Coal tar is a thick, black, sticky liquid obtained as a by-product in the manufacture of coke and coke oven gas from soft coal. Various grades of tar are recovered by condensing (changing to liquid) hot vapors from a coke oven or a coal gas producer. Manufacturers heat coal tar and condense its vapors to produce light oils, such as benzene and toluene. Benzene is used as a solvent and in the production of perfumes and some gasolines, and toluene is used in the manufacture of dyes, paints, explosives, and antiseptics.
Tar acids, such as carbolic acid, and tar bases, such as aniline, are other coal tar products. Carbolic acid and aniline are used to make dyes. Creosote and pitch are heavy liquid coal tar products. Creosote preserves wood, and pitch is used in the manufacture of roofing materials and paint. Sir William H. Perkin, an English chemist, pioneered in coal tar chemistry by making mauve, the first synthetic dye. Petrochemicals (chemicals made from petroleum) are increasingly supplementing coal tar chemicals for use in industry and chemistry.
