Alloy

a mixture of two or more metals brought about by melting them together. Copper is modified for special purposes by alloying it with other metals. The amount of other metals combined with copper in some of the common alloys may be stated as follows: Brass contains 30 to 40 per cent of zinc; bronze, 4 to 10 per cent of tin, 2 or more of zinc, and usually some lead; gun-metal, 9 per cent, and bell-metal, 25 per cent of tin; German silver, 20 to 40 per cent of zinc and 10 to 20 per cent of nickel. Among alloys not containing copper, soft solder contains 50 per cent each of tin and lead; pewter, 80 per cent of tin and 20 per cent of lead; type metal, 70 per cent of lead, 20 per cent of antimony, and 10 per cent of tin. The nickel alloy used in coining contains 75 per cent of copper and 25 per cent of nickel. Alloys in which mercury forms one of the components are known as amalgams. Of the common metals, iron is the least miscible with mercury. The principal coins of the United States are alloys of gold and silver with copper. In alloys of the noble metals, the degree of fineness is indicated by "carats." Pure gold is 24 carats fine. Gold 22 carats fine, means 22 parts of gold to 2 parts of some other metal. American, French, and German coins are 21.6 carat, or 90 per cent gold.