The following table, compiled from the sta tistics of the United States Geological Survey, gives the copper production of the United States by decades, and shows the relative amount of the Lake Superior irodnet: Among foreign countries Spain ranks first in the production of copper. Deposits near Huelva, Andalusia. have been worked since Roman times, The ore (pyrites) carries only 2 to 3 per cent. copper, but it occurs in immense deposits and is easily extracted. Chile and Mexico are fin portant copper-producers and give promise of attaining greater prominence in the immediate future.
The great increase in the use of copper in electrical and other industries is shown in the following table, giving, in long tons, the world's production for the decade of 1890-99: Calumet and Hccla is the richest and largest of the Lake Superior mines. While this district has been an active producer for more than fifty years, it still has a promising future, owing to the favorable conditions for deep mining. The most productive copper-mines of Montana are situated near Butte. The deposits, consisting of Copper (symbol, Cu; atomic weight, 03.00) is a red-colo•ed metal with a bright, metallic lus tre. The specific gravity of finely divided cop per is 8.36; that of hammered copper is 8.95. It is very malleable and may be hammered or rolled into thin leaf or drawn into fine wire. Its melting-point is about 1100° C.. and it burns with a green flame. Copper is an excellent con ductor of electricity, and hence its extensive application in the form of wire in electric teleg raphy. copper is used for the manu facture of tubular boilers, for the sheathing of ships, for electrotypes, in coinage, and for nu merous other purposes. It is also much used in the form of alloys with other metals, its princi pal alloys including brass, bronze, hell-metal, speculum-metal, aluminum bronze, and German silver. (See ALLOYS.) Copper combines with oxygen to form four oxides, the quudroxidc or (Cu,01 ; cup•ous oxide, hemioxidc, or protoxidc (Cu,.0) ; cupric oxide, or monoxide lCuO) ; and the peroxide Of these, the more important are the cuprous and cupric ox ides, which form, with acids, series of cuprous and cupric salts. Cuprous oxide is found native as cuprite, or red copper ore. and is used in the production of ruby glass; with the black oxide it forms one of the copper paints used for coat ing the bottoms of ships. Cupric oxide is found native as tcnorite, or black copper ore, and is used to make green and blue glass, and as a pigment. Other important compounds include: Cupric hydroxide, which is used as a blue pig ment by paper-stainers, and when dissolved in ammonia is known as Schiceit.:er's reagent, a
solvent for various forms of cellulose, as cotton, wool, linen, filter-paper, etc.; cuprous chloride. which is used as a pigment under the name of Bromwich: preen; cupric chloride, which finds employment in calico - printing,, in the manu facture of methyl violet and other colors. Cu pric sulphate, or blue vitriol, the most important of the copper salts, may be prepared by dissolv ing metallic copper or its oxides in sulphuric acid; it forms large, transparent, blue crystals which are soluble in water and find extensive employment in calico-printing, in dyeing, in the preparation of pigments, for the preservation of timber, and in agriculture. Another salt, cupric nitrate, is used to some extent in dyeing and calieo-printing, as is also cupric sulphide. Cu pric carbonate, which occurs native as the green malachite and as the blue azurite, two minerals almost identical in their composition, is used as a pigment. An anhydrous basic carbonate, too, is used as a pigment, especially for paper-stain ing,, under the names of Bremen blue, Bremen green, Fcrditer blue, and Ierditer green. Copper oxide, when dissolved in acetic acid, yields the commereial verdigris, which is used in the manu facture of pigments, as an oxidizing agent, in the indigo bath, etc. Many of the copper salts are poisonous, and emetics should be promptly given in eases of poisoning. See ANTIDOTES.
MET.'iLLIMGY. The extraction of copper from its ore consists, first, in the production of crude copper, and, second, in the refining of this crude product. The extraction of crude copper is performed by (I) dry methods; (2) wet methods ; ( 3 ) electro-metallu rgica 1 methods. Copper obtained by the wet or dry methods is called black copper or blister copper, that is, crude copper, and contains a number of foreign substances which interfere with its use in the arts. It must, therefore, be purified or refined, by special processes, which may be either by the dry or electrolytic methods. The most impor tant ores of copper are the sulphuretted com pounds, and next come the oxides, carbonates, and silicates of copper, as well as native copper con taining impurities. All these ores, when sutli ciently rich, are treated by smelting or by the dry method. Wet are employed for ores so poor in copper that they cannot be treated profitably by dry methods; ores containing only one-quarter to one per cent. of can, under favorable eircumstances, be profitably worked by wet methods.