Copper is one of the most anciently known metals, deriving its name from Cyprus, large supplies having in Greek and Roman times come from that island. It is a metal of a pale red colour tinged with yellow; chemical symbolCu, atomic weight 63.6. Next to gold, silver, and platinum it is the most ductile and malleable of metals; it is more elastic than any metal except steel, and the most sonorous of all except aluminium. Its conducting power for heat and electricity is inferior only to that of silver. It has a distinct odour and a nauseous metallic taste. It is not affected by water, but tarnishes on exposure to the air, and becomes covered with a green carbonate.
Copper occurs native in branched pieces, dendritic, in thin plates, and rarely in regular crystals, in the primitive and older secondary rocks. Blocks of native copper have sometimes been found weighing many tons. Its ores are numerous and abundant. Of these several contain sulphur and iron or other metal, such as copper glance or vitreous copper (Cua S); gray copper or Fahlerz, one of the most abundant and important ores; and copper pyrites or yellow copper ore (CuFeSg), another abundant ore. The red oxide of copper forms crystals of a fine red colour, and is used for colouring glass.
There are two native carbonates, the blue and the green, the latter being the beautiful mineral malachite, the former also known as blue malachite. Blue vitriol is a sulphate, and is used for dyeing and preparing pigments, as are various other copper compounds. Verdigris is an acetate. The arsenite of copper is the pigment Scheele's green. Schweinfurth green is another copper pigment. All the compounds of copper are poisonous.
Copper is found in most European countries, in Australia and Japan, in Africa and in North and South America (especially in the vicinity of Lake Superior). In Britain the mines of Cornwall have yielded little copper since the end of the 19th century.
Copper is extracted from its ores either by the dry or the wet process. For the former, what is known as the Welsh process is most common in Great Britain. It consists in alternately roasting the ore, and then smelting it in a furnace with a suitable slag, until impure or blister copper is obtained. Before this stage is reached a metallic compound of copper, sulphur, and iron has been produced, technically known as matt, regulus, or coarse metal, and subsequently a tolerably pure sulphide of copper called fine metal. The blister copper is refined by burning off the sulphur, arsenic, and other volatile impurities, and by melting it along with wood charcoal and stirring it with a wooden pole. The quality is then tested, and, if found satisfactory, the copper is cast into ingots.
In extracting the metal from pyrites by the wet process, the ore is first roasted to get rid of the larger proportion of sulphur, then the calcined residue still containing sulphur is mixed with common salt, ground and heated in ovens. The copper is thus converted into chloride, part of which volatilizes, but is condensed, along with arsenic and other substances, by passage through flues and water-condensers. After some hours the calcined mixture is raked out of the ovens, cooled, and transferred to tanks, where it is exhausted by successive treatment with water. The solution, containing chloride of copper, sulphate and chloride of sodium, and iron salts, is next heated along with scrap-iron. Copper precipitates in the form of a ruddy, lustrous, tolerably compact mass, with a crystalline appearance, and mixed with metallic-iron and oxide. The larger pieces of iron are picked out, the precipitate washed and drained, and then rendered compact by heating in a furnace. A slag containing the oxide of iron forms, and the copper, when judged sufficiently pure, is run into moulds.
The crude metal is now usually refined by an electrolytic process, the crude metal serving as anode and a strip of pure copper as cathode. Many alloys of copper, especially those containing tin and zinc, are of much importance, eg, brass, an alloy of copper and zinc; bronze, an alloy of copper with about 8 or 10 per cent of tin; bell-metal, composed of eighty parts of copper and twenty of tin.
Copper is applied to a great many useful purposes. In sheets it is used for the constructing of boilers and stills of a large size, etc; and pipes of various sorts, as well as electircla circuits, wire, lightning-rods, etc., are made of it. It is also used in electrotyping and engraving, for various household utensils and fittings; but its use for household utensils is by no means free from danger on account of the formation of verdigris by the action of acids. Research Copper
Abbreviations
Rocks & Minerals
Research Copper