GOLD. This costly and beautiful metal has been known from the remotest antiquity, and has been un versally employed as a me dium of exchange. Although the quantity of gold which is found, when compared with that of other metals, is small, yet it occurs in greater or less abundance in almost every part of the globe. It occurs in the na tive state, and combined with silver, and frequently mixed with metallic sulphurets and arseniurets. The greatest quantity of gold, next to that recently discovered in California, is the produce of South America ; the richest mines of Europe are those in Hungary, and %ft Asia, in Siberia ; it has been found also in the sands of the RhOne, the Rhine, and the Danube ; small quantities are occasionally found in the stream tin-works of Cornwall, in Wicklow in Ireland, and in the Lead Hills in Scotland. In 1826 one piece of native gold was found in Siberia weighing 26 lbs.
Native gold occurs crystallised, capillary, and massive; the primary form is a cube. Gold not unfrequently occurs alloyed with silver, and this compound, where the quantity of silver is considerable, is known by the name of electrum. Gold is separated from the various substances with which it is mixed by the process of amalgamation ; this consists in com bining it with mercury, and heating the amal. gam formed, so as to distil the mercury, which is thus repeatedly used for the same purpose.
Gold is of a fine yellow colour, and is sus ceptible of a high degree of polish. It is nearly as soft as lead. For its malleability, see GOLD-BEATING. It is also exceedingly ductile ; a single grain may be drawn out into 500 feet of wire. Gold suffers no change by exposure to air or moisture, even when heated. It melts at about 2016° of Fahr.,
according to Daniell's pyrometer ; when in fusion, it appears of a brilliant green colour.
Most metals are susceptible of combining with gold to form alloys, of which the follow ing are the chief. Arsenic and gold form a brittle gray substance. Tellurium and gold, but mixed with a considerable portion of lead, occur in combination, constituting three varieties known as graphic tellurium, yellow tellurium, and black tellurium. Antimony and gold form a pale yellow finely grained sub stance. Manganese and gold form a pale brittle alloy. Zinc and gold yield a pale green alloy, very brittle. Tin and gold form a pale yellow alloy, slightly flexible. Iron and gold form an alloy of a pale yellowish-gray colour ; it is very ductile, and may be rolled from the thickness of three-quarters of an inch to that of a guinea. Nickel and gold form a brittle yellow alloy ; as do Cobalt and gold. Copper and gold combine in all proportions, with little alteration of the colour of the gold ; the density is diminished, but the hardness is increased. Bismuth and gold form a brittle yellow alloy. Silver and gold combine well ; the resulting alloys are very ductile. Silver and copper are both used as alloys in gold coin. Lead and gold yield a very brittle alloy. Mercury and gold form an amalgam much used in the arts [AitALGAIT ; GILDING]. Pla tinum and gold form an alloy in which the colour of the gold is destroyed.
The Salts of Gold, formed by the combina tion of the metal with acids, are not much employed in the arts, and are mostly of an unstable character. A compound of gold with peroxide of tin forms the beautiful purple powder of Cassius.