Manganese, METALLURGY

OF. On smelting iron ores containing manganese minerals, in the blast furnace, the pig-iron produced contains manganese. When the proportion of manganese reaches 10 to 20 per cent, the iron breaks with large, flat, lustrous planes, and is called spiegeleisen. This is used in steel making, to introduce carbon and manganese into steel. Iron with 80 to 85 per cent of manganese has been made in blast furnaces, and is called ferro-manganese. It is used in making the soft varieties of steel. To obtain pure manganese, two methods are used. The chemical method, of Greene and Wahl, consists in di olving pure manganese oxide in melted cryolite, and then adding metallic aluminium, which at once oxidizes, and sets free pure manganese. The operation is conducted in graphite crucibles lined with magnesite, and the manganese produced is nearly chemically pure, being particularly free from iron and carbon. The electrolytic method was used first by Bunsen, 1854, who electrolyzed an aqueous solution of manganese chloride by a very strong current. This method is very slow and expensive; a better way is to electrolyze a melted bath of cryolite in which manganese oxide has been di olved, the manganese separating out as a crystalline powder. Besides its use in ordinary steel, Had field has described a manganese steel, containing 14 to 20 per cent of manganese, which is extremely hard and tough. Manganese bronze is an alloy of copper and manganese. Aluminium is hardened and strengthened by a small percentage of manganese.