GOLD (AS:, OHG. gold, Ger. Gpld, Goth. gulp; connected with AS. geolu, Eng. yellow, Lat. helvus, grayish yellow, Gk. V.wpOg, chldros, yellowish green, Skt. hari, yellow). A metallic chemical element, probably the first metal known to man. The alchemists regarded gold as the most perfect metal, compared it to the sun, and designated it by the same symbol by which they represented that orb; their efforts were con stantly directed toward the transmutation of baser metals into pure gold. Gold is widely distributed in nature, and is frequently found native, though usually alloyed with silver and containing small quantities of copper or iron; it is also associated with palladium, rhodium, and bismuth. It is sometimes found crystallized, usually as octahedra or tetrahedra, but more commonly in thin lamina or grains in sand or gravel. Its presence in this condition is believed to have been caused by the disintegration of gold-bearing rocks, and it is readily collected from such alluvial sources by washing the au riferous soil. The purest specimens of native gold have yielded from 99.7 to 99.8 per cent. of the pure metal, the average ,California gold containing 88 per cent., while Australian gold sometimes runs as high as 96 per cent. pure metal. Gold also occurs in combination with mercury as electrum, with silver and tellurium as sylvanite, and with tellurium and lead as nagyagite. It is further found in various sul phides, as those of copper, lead, iron, and zinc; also in other ores, and in sea-water.
Gold (symbol, Au; atomic weight, 197.2) is
of a bright yellow color when pure, and has a high metallic lustre. It is the most malleable of all metals, and has been hammered into a leaf 0.00009 millimeter in thickness. In this condition it appears green by transmitted light. Gold is very ductile, and can be drawn into wire so fine that 166 meters weigh but a single gram. Its specific gravity is 19.31, and it melts at about 1075° C. It is a good conductor of both heat and electricity. Whatever the tem perature, neither water nor oxygen is capable of attacking it; and it is not affected by fusion with potassium chlorate. It yields, however, to alkalies and nitrates, and especially to sodium or potassium cyanide. It is not dissolved by any single acid, except selenic, but readily passes into solution when treated with aqua regia (a mix ture of nitric and hydrochloric acids), or with other acid liquids in which chlorine or bromine is evolved. Pure gold, being too soft for all ordinary purposes, is generally alloyed with other metals. With copper it yields a reddish alloy, which is quite hard; the standard metal used for coinage is made up of eleven parts of gold and one of copper. With silver it yields so-called `white alloys,' which are used for jewelry. It combines readily with mercury, forming a white amalgam of a pasty consistency. 'The most ex tensive uses of gold are for coinage, for jewelry, for gilding frames, furniture, books, etc., for electroplating, and in dentistry.