COPPEK. 391 COPPER. Tvitli a green ilame. Copper is an excellent con- ductor of electricity, and hence its extensive application in the form of wire in electric teleg- raphy. Metallic copper is used for the manu- facture of tubular boilers, for the slieathiii}; of ships, for electrotypes, in coinage, and for nu- merous other purposes. It is also much used in tlic form of alloys with other metals, its princi- pal alloys including brass, bronze, bell-metal, speculum-metal, aluminum bronze, and German silver. (See Alloy.s.) Copper combines with oxygen to form four oxides, the quadroxidc or sub-oxide (CujO) ; cuprous oxide, hemioxrde, or j>ro1oxide (Cu,0) ; cupric oxide, or monoxide (CuO) ; and the peroxide (CuOi). Of these', the more important are the cuprous and cupric ox- ides, ^^■hich form, with acids, series of cuprous and cupric salts. Cuprous oxide is found native as cuprite, or red coi)per ore, and is used in the production of rubj- glass; ^ith the black oxide it forms one of the copper paints used for coat- ing the bottoms of ships. Cupric oxide is found native as tenorite, 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 tSchwei Iter's reagcul, 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 Bruusn'ick green; 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 dis.solv- ing metallic copper or its oxides in sulphuric acid: it forms large, transparent, blue crystals ^liich 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 calico-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, Verditer blue, and Verditcr green. Copper oxide, when dissolved in acetic acid, yields the conmiereial verdigris, which is used in the manu- facture of pigments, as an oxidizing agent, in the indigo hath, etc. Many of the copper salts are poisonous, and emetics should be promptly given in cases of poisoning. See Antidotes. Metallurgy. The extraction of copper from its ore consists, first, in the production of crude cojjper, and, second, in the refining of this crude product. The extraction of crude copper is performed by (1) dr.y methods; (2) wet methods; (3) electro-metallurgical 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 clectroh'tic methods. The most impor- tant ores of copper are the sulphuretted com- pounds, and next come the oxides, carbonates, and Bilieates of copper, as well as native copper con- taining impurities. All these ores, when suflTi- cicntly rich, are treated by smelting or by the dry method. Wet methods are employed for ores so i^oor in copper that they cannot be treated profitably by dry methods: ores containing only one-quarter to one per cent, of co])per can, under favorable circmnstanees, be profitably worked by wet methods. Dry methods of cop])er-smelting may be classi- fied as follows: Blast-furnace smelting, also known as the (ierman or the Swedish process; rcverberatory smelting, also known as the Eng- lish process : and the converter or Bessemer process, used only in reducing copper mattes. The bla.st-furnace or German process, consists in roasting the ores in special appliances, followed by smelting the roasted material with coke or charcoal in blast-furnaces. The series of cliemical reactions which take place during these opera- tions arc rather too tcclinical to be treated here; the H'sult is co|)per matte, a mixture of copper sub-sulphide and a portion of the original impuri- ties of the ore. This matte is then commonly en- riched by partly calcining it and again smelting it in the blast-furnace ; this second process is not always employed. The matte direct from the original smelting or froin the second enriching process is roasted and then smelted with sili- ceous fluxes in addition to the carbon which is used in the first smelting to produce coarse or black copper. In the rcverberatory process the ore is first partly calcined, and is then smelted in a rcverberatory furnace with a quartz lining, with the addition of siliceous materials or ores if necessary. The resulting matte is then concentrated by being partially roasted and then smelted in rcverberatory furnaces. The matte resulting from the concentrating process is con- verted into crude copper by jiartial roasting fol- lowed by fusion in rcverberatory furnaces. The converting jirocess is not applied to ores, but is usually em])loyed to reduce to coar.se copper the matte produced by either the blast-furnace or the rcverberatory process. It consists in blow- ing a highly subdivided stream of air under pressure through molten matte which is con- tained in a pear-shaped or cylindrical converter lined with quartz ore material. The matte to be blown is first melted in cupolas and from them run into the converter. Xeither the blast- fui-nace nor the reverl:)eratory ])rocess is com- monly used in the pure form, but the two are combined in an attempt to imite the advantages of both. Wet methods of reduction consist in getting into aqueous solution, by means of suitable sol- vents, the cop])cr, which must necessarily occur in some combination suitable for solution and of precipitating it from these solutions by means of suitable precipitants. The copper precipitate thus obtained is refined in the dry way. The ores from which copper is extracted in the wet way contain it in the form of oxide, carbonate, sulphate, and sulphide. From all these ores, except the sulphide, the copper can be dissolved with sufficient rapidity by the aid of a cheap solvent, and as the more energetic solvents are too costly to be applied on a large scale, sulphide ores are transformed into some form suitable for solution by cheai> solvents such as water, hydrochloric acid, sidphuric acid, or solutions of metallic chlorides. To explain the applica- tion and action of the different solvents and pre-
