36 Memoir upon Palladium and Rhodium. 



niac from its nitro-muriatic solution, I put into the mother- 

 waters and the washings, united together, pieces of iron, in order 

 to precipitate the various metals which accompany the platina 

 in its ore. 



I treated the black precipitate which resulted from it by the 

 nitric and muriatic acids, employed in succession cold. When 

 these two acids ce.ised to act, I washetl the residue and dried it. 

 During this operation there were emitted various very acrid 

 white vapoius, which I ascertained, upon heating a portion of 

 this residue in a retort, to be sub-muriate of mercury mixed 

 unth muriate of copper: the subUmate also contained globules 

 of mercury, and a black substance Avhich I took for osmium 

 from its smell. 



The nitric acid Vvhich had been used in washing the precipi- 

 tate just mentioned, contained abundance of iron, copper, and 

 a small quantity of palladium, although the operation had been 

 performed in the cold way. 



The muriatic acid employed after the nitric acid still con- 

 tained abundance of iron, copper, palladium, and even platina 

 and rhodium. This proves that a part of these three last me- 

 tals is precipitated in the state of oxide by the iron, otherwise 

 the muriatic acid would not have dissolved them : it seems to 

 prove also that these metals in being precipitated combine Avith 

 the iron and the copper, and prevent them from being attacked 

 by the nitric acid even when employed in large quantities. 



I afterwards treated this precipitate by the nitro-muriatic acid 

 compounded with the common acids used in commerce. 



Part of tlie matter only was dissolved, and there remained a 

 great quantity, over which the acid seemed to have no action, 

 although I had employed at least twelve parts. 



Presuming that this acid was too weak to act with efficacy on 

 the substance in question, I made a highly concentrated nifro- 

 muriatic acid, of which I applied six parts to one of this residue. 



On this occasion, the action v.as violent, and the solution was 

 very abundant even in the cold way, which was announced by a 

 brisk effencscence, adevelopment of abundanceof nitronsvapours, 

 an elevation of temperature, and the colouring of the liquor. AH 

 the matter however Avas not yet dissolved; there remaining at 

 least one-sixth, although the mixture had been long heated. 



Lastly, I once more poured upon this substance four parts of 

 the same nitro-muriatic acid: there was still a solution, Uit in 

 less abmuJance than in the foregoing operation, the proportion 

 being considered: I shall leave this residue for the present, hut 

 shall return to it ere long. 



Alth<uigh the substance treated as above tliree times with 

 nitro-muriatic acid had been previously subjected to the suc- 

 cessive 



