28 On the Separation of Tin and Copper from Bell-Metal. 



ablution and other mechanical efforts. The more pondera- 

 ble part of this mass, thus freed from the greatest portion 

 ' of its oxide of tin, was fusible, and a bad kind of cannon- 

 metal consisting of 0*80 of tin and 0*20 of copper. It was 

 far too brittle, on account of its containing too much tin. 

 There was also again a loss in the oxide of tin, which car- 

 ried away with it a portion of copper in the process of ab- 

 lution. 



This process not being satisfactory, I attempted to sepa- 

 rate the portion of tin which was united to the copper ob- 

 tained in the before-mentioned process, by fusing it with a 

 substance capable of effecting a complete fluidity. I sub- 

 stituted for that purpose common glass, and I found that 

 it completely succeeded. Pursuing this method, I became 

 soon sensible that this process was not so ceconomical as I 

 first imagined, for one part of the white metal absolutely 

 required three of glass. The great quantity of glass con- 

 sumed, which was also lost, (for it could only be used 

 once,) was a sufficient reason for giving up this proceed- 

 ing : in short, the process, on account of the great bulk of 

 the mass as well as the real value of the wasted flux, made 

 its prosecution in the large way unadmissible. 



Having found in some other experiments that the oxide 

 of tin obtained by digesting strong nitric acid upon tin was 

 reducible by l-10th of charcoal, I had recourse to the latter. 

 Without detailing all the different processes which proved 

 unsuccessful, I snail merely state that method which suc- 

 ceeds best in the large way, and which is as follows : 



Let the slag from which the metals are to be extracted be 

 ground to powder; mix it with 0*08 of charcoal powder, 

 and fuse the mixture in a reverberatory furnace for six 

 hours; after which remove the fused metal in the usual 

 maimer. The glass which covers the reduced metal is to 

 be put aside for further reduction ; for it is capable of yield- 

 ing a metal of (V75 of tin and 0*25 of copper. 



The metal thus obtained by means of charcoal always 

 consists of from 45 to 50 of copper and an equal quantity 

 of tin. To diminish its quantity of tin it must again be 

 fused in a reverberatory furnace capable of exposing a large 

 surface of the fused metal to the contact of air : by this 

 means its surface soon becomes covered with a crust, con- 

 sisting of oxide of tin and oxide of copper. By thus keep- 

 ing the metal melted for some time it soon becomes con- 

 verted into bell-metal, and when this is accomplished it 

 must be drawn from the furnace. 



The gray oxide which is during this process obtained, 



when 



