810 



Upon this plate chips of fir-wood are kindled, then the door, s, which is lined with 

 clay, is closed and luted tight. The fuel is now placed in the vacant space, k, round 

 the upper part of the bell. The fire must be fed-in most gradually, first, with turf, 

 then with charcoal; whenever the bell gets red, the mercury volatilises, and con- 

 denses in globules into the bottom of the basin, B. At the end of 8 hours, should no 

 more drops of mercury be heard to fall into the water, the fire is stopped. When 

 the bell has become cool, it is lifted off; the plates are removed from the candelabrum, 

 d ; and this being taken out, the drawer, a, is slid away from the furnace. The mercury 

 is drained, dried, and sent again into the amalgamation-works. The silver is fused 

 and refined by cupellation. 



From 3 cwts. of amalgam, distilled under, the bell, from 95 to 100 marcs ( Ibs.) of 

 Tellersilber (dish-silver) are procured, containing from 10 to 134 P arts of fine silver 

 out of 16 ; one fifth part of the metal being copper. The teller silver is refined in 

 quantities of 160 or 170 marcs, in black-lead crucibles filled within two inches of 

 their brims, and submitted to brisk ignition. The molten mass exhales some vapours, 

 and throws up a liquid slag, which being skimmed off, the surface is to be strewed 

 over with charcoal-powder, and covered with a lid. The heat having been briskly 

 urged for a short time, the charcoal is then removed along with any fresh slag 

 that may have risen, in order to observe whether the vapours have ceased. If not, 

 fresh charcoal must be again applied, the crucible must bo covered, and the heat in- 

 creased, till fumes are no longer produced, and the surface of the silver becomes 

 tranquil. Finally, the alloy, which contains a little gold, and much copper, being 

 now from 11 to 13 lothig (that is, holding from 11 to 13 parts of fine .silver in 16 

 parts), is cast into iron moulds, in ingots of 60 marcs. The loss of weight by 

 evaporation and skimming of the slag amounts to 2 per cent. ; the loss in silver is 

 inconsiderable. 



The dust from the furnace (Tiegelofeii) is collected in a large condensation chamber 

 of the chimney, and affordg from 40 to 50 marcs of silver per cwt. The slags and old 

 crucibles are ground and sent to the small amalgamation mill. 



The earthy residuum of the amalgamation casks being submitted to a second amal- 

 gamation, affords out of 100 cwts. about 2 Ibs. of coarse silver. This is first fused 

 along with three or four per cent, of a mixture of potash and calcined Quicksals 

 (impure sulphate of soda), and then refined. The supernatant liquor that is drawn 



1799 



1800 



1801 



out of the tanks in which the contents of the casks are allowed to settle, consists 

 chiefly of sulchate of soda, along with some common salt, sulphates of iron and 

 manganese, and a little phosphate, arsenate, and fluoride of sodium. The earthy de- 

 posit contains from to ^nds of 

 a loth of silver per cwt., but no 

 economical method of extracting 

 this small quantity was used. 



Argentiferous or rich lead is 

 treated in Germany by the cupel- 

 lation furnace represented in figs. 

 1799, 1800, 1801, and 1802. 

 These figures exhibit the cupella- 

 tion furnace of the principal smelt- 

 ing work in the Hartz, where the 

 following parts must be distin- 

 guished : (fig. 1801) ], masonry of 

 the foundation ; 2, flues for the escape of moisture ; 3, stone covers of the flues ; 4, 

 bed of hard-rammed scoria; ; o, bricks set on edge, to form the permanent area of 



