HISTORICAL INTRODUCTION: Chemical Ideas in Ancient Greece, India, China
The acquaintance of the ancients with the modes of extracting several of the metals form their ores, and also with the arts of dyeing, tanning, and glassmaking, and their recognition of various kings of salts, earths, and inflammable substances 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 experimental 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 explanatory of them, there is no evidence to show. Until comparatively recent times the principles of metaphysical philosophy were not recognized as distinct from those of chemistry; men of learning gave themselves up to speculation 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 mens minds than a knowledge of their ultimate composition.
Ideas similar to those of Aristotle concerning the elementary 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 form 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 the certain substances, distinct in properties from one another, and unresolvable 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."
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