Sodium is made by the Castner process. The materials used are caustic soda and a specially prepared carbide of iron, which is formed by reducing oxide of iron by producer gas, mixing the finely divided iron with pitch, and heating it in closed cylinders. The regenerative furnace contains five egg-shaped retorts each 3 ft. high, and each retort is supported upon a hydraulic lift, by which the retort may be lowered to a cool chamber lor cleaning purposes. When the retort is in position it is forced against the cover, which carries a wide pipe for shooting the charge into the retort; this pipe passes up through the furnace, and is closed while the distillation is proceeding. A lateral pipe passes from the retort to a receiver outside the furnace, partly filled with mineral oil, in which the metallic sodium solidifies as fast as it distils. The plant formerly used consisted of a horizontal cylindrical retort, about 3ft. 6 in. long, connected to the condenser by a straight iron pipe. The materials used are carbonate of soda and finely divided carbon.