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COPPER —(L. cuprum, from the island of Cyprus), Cu; atomic weight 63.546; atomic number 29; melting point 1083.4 ± 0.2°C; b.p. 2567°C; specific gravity 8.96 (20°C); valence 1 or 2. The discovery of copper dates from prehistoric times; it is said to have been mined for more than 5,000 years. It is one of man's most important metals.

Copper is reddish colored, takes on a bright metallic luster and is malleable, ductile and a good conductor of heat and electricity (second only to silver in electrical conductivity). The electrical industry is one of the greatest users of copper.

Copper occasionally occurs native, and is found in many minerals such as cuprite, malachite, azurite, chalcopyrite, and bornite. Large copper ore deposits are found in the U.S., Chile, Zambia, Zaire, Peru, and Canada.

The most important copper ores are the sulfides, oxides, and carbonates. From these, copper is obtained by smelting, leaching, and by electrolysis. Its alloys, brass and bronze, long used, are still very important; all American coins are now copper alloys; monel and gun metals also contain copper. The most important compounds are oxide and sulfate, blue vitriol; the latter has wide use as an agricultural poison and as an algicide in water purification. Copper compounds such as Fehling's solution are widely used in analytical chemistry in tests for sugar. High-purity copper (99.999 + %) is available commercially.

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