DISTILLATION OF COAL

When coal is heated to a high temperature in retorts, out of contact with air, a number of volatile products are distilled off, a residue of coke being left in the retorts. The principal volatile products are illuminating gas, coal tar and ammoniacal liquor. The tar and the liquor, which leave the retorts in the form of vapor, are condensed by cooling, and are thus separated from the gas, which consists of a mixture of illuminants, diluents, and impurities. The illuminants consist of ethylene, propylene, butylene, acetylene, allylene and benzine. The diluents are hydrogen methane and carbon monoxide, and the chief impurities nitrogen, carbon dioxide and sulphuretted hydrogen. See Coat Tar Propucts.