coal tar
coal tar
coal tar
coal′ tar`
n.
coal tar
| Noun | 1. |  coal tar - a tar formed from distillation of bituminous coal; coal tar can be further distilled to give various aromatic compounds |
| 单词 | coal tar | |||
| 释义 | coal tarcoal tarcoal tarcoal′ tar`n. coal tar
coal tarcoal tar,product of the destructive distillation of bituminous coal. Coal tar can be distilled into many fractions to yield a number of useful organic products, including benzene, toluene, xylene, naphthalene, anthracene, and phenanthrene. These substances, called the coal-tar crudes, form the starting point for the synthesis of numerous products—notably dyes, drugs, explosives, flavorings, perfumes, preservatives, synthetic resins, and paints and stains. The residual pitch left from the fractional distillation is used for paving, roofing, waterproofing, and insulation.Coal Tarone of the products of coal coking; a viscous black liquid with a characteristic phenol odor, a density of 1, 120–, 250 kg per cu m, and a yield of ~ 3 percent of the coal bulk after coking. Coal tar was originally (in the first half of the 19th century) a waste product of gas production. Numerous aromatic hydrocarbons and their derivatives were later discovered in coal tar and have been used since the second half of the 19th century as raw material in the synthesis of dyes, medicines, and other products. Coal tar is a complex mixture of heterocyclic aromatic compounds and their derivatives. These compounds boil off over a broad range of temperatures (see Table 1). The composition of coal tar from different plants is uniform, depending less on the coal composition than on the coking conditions. More than 400 individual compounds have been extracted from coal tar, and some of them are produced on an industrial scale. The primary processing of coal tar is carried out at coke by-product plants. The tar is distilled in units that include a tube furnace for heating and evaporation and rectifying columns for separating the distillate into fractions. The individual substances are extracted from the coal tar fractions (see Table 1) either by crystallization or by treatment with reagents (for example, an alkali solution in the extraction of phenols). Among the residues left after extraction are process oils, which are used as the absorbers of benzene products from coking gas, for preserving wood, and in producing lamp black. Pitch (the residue after separating the coal tar into fractions) is used for manufacturing electrode coke and coatings. Coal tar production in the USSR has been growing steadily; the USSR has the highest output and the most complete processing of coal tar in the world. REFERENCESKoliandr, L. Ia. Ulavlivanie ipererabotka khimicheskikh produktov kok sovaniia, 2nd ed. Kharkov, 1962.Litvinenko, M. S., and I. M. Nosalevich. Khimicheskie produkty kok >sovaniia dlia proizvodstva polimernykh materialov. Kharkov, 1962. D. D. ZYKOV coal tar[′kōl ‚tär]coal tarcoal tartar[tahr]coal tar(kōl tar),coal tarCons Unpleasant odour, carcinogenic Coal tar is usually combined with UVB light coal tarTherapeutics A blackish, semisolid byproduct of the destructive distillation of bituminous coal, which contains benzene, naphthalene, phenols, and other organic compounds; CT is used to treat psoriasis, and may induce clearance of psoriatic plaques Cons Unpleasant odor, carcinogenic; CT is usually combined with UVB light. See Psoriasis.coal tarA complex mixture of organic substances, especially polycyclic hydrocarbons, derived from the distillation of coal. Although the action of this mixture is not well understood, coal tar preparations are used empirically to treat various skin disorders such as ECZEMA and PSORIASIS. The drug is on the WHO official list. It is contained in numerous trade preparations such as Baltar, Capasal, Carbo-Dome, Gelcotar, Pentrax, Polytar, Psoriderm and Tar Band.coal tar
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