Handbook of Metallurgy Volume 2; Zinc, cadmium, mercury, bismuth, tin, antimony, arsenic, nickel, cobalt, platinum, aluminium

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1898 Excerpt: ...with an average of 2 per cent. When this is dressed it yields coarse concentrates, tin ore containing from 68 to 72 per cent, of tin, and slimes (schiiche) with from 45 to 48 per cent. These are smelted in conjunction with ores from Bolivia, except when tin of special purity is required, in which case the concentrated ores are smelted by themselves. Ores which contain bismuth are previously roasted and treated with hydrochloric acid for the extraction of that metal. The smelting of these ores is effected in the furnaces described and figured above, which are worked with a dark top and without nose. Slags are added to the charge as a flux. After tapping, the tin is skimmed in the tapping pot and cast into bars. The slag which flows into the forehearth with the tin is from time to time lifted off and thrown into water. If the temperature rises too high, wet charcoal is used. In 24 hours, 22 to 24 cwts. of ore are smelted, using 13 cubic yards of charcoal. The slags contain 10 per cent, of tin. The first smelting (verandern) of the slag, which is previously reduced to the size of peas, follows on the smelting of a run of ore. In this process a higher pressure of blast is used and the diameter of the taphole is increased from 1£ inches to 3 inches. Further, on account of the greater fluidity of the slag from this operation, the tin is Ladled from the forehearth; if it were tapped into the stechherd, the slag would run with it and would stop up the taphole. The slag obtained is quenched in water, crushed and smelted in the same furnace after the slag obtained from ore-smelting is finished. This second smelting of slag is called the treiben. The products are tin and a twice smelted slag which still contains tin mechanically enclosed in it; it is therefore st...