Coke

Coke. When coal is heated without access of air, gases are evolved and a residue, coke, remains, consisting chiefly of carbon together with the earthy impurities of the coal. It varies in colour from black to grey, and also in density. It burns with a clear non-sooty flame, giving out great heat. It is therefore very largely used in metallurgical processes. As the coke from gas-works is denser than that required for metallurgical furnaces it is frequently prepared by coking, either simply in piles of lump coal partially covered by small, or in specially constructed kilns or coke ovens. On the Continent it is in general usage as a fuel for ordinary domestic purposes.