342 W. Gihhs on the Platinum metals. 



and possibly a trace of palladium. When the washing with 

 chlorid of potassium has been carefully executed with a cold and 

 saturated solution, the quantity of ruthenium dissolved is too 

 small to be worth separating. It only remains therefore to sep- 

 arate the metals in the mass of mixed double chlorids. Plati- 

 num and iridium exist in this mass in the form of bichlorids, as 

 PtCl^.RCl and IrCi„KCl ; ruthenium is present partly assesqui- 

 chlorid and partly as bichlorid, Ru,Cl3,2KCl and EuCL.KCl; 

 rhodium ap|)ears to be present only as sesquichlorid, PhjCl,, 

 3KC1, so far at least as it is possible to determine. The separation 

 of these metals from each other is a problem of no ordinary 

 difficulty. ^ 



Of ih^e methods which have been proposed for this purpose 

 I have no hesitation in saying that that of Claus is the only one 

 which yields the different metals in a state of purity. In fact 

 after a long and laborious study of the subject I believe that no 

 other chemist hns worked with pure preparations of iridium and 

 rhodium, the descriptions even of Berzelius ajiplying only to 

 mixtures of isomorphous salts in various proportions. In addi- 

 tion the discovery of ruthenium by Claus rendered a complete 

 revision of the subject necessary. Such a revision Claus has 

 himself uiven in his elaborate and most valuable memoir already 

 cited.* For the details of Chaus' processes I must refer to his 

 pnper. In principle his method consists in separating osmium 

 and ruthenium by fusion with a mixture of caustic potash and 

 saltpeter ; cold water then dis.solves out osmate and ruthenate of 

 potash. The residual mass consists chiefly of the oxyds of 

 iridium, rhodium and platinum. These, after distillation with 

 aqua-regia, are brought into the form of double chlorids with 

 ammonium; the iridium reduced to sesqnio.xyd by means ot 

 sulphydric acid, and the platinum separated from the other two 

 metals by washing with a strong solution of sal-ammoniac, ^he 

 filtrate from thechlorplatinateorammonium contains iridium and 

 rhodium as sesquichlorids; the iridium is converted by chlorine 

 and nitric acid into bicldorid, and the insoluble chloro-iridateot 

 ammonium separated by filtration from the soluble rhodium salts. 

 This method has given excellent results in the bands of its author 

 but is not free from objection, the chief difficulty lying, in ^T 



■i separation of ruthenium from i 



!,C1„2KCI is scarcely to be d 

 ;«iiiun;e uom the iridium salt IrCl.,,KCl; it posses.ses aoouu "- 

 ame degree of solubility in water and in solutions of chlond ot 



2KCI is scarcely to be distinguished ] 



potassium and ammonium. By the action of reducing agents t 

 sesquichlorid of ruthenium is reduced, apparently to a proto- 

 eUorid, the double salts of which, like Ir Cl3,SKCl and Ir,Cl„ 



Dorpat, 1854. 



