and water) which constitute about 40 per cent of the weight of the coal. The residual product, the coke, is a light, porous mass with a considerably higher percentage of fixed carbon than bituminous coal. In regard to composition, coking accomplishes artificially somewhat the same result reached by nature in its slow development of high-grade coals, but the texture of coke is far different from that of coal. Not all bituminous coals are suitable for coke manufacture; and such coals are frequently divided into two classes, known as coking and non-coking coals. Coke is used principally for smelting purposes. Because of its spongy, porous texture, it burns more rapidly and intensely than coal.
The gases eliminated in coking are wasted in the old-fashioned "beehive" ovens, but in modern "by-product"