1814.] On Palladium and Rhodium. 219 



and the liquid assumed a red colour, while at the same time azotic 

 gas was disengaged ; but when I put iron into this solution, it pre- 

 cipitated no salt, but platinum in the metallic state. Sulphate of 

 iron produced no effect ; while sal ammoniac and ammonia itself 

 precipitated a great quantify of yellow salt. Thus oxymuriatic acid 

 did not alter the state of oxidation of the metal ; but decomposed 

 the ammonia, and thus reduced the triple salt to the state of a 

 simple muriate. Hence it follows that sulphate of iron, as well as 

 iron itself, nas the property of saturating a portion of the acid 

 which holds the tiiple salt in solution. The sulphate of iron being 

 decomposed by the muriatic acid, it is possible that the sulphuric- 

 acid set at liberty has not the same dissolving power on the triple 

 salt that the muriatic acid had. 



The {(Mirth observation which I shall make is to dilute the solu- 

 tion of the metal with a quantity of water. Without this precaution 

 it would be very difficult to wash the precipitate, and it would 

 remain mixed with iron and with tiie other metals that happen to 

 be present. It is better that the whole platinum should not be pre- 

 cipitated than that the precipitate .should be impure ; hi cause the 

 platinum remaining in solution is separated in the subsequent pro- 

 cesses. 



Ten parts of water and one of the solution in a state of great 

 concemration appear to me to be the best proportion. The 

 solution of sal ammoniac employed to precipitate ought to be 

 saturated. 



Ammonio-muriate of platinum is not pure unless it has a lemon 

 yellow colour, does not become brown iu drying, and is easily 

 reduced to powder. 



III. 



Method of separating the Palladium and Rhodium, and the other 

 Metallic Salts which are united in the same Solution. 



After having precipitated the platinum by meansofsal ammoniac, 

 1 put into the mother liquor plates of iron, in order to precipitate 

 the different metals which accompany platinum in its ore. 



I treated the black precipitate which I obtained successively with 

 cold nitric and muriatic acids. When these two acids ceased to act 

 I washed the residuum, and dried it. Daring this operation very 

 acrid white vapours rose; which 1 ascertained, by heating a portion 

 of the residuum iu a crucible, to be a mixture of calomel and mu- 

 riate of copper. The sublimate contained likewise globules of 

 wry, and a black matter, which 1 suppose, from the smell 

 which it exhaled, to be Osmium. 



The nitric acid which had been digested on the precipitate con- 

 tained much iron, some copper, and a small quantity of palladium, 

 though the digestion had taken place at the common temperature of 

 the air. 



The muriatic acid employed after the nitric contained likewise a 

 great deal of iron, some copper, and palladium, and cveu platinum 



