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a product of the destructive distillation or carbonization of wood. A distinction is made between the residual tar remaining from the aqueous distillate after heat treatment of wood, the soluble wood tar found in solution in this distillate, and the extracted wood tar obtained by extraction from the aqueous distillate. Residual wood tar is a viscous, oily liquid of dark brown to black color, with a pungent odor and a density of 1,000 to 1,150 kg per cu m. It is a complex mixture of organic substances: phenols (10 to 25 percent), acids (10 to 30 percent) and neutral substances (40 to 55 percent). The phenols include phenol proper, cresols, xylenols, o-ethyl-phenol, pseudocuminols, pyrocatechin, guaiacol, and methyl ether of pyrogallol. The acids are represented by the fatty series from formic to capryl, including palmitin, arachidic, and behenic, as well as the unsaturated acids of this series and the resin acids (abietic and others). Among the neutral compounds are ketones, aldehydes, alcohols, and hydrocarbons of various classes. During distillation of residual tar, various oil fractions are obtained (55 to 60 percent), as well as pitch with melting temperatures of 70° to SOT (40 to 45 percent). The middle fraction of the oils (240° to 310°C) is used as an inhibitor in fuels and oils. Other oils obtained are froth flotation agents, softeners for the rubber industry, and other valuable products. Core binders are obtained from the pitch. In addition, residual tar is used as a wood preservative. Soluble wood tar contains phenols, carbohydrates, and lactones and is used to obtain reducers of viscosity in clayey solutions and core binders. Extracted tar, containing 30 percent and more phenols, is also used to obtain viscosity reducers.
REFERENCESKozlov, V. N., and A. A. Nimvitskii. Tekhnologiia pirogeneticheskoi pererabotki drevesiny. Moscow-Leningrad, 1954.
Sumarokov, V. P. Khimiia i tekhnologiia pererabotki drevesnykh smol. Moscow-Leningrad, 1953.
Sloevye melody energokhimicheskogo ispol’zovaniia topliva. Moscow-Leningrad, 1962.