a65 Ketv ]\Tethod of Jeparat'nig Silver 



tion is repeated three and even four times *. This circum- 

 stance will give rife to new and intereliing experiments; but 

 iny obfervations prove in the mean time that maddering, vx 

 general, requires to be managed with the niceft attention. 



XLIV. A neiv Method of feparating Silver alloyed luitb 

 Copper in Bullion. By C. Napione f. 



Mi 



.ETALLURGfSTS well know that argentiferous cop- 

 per, which does not contain half its weight in filver at lead, 

 cannot be fubjefted lo cupellation. In that cafe, recourfe 

 is had to an operation, called liquulion, with lead ; but, un- 

 happily, it is attended with inconvenieaces which in many 

 cafes render it impracticable. 



To exlraft filver from capper completely, in one liquation, 

 practice has (liown in the founderies where this operation 

 is performed on a large fcalc on black copper, that for a 

 quintal of the latter then: mull be at lealt 70 or 80 pounds of 

 copper, and more than 8 or 9 ounces of lilver; and in this 

 cafe the proportion of lead to the copper ought to be 11 parts 

 of the former and 3 of the latter. 



But as in billon (bafe) money the filver generally forms 

 from i-i2th to i-4th of alloy, and fometimes more, it is 

 evident that leveral liquations niull be repeated to inipoverifli 

 the copper; for though in the firft the lead carries with it a 

 great deal of filver, it is not always in the fame proportion, 

 and the latter portions are more difficult to be extracted. 



If we fuppofe that four fucceffive liquations are fufficient 

 to extraft the filver of our billon money, which is of the qua- 

 lity of 3 deniers 10 grains, eftimating it at the lowefl, we 

 fliould have ^^ livres for the whole cxpenfe of the fcparatioii 

 for each quintal of that money. 



If the procefs of the celebrated Cramer, of which M. Jars 

 has ffiven a fliort account in the third volume of his Koyages 

 JSletallurgiques^ can be attended with any advantage, it 

 xvould, however, be of very little ufe to us. 



C. Napione, knowing that fulphur has a greater affinity 

 for copper than for filver, conceived the idea of reducing into 

 £coriae a large qnaulity of rich copper by combining it di- 

 re6tly with lulphur, in the hope of obtaining, by this kind of 

 dry depart, the filver concentrated in a portion of the copper 



' Conce tv t'<l tcetic Iblution of oxide of iron is attended with ntaily 

 t»ie faiTif difficulties. 



+ iroiu tiie Annaies de Cbimie, No. i;2. 



