The _Metals_, _chemically_ regarded, do not admit of being separated into constituent parts. They exhibit only physical differences in gravity, colour, hardness, malleability, conducting power, tension or their mutual polarity. If it be endeavoured to arrange them according to these respects, nothing but disorder results. The same is the case in reference to their affinity for oxygen, sulphur, the acids and other metals. Rather more order is at once displayed if their philosophical composition, namely as carbon and fire, be submitted to our consideration.
508. In consequence of this view, the _Metals_ must divide into Earth-metals and Fire-metals; and the latter again into three subdivisions, nearly as follows:--
A. Earth-metals--difficultly fusible and invariably oxydized--Sidereometalla, e. g. Iron--Manganese, Wolfram, Uranium, Titanium, Chromium, &c.
a. Heavy metals; difficultly fusible, unoxydized or noble metals, e. g. Platinum, Nickel, Cobalt.
b. Light metals; the easily fused noble metals--e. g. Gold, Silver, &c.
c. Heat-metals; the easily fused, ignoble and frequently volatile metals, e. g. Lead, Tin, Antimony, Zinc, Arsenic, &c.
509. The _Inflammables_ divide under a chemical point of view into two groups--into the varieties of Coal and Sulphur, whereof the Earthy lies at the basis of the former which is non-fusible; the Aerial at that of the latter. They do not admit of being divided, unless a mean betwixt the two be taken, the combinations of carbon and hydrogen in the resins.
510. The _Salts_ admit of a better dismemberment. Their constituent parts are alkalies and acids, the former the Earthy, the latter the Aqueous. The mean condition is exhibited by the neutral salts, so that three orders are the result.
511. Now by the philosophical view we have first attained to the very remarkable import of the acids. They are forsooth nothing else than oxydized elements and mineral classes. In the nitric acid it is evident that, as the acid of nitrogen, it is the _aerial acid_; as sulphuric acid is the _inflammable acid_; arsenic acid the _metallic acid_. Upon this ground we may expect that the other acids also have a similar origin. Without much hesitation hydrochloric acid may be viewed as the _aqueous acid_, which is associated with the sea; the carbonic acid as _æther-_ or _igneous-acid_, as well on account of its constituent parts and gaseous character, as chiefly on account of its general diffusion. There remain then only two that have been called mineral acids, the fluoric and boracic acids, the first of which, as conqueress of the earths is the _earth acid_, the last being thus the acid of the _salts_. We have accordingly--