W. Gihhs on the Platinum metals. 348 



8NH,C], are quite soluble in water. Oxydizing agents rendily 

 convert the proto-chlorid of ruthenium into sesqnichlond, wliich 

 is again precipitated in Chaus's process with IiCl^.KCl, in the 

 form of Eu,Cl3,2KCl. The portion of ruthenium which exists 

 in the mass of double chlorids in the form of RuCL,KCl may be 

 easily and almost completely removed by repeated and careful 

 washings with a cold and strong — but not saturated — solution of 

 chlorid of potassium, in which the salt, RuCl3,KCl, is soluble, 

 while the other double chlorids remain undissolved. The small 

 quantity of ruthenium dissolved in washing out the sesqnichlorid 

 of iron may be recovered by precipitating the iron carefully with 

 a solution of carbonate of potash, adding a slight excesvsof chlor- 

 tydric acid to the filtrate, and evaporating to dryness, when the 

 ruthenium salt remains mixed with a great excess of chlorid of 

 potassium. In Claus's process however this method is of little 

 use since the greater part of the ruthenium is removed in the 

 form of ruthenate of potash, while another portion remains as 

 fiu3Cl„2KCl, insoluble in chlorid of potassium. 



Another difficulty in Claus's process arises from the fact that 

 the rhodium salt, Rh^ClgjBNII.C!, is quite insoluble in a strong 

 solution of chlorid of ammonium, while a weak solution of the 

 ^ame salt dissolves a considerable portion of the iridium and 

 ruthenium salts, IrCl„KCl and Eu2Cl3,2KCL 



Claus's method of separating ruthenium— in the form of 

 EUjClj— from iridium, by adding a ^qv; drops of ammonia to 

 ^lie neutral solution and boding so as to precipitate Ru,03+a:H0, 

 gives good results when the quantity of ruthenium is large in 

 proportion to the iridium present, but not otherwise. Small 

 quantities of ruthenium cannot be separated at all by this process, 

 jor have I in any case been able to obtain iridium absolutely 

 free from ruthenium by boiling. For these reasons, while doing 

 f';i5l justice to the extraordinary skill and success of the Russian 

 «»emist, I have still thought the problem of the complete sepa- 

 ^ation of the metals of the platinum group worthy of a new in- 



,The method which I now use consists essentially in the em- 

 Poyment of the alkaline nitrites as separating agents; in addi- 

 f fi, however, I avail myself, as Glaus has so skillfully done, of 

 ^;je different degrees of' solubility of the double chlorids of the 

 P'^tmum and alkaline metals. 



, /lie relations of the alkaline nitrites to the pktinum metals 

 J^^ not hitherto been studied and require special attention in 

 ;,'"s place. The remarkable double salts which these metals 

 ';'[f^ when treated with the nitrites of potash and soda will be 

 ll^^iy described hereafter, but the general character of the salts 

 ^aemselves, upon which my methods of separation are based, 

 ^^y advantageously precede the details of their practical appli- 



