1190 



ZINC 



to that obtained from the nozzles, whilst the pure metal is cast into ingots, weighing 

 about 28 Ibs. each. At the expiration of twelve hours from the time of charging, the zinc 

 is again tapped, and the residue remaining in the retorts withdrawn. The retorts are 

 immediately recharged, and the operation of reduction is conducted as above described. 



The residues obtained from the retorts, after the first working, are passed through 

 a crushing-mill, mixed with a further quantity of small coal, and again treated for the 

 metal they contain. The earthen adapters or cones, when unfit for further service, 

 are crushed and treated as zinc ores. 



In order to work these furnaces with economy, it is of the greatest importance that 

 they should be constantly supplied with a full number of retorts, since the amount of 

 fuel consumed, and the general expenses incurred for each furnace, will be the same if 

 the apparatus has its full complements of retorts, or if one half of them are broken 

 and consequently disabled. 



It is therefore necessary, in all zinc-smelting establishments, to keep a large stock 

 of well-seasoned retorts, which, before being introduced into the furnace, to make good 

 any deficiency caused by breakage, are heated to full redness in a kiln provided for 

 that purpose. The Belgian process of zinc smelting is that which is at present most 

 employed in this country. The principal localities in which ziuc ores are treated are 

 Swansea, Wigan, Llanelly, and Wrexham. 



2155 



SUesian Process. In the zinc works of Silesia the furnaces employed differ con- 

 siderably from those used in the Belgian process. 



Fig. 2153, represents an elevation, and fig. 2154, a vertical section of the Silesian 

 furnace. The distillation is effected in a sort of muffle of baked clay, M, 'figs. 2155 

 and 2156 ; these are each about 3 feet 3 inches in 

 length, and 20 inches in height. The front of this 

 muffle is pierced with two apertures. The lower open- 

 ing, d, serves to remove the residues remaining in the 

 retorts after each operation, and is closed during the 

 process of distillation by a small door of baked clay, 

 firmly luted in its place. In the upper opening is 

 introduced a hollow clay arm, bent at right angles, 



a, b, c, and which remains open at c. An opening at 



b, permits of charging the retort by means of a proper 

 scoop, and this, during the operation, is closed by a 

 luted clay-plug. From six to ten of these muffles or 

 retorts are arranged in rows, on either side of a fur- 

 nace provided with suitable apertures for their intro- 

 duction. They are securely luted in their places, and the openings closed by sheet- 



2156 



