A yellow metal of specific gravity 19.3, which is greater than any other body in nature, except platina. It is soft, very tough, ductile, and malleable, unalterable and fixed, whether in the atmosphere or in the heat of the hottest furnaces; but it has been volatilized by powerful burning mirrors, as also by the oxy-hydrogen blow pipe. No acid acts readily upon gold, except the nitro-muriatic acid, called aqua regia, in which it may be dissolved, occasioning at the same time an effervescence; but from the slight affinity of gold for oxygen, it is precipitated from its solvent by the alkalies, earths, and most of the other metals. Its precipitate with ammonia forms a compound, which detonates with great violence, as has been already mentioned under the article Fulminating Powders. Most metals combine with gold, increasing its hardness, but considerably impairing its ductility. For the purposes of coin, Mr. Hatchett considers an alloy of silver and copper in equal parts to be preferred, and copper alone as preferable to silver only: but the gold coins of Great Britain are composed of eleven parts of gold, and one of copper.
Gold is mostly found in the metallic state, although generally combined with silver, copper, or iron, or all three.
It is found either in separate lumps or visible grains amongst the sands of rivers, in many parts of Europe, and elsewhere. The quantity is for the most part insufficient to pay the expense of separating it; but it is thought to be more universally diffused in sands and earth than any other metal, except iron. Some sands afford gold by simple washing, the heavy metallic particles subsiding first; but when it is imbedded in earths and stones, these substances are first pounded, and then boiled with one tenth of their weight of mercury, together with water. The mercury after a certain time forms an amalgam with the gold, from which it is separated by pressure through leather bags, and subsequent distillation. Gold is seldom used for any purpose in a state of perfect purity. In estimating its fineness, the whole mass spoken of is supposed to weigh 24 carats, of 12 grains each, and the pure gold is called fine: Thus, if gold is said to be 23 carats fine, it is understood that the mass consists of 23 parts of fine gold, and one part of alloy.