Copper, METALLURGY

OF. Native Copper is found in Cornwall, Brazil, and Siberia, and in enormous deposits on the s. shore of Lake Superior, where ma es have been found of over 400 tons. This ore frequently carries native silver. Red Copper Ore is a sub-oxide of copper of a deep red color, found in Cornwall and Chili. Copper Glance is a shining black mineral, chemically copper sulphide. Copper Pyrites is a bra yellow mineral, sometimes mistaken for gold. It contains copper, iron, and sulphur, and is found in large deposits in Cornwall, Germany, China, Japan and the U. S. The carbonates of copper, Azurite, and Malachite, are important ores, found in large quantities in s. Australia and Chili. In Copper has been known from the earliest times, but the first metal was probably either native metal or else prepared from the oxide or carbonate ores by heating them with carbon. At present all kinds of ores are treated by many different methods, which may be generally cla ed under (1) furnace smelting and (2) aqueous treatment. The first is varied according to whether the ores are combinations with sulphur or oxide ores. treating sulphide ores, the principle is used that copper has greater affinity for sulphur and le for oxygen than most of the other metals it may be a ociated with. The ore is therefore first heated in a furnace with free acce of air, which results in oxidizing some of the foreign metals, such as iron, and driving off some of the sulphur. After this roasting, the ore is melted down in another furnace, when the copper will be found concentrated as copper sulphide with some iron sulphide, a product termed matte, while much iron and foreign matter unite to a slag which floats on top of the matte and can be easily separated from it. A repetition of the roasting and melting gradually removes the impurities and drives off sulphur, until a product containing 90 per cent of copper, called black copper, is obtained. This is roasted until all the sulphur is driven off, which leaves dry copper, containing much oxygen, which is then refined by stirring with a pole of green wood, an operation called poling. These operations are varied in many different ways, one of the principal changes brought into modern practice being the first smelting down of the ore in water-jacketed cupola furnaces instead of on the hearth of reverberatory furnaces. Sulphide ores are frequently first utilized for making sulphuric acid, and the residues then smelted down as above. In Sweden the ore is first roasted in open piles before being put into the furnaces. A recent improvement has been the treatment of the matte in ve els similar to Be emer converters. The molten matte is put into a cylinder lined with fire-brick, and air blown through it, thus oxidizing out its sulphur and leaving in the converter either a richer matte, or even crude copper, if the blowing is kept up long enough. This proce is carried on extensively in Montana. Oxide ores (oxides and carbonates) are either mixed in with sulphide ores or worked by themselves. They are easily reduced alone by mixing with charcoal and smelting down. Wet proce es are applied only to poor ores, whose foreign material is not easily di olved. The principle employed is to get the copper in to the form of a salt in solution, and then separate it from the solution by precipitation with iron or by electric deposition. If the ore is a sulphide, a careful roasting at a moderate heat will produce copper sulphate, which can be washed out. If the ore is an oxide, dilute acids must be used to di olve out the copper. The solutions thus obtained are put into tanks with scrap-iron, which displaces the copper in the solution, precipitating it as a metallic powder, which is washed and melted down. Using electricity, a current is pa ed through the solution, using an iron anode, which di olves as the copper is deposited. These proce es are modified in numerous ways. The crude copper obtained by smelting is frequently refined by electricity. The impure metal is cast into plates, and hung in a solution of copper sulphate, opposite to a thin sheet of pure copper. The current deposits pure copper on the thin sheets, and the heavy plates are correspondingly di olved; the impurities, however, remaining mostly undi olved and falling to the bottom of the tank. Over one-half the pure copper made is thus treated.