ELECTRO-METALLURGY

is that branch of Electro-Chemistry which deals with the practical production, refining and working of metals. Many of the metallurgical proce es can be carried out only by the use of electricity. Among these are the manufacture of Calcium Carbide, Aluminum, Sodium hydroxide, metallic sodium, pota ium chlorate, and the refining of Copper. The last is the largest and most important of the electro-chemical industries. Iron and sieel may be produced electrically by pa ing a current through Magnetite (a naturally occurring magnetic oxide of iron, Fe;0.) and carbon, thereby heating the mixture. The Oxygen unites with the carbon and is given off as carbon dioxide. The residue is pure (wrought) iron, cast iron or steel, depending on the proportion of carbon used. It is questionable whether this proce can compete with the Blast Furnace and Be emer Converter in economy; its advantage lies in its simplicity and the fact that the fuel contains no impurities to contaminate the product. Calcium Carbide is produced electro-thermally by the treatment of burnt lime and coke in an arc type of furnace. Aluminum is prepared by the electroylsis of its oxide (A1:0:) di olved in molten Cryolite (3NaF, A1F;). The oxygen unites with the carbon anodes, while the liberated metal falls to the bottom of the cell, whose carbon lining forms the cathode. The electrolytic refining of Copper consists of transferring the metal by the action of an electric current, from an anode of the crude metal to a cathode of the refined metal, using as electrolyte, a mixture of Copper Sulphate and Sulphuric acid. The impurities which contaminate the anode either di olve in the electrolyte, or, remaining undi olved, eventually fall to the bottom of the tank. Copper refined in this manner is 96-98% pure. Silver is similarly refined, using an electrolyte of dilute nitric acid. E (2/4) e (2/4)