Online Encyclopedia


Online Encyclopedia
Originally appearing in Volume V05, Page 304 of the 1911 Encyclopedia Britannica.
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M3C = manganese, iron ; M2C = molybdenum ; M3C2= chromium ; MC = zirconium ; M4C3 = beryllium, aluminium ; M2C3 = uranium; MC2 = barium, calcium, strontium, lithium, thorium, &c.; M C4 = chromium. The principal methods for the preparation of carbides may be classified as follows:—(1) direct union at a high temperature, e.g. lithium, iron, chromium, tungsten, &c.; (2) by the reduction of oxides with carbon at high temperatures, e.g. calcium, barium, strontium, manganese, chromium, &c.; (3) by the reduction of carbonates with magnesium in the presence of carbon, e.g. calcium, lithium; (4) by the action of metals on acetylene or metallic derivatives of acetylene, e.g., sodium, potassium. The metallic carbides are crystalline solids, the greater number being decomposed by water into a metallic hydrate and a hydro-carbon; sometimes hydrogen is also evolved. Calcium carbide owes its industrial importance to its decomposition into acetylene; lithium carbide behaves similarly. Methane is yielded by aluminium and beryllium carbides, and, mixed with hydrogen, by manganese carbide. The important carbides are mentioned in the separate articles on the various metals. The commercial aspect of calcium carbide is treated in the article ACETYLENE.
End of Article: M3C

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