CUPRUM - COPPER, Cu, = 63.4.

This metal (which has its name from Cyprus) is now obtained chiefly from the mines of Cornwall, of the Pyrenees, and of Fahlun in Sweden, in the form of a double sulphide with iron (copper pyrites, Cu2Fe2S3): an oxide, a sub- or red oxide (cuprite), and an oxycarbonate (malachite), also occur, as well as arseniates, phosphates, etc.

The metal is extracted from the ores by a process of roasting and fusion; a purer form by electrolytic decomposition of the pure sulphate.

Brass is a compound of copper with zinc (but often contains some lead), and bronze is an alloy of copper, tin, and zinc: ordinary commercial copper may contain arsenic.

Characters And Tests

Copper is the only red metal; it is lustrous, malleable, and ductile, of sp. gr. 8.92; unaltered in dry and cool air, in moist air it becomes coated with hydrated carbonate, and at a red heat is oxidized. In contact with acids, alkalies, or fats, it is readily acted on, with formation of various green compounds, acetates, or oxides, commonly known as verdigris. It is soluble in nitric acid, in sulphuric acid with heat, and in hydrochloric acid if air be present, also in ammonia. It forms cuprous and cupric salts.

Tests may be remembered by their color, as (1) the red test, shown by immersing clean iron in an acid solution of copper, when the red metal will be deposited; (2) the blue test, shown by the coloration produced with excess of ammonia; (3) the brown test, by the bulky reddish-brown precipitate which occurs with ferrocyanide of potassium (R. W. Smith).