for procuring pure Platinum. 



quantity of palladium, for I have in vain endeavoured, in the 

 above experiment on crude platina, to obtain a larger quantity 

 of palladium than I have stated, by using more of the prussiate 

 of mercury, or to procure any precipitate by the same means 

 from a solution of pure platina. The prussiate of mercury is 

 consequently a test by which the presence of palladium may be 

 detected in any of its solutions*." 



In paragraph 22, M. Baruel directs to saturate the potash, 

 in the alkaline compound of oxide of osmium, with nitric acid, 

 and then to distil ; but as the slightest excess of this acid would, 

 cause it to come over with the volatile oxide in the subsequent 

 distillation, it seems preferable to employ sulphuric acid, as 

 enjoined by Mr. Tennant. This excellent chemist also suggested 

 the collection of the oxide that rises during the solution of the 

 iridium ore. " As a certain quantity," he says, *' of this oxide 

 is extricated during the solution of the iridium in marine acid, 

 that part may also be obtained by distillationf ." M. Thenard 

 does not seem to have been aware of this fact, since he lately 

 ascribes to M. Laugier the merit of the same suggestion. " II 

 a reconnu que, dans le traitement de la mine de platine par I'acide 

 nitro-muriatique, une partie d'osmium etait attaquee, et que 

 cette partie se vaporisait avec une certaine quantite d'acidej." 



It is hardly necessary to allude to the coarse method of the 

 Marquis Ridolfi, described in the first volume of ihis Journal, 

 page 259. To fuse crude platinum with half its weight of lead, 

 to reduce the alloy to powder, to mix it with sulphur, to expose 

 it to a strong heat in a covered crucible ; to re-melt, with a little 

 lead, the brittle button first obtained, and to hammer it at a 

 white heat, upon a hot anvil, to extrude the lead, are directions 

 nearly impracticable ; and useless if they could be practised ; 

 for the foreign metals cannot be thus separated from the pla- 

 tinum. 



The practice in Paris of alloying the pulverulent pure plati- 

 num with one eighth of its weight of arsenic ; and of exposing 

 the ingot of alloy to an open heat, progressively raised to white- 



♦ Phil. Tran. 1805, page :12(J. f P'"'- Tran. 1804, page 416. 



} Traits de Chime, vol. ii, page 6yO, first eilitiou. 



