the fluid earths, improperly called salt, sulphur, and mer cury. Stahl, who developed the doctrines of Becher, enumerated four elements water, acid, earth, and phlogiston. Becher had explained the calcination of metals on the supposition that they consisted of an earth and a some thing of which they became deprived on ignition ; the burning of brimstone was, in like manner, thought to be its resolution into an acid and true sulphur, or that combus tible part which was dispelled by heat. It was this

supposed combustible body to which the name phlogiston