COPPER.
1. Copper is a ductile and malleable metal, of a pale yellowish red color. It is sometimes found in a native state, but not in great quantities. The copper of commerce is principally extracted from the ores called sulphurets. Copper mines are wrought in many countries; but those of Sweden are said to furnish the purest copper of commerce, although those of the island of Anglesea are said to be the richest.
2. In working sulphureted ore, it is first broken into pieces, and roasted with a moderate heat in a kiln, to free it from sulphur. When the ore is also largely combined with arsenic, a greater degree of heat is necessary. In such a case, it is spread upon a large floor of a reverberatory furnace, and exposed to a greater heat. By this treatment, the sulphur and arsenic are soon driven off.
3. The ore is then transferred to the fusing furnace, and smelted in contact with fuel. The specific gravity of the copper, causes it to sink beneath the scoria into a receptacle at the bottom of the furnace. To render the metal sufficiently pure, it requires repeated fusions, and, even after these, it usually contains a little lead, and a small portion of antimony.
4. Alloys of copper.—Copper is combined by fusion with a great number of metals, and, in such combinations, it is of great importance in the arts. When added in small quantities to gold and silver, it increases their hardness, without materially injuring their color, or diminishing their malleability. An alloy, called white copper, imported from China, and denominated, in that country, pakfong, is composed of copper, zinc, nickel, and iron. It is very tough and malleable, and is easily cast, hammered, and polished. When well manufactured, it is very white, and as little liable to oxydation as silver.
5. Copper, with about one-fourth of its weight of lead, forms pot-metal. Brass is an alloy of copper and zinc. The proportion of the latter metal varies from one-eighth to one-fourth. Mixtures, chiefly of these two metals, are also employed to form a variety of gold-colored alloys, among which are prince's metal, pinchbeck, tombac, and bath-metal.
6. A series of alloys is formed by a combination of tin and copper. They are all more or less brittle, rigid, and sonorous, according to the relative proportions of the two metals; these qualities increasing with the amount of tin. The principal of these alloys are, bronze, employed in the casting of statues; gun-metal, of which pieces of artillery are made; bell-metal, of which bells are made; and speculum-metal, which is used for the mirrors of reflecting telescopes.
7. The alloys of copper were very prevalent among the nations of antiquity, and were used, in many cases where iron would have answered a much better purpose. The instruments of husbandry and of war, as well as those for domestic uses generally, were usually made of bronze, a composition which furnishes the best substitute for iron and steel. The Corinthian brass, so celebrated in antiquity, was a mixture of copper, gold, and silver.
8. The earliest information of the use of this metal by mankind, is found in the fourth chapter of Genesis, in which it is stated, that "Tubal-Cain was the instructer of every artificer in brass and iron." This individual was the seventh generation from Adam, and was born about the year of the world 500.