COPPER AND ITS MANUFACTURES. Copper is one of the metals with which the Greeks were acquainted ; it was used by them, alloyed with tin, for cutting and warlike in struments, before iron was known, or at any rate before it was common.
Copper has a red colour, and is capable of receiving a good polish ; when warmed or rubbed, it emits a disagreeable smell, and it imparts a nauseous taste : all its preparations are poisonous. It is both malleable and duc tile, and is so tenacious, that a wire TZ-S-0. of an inch in diameter supports a weight of 302 pounds without breaking ; it is extremely sonorous, and is a good conductor of heat and electricity. It melts at a temperature about 1196° Fahr.
This metal is one of those which occur in the greatest number of places and in the largest quantity. It is found in small propor tion in a metallic state, both crystallised and non-crystallised. Its ores are very numerous, the chief being sulphuret of copper and iron (Copper Pyrites), and sulphuret of copper (Nitreous Copper Ore). It occurs also na turally in some oxides and salts.
Copper pyrites occurs in the north of Europe, in England, especiallyin Cornwall, Devonshire, and Anglesey, and in many parts of Asia and Africa, and the American continents.
In 1844, a vein of very productive copper ore was discovered in South Australia. In 1846 the owners of the Capunda mine shipped to England 1200 tons of copper-ore, which sold for 251. a ton, while English copper ore brought only 191. But the Bnrra-Durra mine is perhaps the richest in the world. It con tains a layer 17 feet high and very wide, which is worked like a quarry. The ore is a pure oxide of copper, and fit to be put at once into the smelting forge, and yielded in 1846 from 35 to 75 per cent. of pure metal. In July 1846, several tons of ore from this mine were sold at Swansea for 311. lls. a ton ; and during the six months preceding May 1847, 2700 tons were raised from the same mine, which yielded 87 per cent. of pure copper, and sold for 311. a ton. The shares in this mining company, on which only Si. have been paid, now command a price of more than 2001. ; and even at that price they yield a very large dividend. Such is the facility of working the Burra-Burra mine, that in 30 days 8 miners dug out 80 tons of ore. The copper ore ex ported from South Australia in six years was as follows :— There seems to be remarkable evidence of the existence of large masses of native copper around the shores of Lake Superior. One such piece was met with a few years ago, at Outanagon, which weighed two tons ; but a Toronto newspaper, in 1846, gave an account of a mass of copper, far exceeding in bulk any piece of native metal, probably, yet seen in the world. The miners had excavated 90 feet
horizontally without coming to the end of its length they had sunk 4 feet without finding the limit of its depth; but the thickness was about 11 feet. The part exposed to view was estimated to weigh 80 tons, and to be worth 25,000 dollars. It was stated that machinery was about to be erected for sawing the block into moderate pieces, as the only mode of re moving it from its bed. Since that time fur ther indications of the richness of this store have been obtained ; but the country is so scantily supplied with roads, that some time will elapse before mining operations can be regularly carried on.
The copper of England is chiefly produced from copper pyrites, yielded by the mines of Cornwall and Devonshire. As coal is scarce in those counties and plentiful in South Wales, the ore is conveyed to the latter district for smelting.
The first process in smelting copper is to calcine the ore ; this is done by heating it in a calcining oven, which expels the arsenic and the sulphur contained in the ore, oxidises the copper and the iron, and reduces them to a black powdery state. This powder is then melted in a highly heated oven ; and when liquid the mass is well stirred, to allow the metallic sulphuret to separate from the earthy matter. This metallic sulphuret is drawn off into a vessel of water and granulates into coarse metal, which is, weight for weight, four times as rich in copper as the original ore. The coarse metal is again calcined, and again melted ; if drawn off into water, it obtains the name office metal, but if into sand, blue metal : it now contains 60 per cent. of copper (the coarse metal having about 33 per cent.). Another calcination and another melting bring it to the state of coarse copper, which contains 80 to 90 per cent. of pure copper. This coarse copper is exposed to a high heat in a roasting furnace, by which volatile matters are expelled, and the metals become oxidised ; it is kept in a melted state for many hours, and is drawn forth from the furnace as blistered copper, almost wholly free from sulphur, iron, and other impurities. The blistered copper is transferred to a refining furnace, covered with charcoal, and is brought to a liquid state. It is thus rendered tough and malleable, and fit for subsequent manufacturing processes.