Copper (Cu) is a highly malleable, ductile, and tenacious red metal greatly used in many industrial arts. It does not resist the action of a rids, and even moisture affects it, causing it to form an oxide known as verdigris; this, under the action of carbonic acid, turns to a green carbonate. Copper is also caused to oxidise by heat; it is volatile only at a great heat. It has a specific gravity of 8"9, and melts at 2,000 F. Commercial copper contains many impurities, amongst them being iron, silver, bismuth, antimony, arsenic, cuprous oxide, lead, tin, and sulphur. Copper is much used in its commercially pure state, but is greatly in demand as the chief ingredient of the important brass and bronze alloys. Copper sometimes occurs native, being then often covered with an oxide and carbonate crust; it is sometimes found in grains in sand, but is more generally obtained by the reductiou of its ores, which are very plentiful. The ores may he reduced - (1) by treating them in reverberatory or blast furnaces, or in both; (2) by the "wet " method; or (3) by the electro - chemical method.

By one German furnace process the ore is oxidised and the sulphur expelled by roasting, and the ore is then smelted in a cupola, two cisterns receiving respectively the slag and metal which flow through tap-holes. Repeated roasting is necessary, and then all sulphates are removed by lixiviation. Silver is removed with lead, which is afterwards separated by cupellation. By another furnace method the copper pyrites is roasted together with chloride of sodium, sulphuric acid being formed; this attacks the soda, and the copper is turned into a soluble sulphate, the iron of the pyrites being then in the form of peroxide. The fumes of the chlorine, set free from the sodium chloride, impregnate lime, and this becomes a bleaching agent. The wet method of reducing copper ore is to grind and roast it, mix it with salt, and again roast it so as to form copper chloride and sodium sulphate, which are then dissolved in dilute acids. Any silver which may be in solution is precipitated by the action of zinc iodide, and the copper chloride solution is siphoned off and precipitated with scrap-iron. After washing the precipitate, it is refined in reverberatory furnaces.

The copper from these may be cast into slabs, and to make these into thin sheets the slabs are anuealed and rolled repeatedly, the rolls being brought nearer at each successive operation; the copper is annealed after each rolling.