258 Remarks on M. Baruel's Process 



fact is, that the chief part of the acrid vapours, was oxide of 

 osmium, which was unnecessarily wasted. 



The note at paragraph 18, has its commentary in the follow- 

 ing observation of M. Vauquelin. " The muriatic acid em- 

 ployed after the nitric, contained likewise a great deal of iron, 

 some copper and palladium, and even platinum and rhodium. 

 This shews that a portion of these last three metals is precipi- 

 tated by the iron in the state of oxide ; otherwise muriatic acid 

 would not have dissolved them. This seems to prove likewise 

 that these metals in precipitating combine with iron and copper, 

 and prevent them from being attacked by nitric acid, even when 

 employed in considerable quantity." The great quantity of 

 oxide of iron which precipitates along with the platinum, palla- 

 dium, and rhodium, is very remarkable." 



The process in § 15 and § 16, is a refinement on the former 

 methods. M. Vauquelin contents himself with the first precipi- 

 tate of platinum by sal-ammoniac, regarding it as quite pure, 

 A great master of chemical analysis, to whom this process of M. 

 Baruel was shewn, remarked, that his aqua-regia contained too 

 much nitric acid ; that if the suitable proportion of muriatic 

 acid be employed, then the platinum may be thrown down pure, 

 at first, by sal-ammoniac ; and that M. Baruel dissolves by his 

 menstruum, a portion of iridium. 



The separation of palladium, under the form of an ammonia- 

 submuriate in § 19, is precisely Vauquelin's method. Of this 

 plan, M. Vauquelin speaks with complacency. " This process, 

 more simple, and more exact than that of WoUaston, depends 

 1. On the insolubility of ammonio-muriate of palladium, even 

 in water slightly acidulous. 2. On the solubility of the muriates 

 of copper and iron in alcohol, and the insolubility of ammonia- 

 muriate of rhodium in the same liquid." Yet the following ex- 

 tract from the same elaborate Memoir, seems to invalidate the 

 above certainty of separation. " Now to obtain the rhodium, I 

 concentrate the liquids from which the palladium has been se- 

 parated, till they crystallize totally on cooling. I put the crystals 

 aside to drain; they dixe frequently of two kinds and of two colours. 

 Some have the form of hexahedral plates, and a fine ruby-red 



