LEAD 71 



ferous lead contained 0-75 per cent, of zinc; but after it had been subjected to the 

 action of steam, it yielded only the most feeble traces of zinc. 



A process for the desilverisation of lead by zinc has been described by E. Koch in 

 the Berg- und Huetten^naennischc Zeitung. In order to make the process continuous 

 the author liquates his lead from copper in a reverberatory furnace -with an in- 

 clined hearth. The liquated lead is received in a Pattinson kettle, -which when it 

 contains a charge is emptied by a siphon-tap into a lower kettle. In the second 

 kettle the antimony is oxidised by steam, and the lead then siphoned into the lower 

 kettles, where it is desilverised by zinc, the latter being fastened in front of the lower 

 mouth of the siphons, so as to bring it into intimate contact with the lead. The 

 desilverised lead is then siphoned into a still lower kettle, where the zinc is removed 

 by steam, and then siphoned into a still lower kettle, whence it is siphoned into irou 

 moulds. The advantages claimed for this method of plant are, a more perfect utilisa- 

 tion of heat, greater production of metals before the addition of zinc (i.e., copper and 

 antimony), saving in the amount of zinc, less wear of kettles, and a more suitable 

 shape of these last. f 



Decopperisation of Lead by Zinc. Mr. W. Baker of Sheffield has successfully 

 carried out this process. When a certain portion of zinc is melted with lead contain- 

 ing copper, a zinc alloy with a small portion of lead is formed, and most of the copper 

 is withdrawn from the lead with it, which floata on the surface in a pasty mass, and 

 may be skimmed off. 



In operating upon 100 tons of lead containing from 10 to 15 oz. of copper to the 

 ton, the copper was reduced on the average to 1 oz. and 21 grs. per ton. 



Mr. Baker thus describes the operation : Five tons of lead are melted, skimmed, and 

 kept sufficiently hot to prevent the metal setting at the sides of the pot. 28 Ibs. of 

 zinc are melted with about 2 cwts. of lead in a small pot adjacent. This pot already 

 contains about 14 Ibs. of zinc, together with some lead from a previous operation. 

 When quite liquid more lead is added from the larger pot, in order to dilute the alloy 

 before mixing with the entire charge. The contents of the small pot, which should 

 be not enough to prevent any alloy separating, are then added to the charge and 

 stirred well into the molted metal. The fire is now withdrawn, and the whole allowed 

 to cool down. In a short time a pasty alloy rises to the surface and is removed by a 

 perforated skimmer into the small pot. This operation is continued until the lead 

 begins to set at the sides of the pan. The charge must then be re-heated, and the 

 alloy in the small pot liquated by heating at a regulated temperature, which will 

 permit of the zinc alloy being removed from a quantity of zinciferous lead, which will 

 be left with only a trace of copper. 14 Ibs. more zinc are now melted with this 

 residue in the small pot, and the operation is repeated. More certain results are 

 obtained by thus adding the zinc in two portions. Finally, all the zinc dross and 

 alloy are liquated in the small pot. The quantity of alloy obtained is about 1 cwt. 

 This will contain about 25 per cent, of zinc, or 28 Ibs. of the zinc employed for one 

 operation. It may be estimated that 14 Ibs. will be left in the decopperised lead, and 

 14 Ibs. also in the liquated product remaining in the small pot ready for the next 

 operation. The zinc remaining in the decopperised lead is oxidised in a reverberatory 

 furnace with a slag bottom, or in a pan such as is used in the furnaces for softening 

 hard lead. In a round pan containing from 8 to 10 tons, set in a furnace of the latter 

 description, a charge was worked off in about 30 hours, including charging and tap- 

 ping out. From 90 tons an average of 95 per cent, of softened lead was obtained. 

 The dross was easily reduced, and yielded ordinary soft lead. 



The zinc alloy containing copper and also most of the silver is best economised 

 by melting down in a small blast-furnace, when a rich argentiferous lead may bo 

 obtained. 



Natro-Metallurgy. The various processes of refining lead employed at the present 

 day causes, in cases where the metal is impure, considerable waste, and necessitate the 

 reduction of an enormous quantity of oxide, to which they are, besides, inadequate for 

 the removal of certain foreign metals. A new plan, which has recently been devised 

 by MM. Pagen and Ecus of Marseilles, France, allows the complete refining of any 

 argentiferous lead without the formation of oxides of lead, and has, according to the 

 Chronique de I' Industrie, the particular advantage of permitting the collection of all 

 foreign metals, of which the value maybe worth considering. The process is founded 

 on the property which a bath of caustic, hydrated, melted alkali possesses in dissolv- 

 ing, or at least oxidising, successively, all the metals except three, by drawing them 

 into a soluble scoria, in a state of igneous fusion. The three exceptions are lead, 

 silver, and gold. The metals united with the lead are, one after the other, removed 

 by melted soda, the action of the bath being maintained, first by a jet of steam, 

 designed to restore constantly the water of the hydrate from which the metals gain 

 oxygen, and urged according as the metals are in a less degree oxidisable, either by a 



