Copper is a malleable,ductile metal.It is the best conductor of electricity known,except silver.Copper is not affected by dry air but slowly attacked under ordinary atmospheric conditions,forming a coating of a green basic carbonate.This coating abheres to the copper and protects it from further action. Copper in the form of wire,bars,etc.,is the most commonly used conductor of electricity.Because of its resistance to corrosion ,metal roofing for buildings and coveringsforships' bottoms are made of it. Two widely used alloys of this metal are brass,an alloy of copper and zinc,and bronze,an alloy of copper and tin.Phosphor bronze contains in addition to these metals one to for per cent of phosphorus,which is present as the phosphide of one of the metals.It is a hard alloy,not easily corroded,and is used for making such things as ships' propellers and shafting.
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