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calcium carbide[′kal·sē·əm ′kär‚bīd]
CaC2 a compound of calcium and carbon; one of the most important carbides used in technology. Chemically pure calcium carbide is colorless; industrial calcium carbide varies in color from light brown to black. Calcium carbide has a density of 2.2 g/cm3, and a melting point of 2300°C. Calcium carbide interacts with water to form acetylene: CaC2+ 2H2O = C2H2 + Ca(OH)2; the process is carried out in an excess of water for withdrawal of the liberated heat (30.4 kcal/mole, that is, 127.3 kilojoules per mole). Upon heating, calcium carbide interacts with nitrogen to form calcium cyana-mide: CaC2 + N 2 = CaCN2 + C.
Calcium carbide is prepared in electric furnaces at temperatures ranging from 1900° to 1950°C according to the reaction CaO + 3C = CaC2 + CO, in which a large quantity of heat (450.5 kilojoules per mole) is absorbed. Lime and anthracite or coke serve as raw material for the process. Most of the operating carbide furnaces have an opening at the top; CO is burned down to CO2 after its discharge from the furnace. Closed furnaces with CO extraction have also been constructed. Calcium carbide has found wide application in technology, primarily in the manufacture of acetylene and calcium cynamide and in the reduction of alkali metals.
REFERENCESKuznetsov, L. A. Proizvodstvo karbida kaVtsiia. Moscow-Leningrad, 1950.
Strizhevskii, I. I., S. G. Guzov, and V. A. koval’skii. Atsetilenovye stantsii, 2nd ed. Moscow, 1959.