Page:The American Cyclopædia (1879) Volume X.djvu/264

 258 LEAD about 5 to 6 per cent, of lead and 0*02 of silver. The lead is refined and then enriched by Pat- tinson's process, and cupelled for silver. The silver is dissolved in boiling sulphuric acid and a little gold obtained. The regulus is roasted and smelted with copper ores of class I) and slags rich in lead, producing a second regulus contain- ing 30 per cent, of copper and 0'18 of silver. This operation is thrice repeated, resulting in the production of two enriched reguluses con- taining respectively 54 and 73 per cent, of cop- per. This latter is roasted " sweet " in a re- verberatory furnace, and treated with sulphu- ric acid of specific gravity T5, diluted with its bulk of water, and the oxide of copper dis- solved out, leaving a residue containing lead and silver, and some copper, which is added in the course of the lead smelting. The solution of the copper is crystallized to blue vitriol, and sold as such. In each of the three or more gmeltings of the regulus there are also pro- duced lead, speise, and slag, which are the subject of further treatment. The slags from the ore smelting are treated with ores of the classes and E, in a reverberatory-furnace, producing a regulus (Rohstein) and slag. The former, containing from 7 to 10 per cent, of lead, 4 to 5 of copper, and 0'15 to 0'20 of sil- ver, is added after the roasting to the ore- smelting mixture, as stated above ; while the slag which contains but 1 per cent, of lead and 0-0028 of silver is thrown away. The speise obtained in the various smeltings of ore and regulus is, after concentration of the nickel and cobalt, treated for the extraction of these metals. There is further produced at Freiberg a considerable quantity of ar- senical preparations from the fumes of the furnace, and a small quantity of bismuth is extracted from the test in which the silver is refined. The third of the smelting processes enumerated above, viz., the iron-reduction or precipitation process, finds its best example in the upper Hartz. Here sulphuretted ores are smelted, which contain on an average from 54 to 56 per cent, of lead and O'lO of silver at the Clausthal and Altenau works, and 62 to 64 per cent, of lead and from 0'09 to O'lO of silver at the Lautenthal works ; they con- tain also some copper, zinc, and antimony. They are smelted with the addition of cast iron, in such proportions that the resulting lead shall bear the proportion in weight to the lead regulus of 4 to 3 or 5 to 4. The result of this smelting is practically the same as that at Freiberg ; furnace lead, lead regulus, slag, and occasionally speise, are produced, which are treated substantially in the same way as the corresponding products in Freiberg, The use of cast iron has been in a great measure superseded by that of iron-finery slags, or in the upper Hartz by slags from copper smelting in lower Hartz, which are silicates of pro- toxide of iron containing between 1 and 2 per cent, of copper and a small amount of sil- ver. The reaction in this case depends on the reduction of the iron in the slag and the subsequent action of the metallic iron thus Lead Farnace. Fig. 1. Vertical seetion on line H Y of fig. 2. Fig. 2. Horizontal section on plane V T of fig. 1. A, shaft of the furnace ; .B, chimney ; C, hearth ; D, foun- dation ; E, bottom stone ; a, dam plate ; b, hearth plates of cast iron; c, cast-iron pillars on which the flange d rests ; e, dam ; f, fore heartn ; ^, bridge ; h, tymp stone ; i, breast; fc, slag sprout; I, matte spout; m, syphon tap; P'P 1, P 2 7 &c-i tuyeres; <?, nozzles; r, wind bag&j , main blast pipe ; 2, charging doot.