Page:The American Cyclopædia (1879) Volume IV.djvu/365

 CHEMISTRY 357 it became so far developed as to deserve the name of science. Many chemical facts must have been known from the earliest times. As far back as history goes they are treated of. Only by the gradual collection and explanation of such facts could chemistry become a science. The Egyptians possessed considerable chemical knowledge. The smelting of ores and working of metals must have been brought to a high degree of perfection among them ; otherwise many of their works of art, still existing, could not have been made. Their skill in dyeing im- plies a knowledge of the necessary chemicals and mordants. They also made glass, even colored, and knew how to prevent the decom- position of dead animal matter. The priesthood evidently possessed more or less knowledge of pharmaceutical chemistry. The Phoenicians dyed, made glass, and imported tin. The Is- raelites seem to have obtained some chemical knowledge, especially relating to metallurgy, during their sojourn in Egypt ; they were ac- quainted with gold, silver, copper, tin, lead, and iron. The Greeks in the time of Homer seem to have had only what chemical knowledge they had derived from the Egyptians and Phoe- nicians. The metaphysical direction of the Greek mind was not calculated to advance the science by experimental investigations. They attempted, on the other hand, to explain the composition and origin of matter by philosophi- cal speculations, as seen in the discussions re- garding the elements, some five or six centuries before Christ. The views advanced by Aris- totle on this subject long exerted a great influ- ence on the science. He considered substances to be the result of the mixture of several funda- mental properties, and their components or ele- ments only as bearers of these properties, not at all as material, undecomposable substances which could be extracted experimentally. Ac- cording to Aristotle these properties are those evident to the senses, viz. : hot, cold, dry, wet, heavy, light, hard, soft, &c. He recognized only the first four of these, because the others are less general and for the most part only secondary results of the union of the preceding. Hence his conclusion that there are four fundamental properties, hot, cold, dry, and wet, which char- acterize the four elementary conditions of mat- ter, or elements, fire, air, earth, and water, of which all substances are composed, and from which their peculiarities are derived. He ad- mits that each element possesses two of these properties at the same time, and since no ele- ment can have at once two totally opposite pro- perties, cannot be simultaneously wet and dry, only four combinations are possible. Thus, si- multaneous dryness and heat form fire; heat and moisture, air ; cold and dryness, earth ; cold and moisture, water. The Eomans derived some chemical knowledge from other nations. They were acquainted with the metals previ- ously mentioned, also with mercury, the power of which to dissolve gold they made use of in gilding. They knew of various alloys, of steel, glass, vinegar, and soap. Their knowledge of dyeing was less than that possessed by the Egyptians. Although but little is known of the progress of chemistry from the 1st to the 4th century A. D., it is probable that much of the knowledge which had long been kept secret by the Egyptian priests was now published and taught at Alexandria. Previous to the latter period chemistry had consisted only of a collec- tion of empirical facts without intimate connec- tion or definite purpose, upon which no theo- retical views of any kind had been founded. It has been a peculiarity of chemistry, that while preserving its name and connection as a science it has had temporarily, at various times, special objects in view, to the attainment of which all its energies were directed for the time, while what is now regarded as the true aim of the science was used only as a means of obtaining the desired result. Such a period now com- menced. It was characterized by the purpose which the science served, as well as by a theory upon the composition of the metals. All chem- ical facts were now studied under a certain connection for the purpose of solving a given problem: how to convert base metals into no"ble, as iron or lead into silver or gold. This idea is first mentioned by Greek authors of the 4th century, who speak of it as a thing already well known. It probably originated with the Egyptians, from whom it passed to the Arabs when they overran Egypt in the Vth century. From the middle of the 8th century the Arabs paid much attention to chemistry. From them its study passed through Spain into northern Europe. The purpose was still the transmu- tation of metals, the discovery of the philoso- pher's stone, the touch of which would con- vert mercury into gold, and at a later period also regarded as capable of curing all dis- eases. The first chemical theory appears in the 8th century. It consisted essentially in this : All metals are composed of two constituents, upon the relative quantity and purity of which the nature of the metal depends. These com- ponents were called sulphur and mercury. Although not possessing all the properties of ordinary sulphur and mercury, they derived their names from these last, which were sup- posed to contain a large proportion of them, but their properties were nevertheless different. The sulphur and mercury of the alchemists must be regarded, therefore, as conventional elements, deriving their names from certain analogies which they bore to ordinary sulphur and mercury. By mercury, undecomposability appears to have been understood; it was also regarded as the cause of metallic lustre and of malleability ; by sulphur, on the contrary, de- composability was understood ; these terms re- ferring to the behavior of substances when subjected to fire, at that time regarded as the most powerful chemical agent. The various metals were supposed to be composed of these two bodies in different quantities, degrees of purity and of fixity (affinity?). The fusibility