Memoir upon Palludiurh. and Rhodium. 35 



tina almost pure ; but I was puzzled for a few minutes as to 

 the true cause of this precipitation, by the sulphate of iron at 

 the mm'inuim producing the same etfect with tlie metallic iron. 



Tiiis suggested tlie idea, that in the solution of platiaa the 

 metal might be in two states of oxidation, and that at the viuii- 

 miirn was the only one precipitated by the sal ammoniac, while 

 the otiier remaining in solution was precipitated in its turn by 

 giving to the iron a portion of its oxvgen. In order to verify 

 this conjecture, I introduced into a vessel in which I had diluted 

 yellow salt of jdatina with water, oxy-muriatic acid gas, with 

 the intention of hvper-oxygenating this salt, if it was possible. 



The solution took place specdilv with a development of heat 

 and ciiange of colour, the liquid becoming red. A considerable 

 quantitv of gas was extricated, which 1 found to be azotic gas- 

 But when 1 put iron into this solution, no salt was precipitated 

 from it, but metallic platina ; the sulphate of iron produced no 

 effect on it : whereas the nmriate of ammonia, and ammonia it- 

 self, p.recipitated from it a great quantity of yellow salt. 



Thus the oxy-muriatic acid did not alter the state of oxida- 

 tion of the platina in its triple salt, but decomposed the am- 

 monia from it, and reduced it to the state of simple muriate : 

 it will follow that the sulphate of iron has, like the metallic iron 

 and the alkali-, the property of saturating a portion of the 

 acidity retained by the salt of platina in solution. The sul- 

 phate of iron boing decomposed by the muriatic acid, it is pos- 

 sible that the sulphuric acid, set free, has not under these cir- 

 cumstances the sanre solvent powers with the muriatic acid, over 

 the salt of platina. 



Lastly, t!ie fourth condition for obtaining, the salt of platina 

 pure, consists in diluting in a proper quantity of water the so- 

 lution of this metal, without which it will be very difficult to 

 wash the precipitate : it will always remain mixed with iron, 

 and other metals which exist in the same solution. It is better 

 that a greater quantity of salt of platina should remain in solu- 

 tion, than that the matter precipitated should be mixed with 

 foreign substances, because we ab.vays recover the platina in our 

 ulterior operations. Ten parts of water to one of the highly 

 concentrated solution, appear to me to be the proportion which 

 succeeds best, taking care to employ, in order to precipitate, 

 a solution of sal ammonia saturated cold. 



The annnoniacal nnniate of platina is not pure, except 

 when it is of a citron-yellow colour, when it does not become 

 brown upon drying, and when it pulverizes easily. 



§ III. Method of separating the Palladium J'rom the Rho- 

 dium and oilier nitluUic Salts, ivhich are united in the same 

 solution. — After having precipitated the platina by sal ammo- 



C 2 niac 



