CHEMISTRY
HISTORICAL INTRODUCTION.—The acquaintance of the ancients with the modes of extracting several of the metals from their ores, and also with the arts of dyeing, tanning, and glassmaking, and their recognition of various kinds of salts, earths, and inflammable sub stances show that they must have been possessed of a knowledge of a considerable number of chemical facts ; but that this knowledge was to any extent gained by experi mental research rather than by mere accident, or that when acquired it was applied to the classification of chemical phenomena, or to the establishment of any theory explan atory of them, there is no evidence to show. Until com paratively recent times the principles of metaphysical philosophy were not recognized as distinct from those of chemistry ; men of learning gave themselves up to specu lation upon the obvious physical characteristics of matter, whilst they neglected the indirect observation of their intrinsic and specific properties ; analogies were a sufficient basis for the classification of bodies, and a consideration of their external peculiarities " a decomposition of bodies," to use the words of Whewell, " into adjectives, not into substantives " stood in the place of analysis. Thus we find that the qualities of the " elements" of the school of Aristotle are all physical, they are dry or humid, warm or cold, light or heavy ; the idea of substances distinguished by special chemical properties was as yet no less foreign to men s minds than a knowledge of their ultimate com position.
Ideas similar to those of Aristotle concerning the elemen tary constitution of the universe were early prevalent in the East, whence they appear to have found their way into Europe. The elements, according to the Hindus, were earth, air, fire, water, and ether , and in the fourth book of " Chow, " forming part of the Chinese historical records known as the Shoo King, there is a document supposed to date from 2000 B.C., in which is given an account of the five elements, namely, earth, fire, water, metal, and wood. Of what precisely was meant by an "element" in the language of the ancient philosophers and early chemists it is difficult to get any definite idea ; the term could hardly, in fact, be used otherwise than in a vague sense before the exact processes of chemical analysis had shown that the properties of matter vary according to the presence or absence within it of definite quantities of certain sub stances, distinct in properties from one another, and un- resolvable into other substances
To the doctrine of a plurality of elements, as opposed to the systems of Thales and Heraclitus, may be ascribed the origin of the conception that by the analysis and synthesis of bodies the various kinds of matter with all their diversity of physical features might be produced, a conception that took practical shape in the processes of alchemy, which, as Liebig has remarked, " was never at any time different from chemistry." During the alchemistical period a knowledge of the properties of bodies was acquired ; afterwards chemistry showed the relations, connections, and limits of these properties. The first mention of chemistry (^/xft a) is found in the dictionary of Suidas, who flourished in the llth century; he defines it as "the preparation of silver and gold," and relates that Diocletian, lest the Egyptians should become rich and capable of resisting the Roman power, caused their books on chemistry to be burnt. He further asserts that the art was known as early as the period of the Argonautic expedition, the golden fleece being a treatise written on skins (Sep/mo-i) concerning the making of gold. The belief in the art of making gold and silver, held by the Greeks from the 5th to the 15th century, was by them communicated to the Arabs, possibly not long after the conquest of Egypt in 640 ; and from the llth to the 15th century alchemy was diligently studied by the philosophers of Italy, France, Germany, and England.
That the claims of alchemy, notwithstanding repeated demonstrations of their futility, so long received the serious attention of mankind, is attributable to various causes. Not only did impostors find free scope in the credulity of an age of ignorance for the exercise of their arts ; but men of talent and culture, relying on tradition, were led honestly to support the doctrine of the transmutation of metals. The existence of the philosopher s stone having once been accepted as an ascertained fact, it is not extra ordinary that Isaacus Hollandus is able to indicate the method of its preparation from !: adamic" or "virgin" earth, and its action when medicinally employed; that Roger Bacon, Raymond Lully, Basil Valentin, and John Price know the exact quantities of it to be used in trans mutation ; and that George Rippel, in the 15th century, has grounds for regarding its action as similar to that of a ferment. In the view of some alchemists, the ultimate prin ciples of matter were Aristotle s four elements, the proxi mate constituents were sulphur and 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. Geber, judging from an analogy instituted between the healthy human being and gold, the most perfect of the metals, regarded silver, mercury, copper, iron, lead, and tin in the light of lepers that required to be healed.
To the evidence of their imaginations the alchemists were able to add that of actual observation ; the fact that many ores resembling metals were changed and decom posed by heat could not but offer support to theories formed at a time when the nature of chemical combination was not understood ; and the apparent transition of many bodies into one another, as, for example, that of clouds into water, was not less wonderful to them than the transmutation of the lighter metals into gold.
It was in the 16th century that a new race of alchemists, or spagyrists, as they were termed, arose, who, abandoning the search for the philosopher s stone, began to direct their energies to the discovery of chemical remedies for the various diseases of the body. " The true use of chemistry," says Paracelsus (1493-1541) "is not to make gold, but to prepare medicines." Rejecting the teaching of Galen, he admitted three or four elements, the star, the root, the element, and the sperm or true seed, which were originally confounded together in the chaos or yliados ; these ele ments he asserted were composed of the three principles sideric salt and sulphur and mercury, the cause respectively of the qualities of fixity, combustibility, and fluidity and volatility. The theories of Paracelsus found many advo cates, amongst whom may be mentioned Thurneysser (1531-1596), Bodenstein, Taxites, Dora, Sennert, andDu- chesne ; and with some modifications they were main tained in the 17th century by Dr Willis (1621-1675), the celebrated English anatomist and iatro-chemist, and by Lefebvre and Le"mery in France, according to whose system matter consisted of the active principles mercury or spirit, sulphur or oil, and salt, and the passive principles water or phlegm and earth.
