METALS AND ALLOYS.

Metals may be known from all other substances by certain properties: they have that peculiar brilliancy, called, for that reason, the “metallic” lustre; they are rapidly heated, and as rapidly cool, hence they are said to be good conductors of heat; they are all opaque, and most of them very heavy; some indeed, as gold and platinum, are the heaviest substances known, being about twenty times heavier than water; they have, moreover, other valuable properties such as the capability of being melted, of being drawn out into wire, of being beaten into thin plates, &c.

All metals are simple bodies; that is to say, they cannot be made out of other substances, although two or more metals may be combined and be again separated, or they may be combined with numerous other substances, as oxygen, and also again separated. There are upwards of fifty metals known to chemists, yet but few are used to any extent in the arts or manufactures. All the metals in use for the very many purposes to which they are applied are not simple metals, but are what are called “alloys,” that is to say, compounds of two or more metals. The chief metals in use are—

But in the state of oxide many are used which are seldom seen in the metallic state, such are the earths and alkalies; and for colors, and several other purposes, many other preparations are in use. The chief alloys, or compound metals in use, are, brass, made of copper and zinc; pewter, made of lead and tin; bell metal and gun metal, made of copper and tin; and solder, which is a kind of pewter, and made of the same metals; the silvering for looking-glasses is made of mercury and tin; the gold and silver used for coin are not pure metals, but alloyed with two parts of silver or copper to every twenty-two of the pure metal, and this forms the “standard” gold or silver. The gold used by jewellers has often a much greater proportion of alloy—for this name is given both to a compound metal