130 ON I'LATINA. 



fine powder, I roasted it with a gentle heat, stirring it con- 

 stantly, to avoid the fumes. 2. I then fused it with an 

 equal quantity of common potash, and thus obtained a 

 metallic button, consisting of platina, silver, lead, copper, 

 and sometimes a little antimony. The iron and part of the 

 lead remained in the scoriae. 3. 1 then separated the copper, 

 antimony, and remainder of the lead, by cupellation; 

 which left me only the silver and platina. 4. I parted 

 the platina from the silver by means of aqua fortis, or the 

 nitric acid of the shops, which dissolved the silver, and left 

 the platina behind. This I washed, and heated again, to 

 give it the metallic lustre. 5. If the lead naturally found 

 in the first metallic button were not sufficient, to carry off" 

 all the copper in the process of cupellation, I subjected 

 the metal to tills operation a second time with a fresh por- 

 tion of lead. 6. On the contrary, if the quantity of silver 

 were too small to allow the aqua fortis to act on the alloy, 

 I added a fresh portion of this metal, as in parting it from 

 gold. 7. I ought to caution the reader, that the aqua fortis, 

 if it be not sufficiently diluted, will dissolve a portion of 

 platina at the same time with the silver ; which is easily 

 perceived by the brown colour the solution assumes. 

 Parting neces- If platina be found in the gray ore of Guadalcanal in 

 the nlaUna' 1 a proportion that will allow it to be extracted with ad- 

 and even tl#e vantage, of which, according to my first researches, there 

 cau scarce be any doubt, it will require to be parted by 

 means of aqua fortis, in the same manner as is practised 

 with respect to the gold extracted from silver ores : and 

 even if there be no advantage to be derived from the pla- 

 tina extracted by this process, it will be necessary to employ 

 it to obtain the silver; for by any other mode these two 

 metals will be found united together from the similarity of 

 their properties. 

 It is in the me- Platina appears to exist in, the metallic state in these ores, 

 for the simple acids do not dissolve the smallest quantity of 

 it, and it is constantly found among the sulphur and silex, 

 when the latter constitutes part of the gangue. It was in- 

 deed by examiuing these residuums of the ores, and treat- 

 ing them in succession with nitric and muriatic acid, that I 

 first perceived the platina. 



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