The carbonaceous residue of the destructive distillation (carbonization) of bituminous coal, petroleum, and coal tar pitch. The principal type is that produced by heating bituminous coal in chemical recovery or beehive coke ovens (metallurgical coke), one ton of coal yielding approximately 0.7 ton of coke. It is used chiefly for reduction of iron ore in blast furnaces and as a source of synthesis gas. Petroleum yields coke during the cracking process. Coke from petroleum residues and coal tar pitch is used for refractory furnace linings in the electrorefining of aluminum and other high-temperature service and for electrodes in electrolytic reduction of Al2O3 to aluminum, as well as in electrothermal production of phosphorus, silicon carbide, and calcium carbide.