W. Gihhs on the Platinum metals. 



platinum. The double chlorid of mercury and ruthen-diamin 

 has the formula 2NH3,RuCl + HgCl ; it is" almost insoluble in 

 cold water, but is soluble in boiling water and is easily rendered 

 absolutely pure bj recrystallization. On ignition this"'salt yields 

 chemically pure metallic ruthenium as a silyer-white porous 

 mass. When, in a mixture of solutions of ruthenium and pla- 

 tinum, the ruthenium is present either partly or wholly as ses- 

 quichlorid, the liquid is to be boiled with nitrite and carbonate 

 of potash as above, evaporated to dryness, boiled with excess of 

 chlorhydric acid to convert the double nitrite of ruthenium and 

 potassium into chloro-ruthenate of potassium, RuCl2,KCl, and 

 the resulting solution treated by the process already described. 



Platinum from rhodimn.—The separation of these metals may 

 be approximately effected by bringing the platinum into the form 

 of PtCl„KCl or PtCU,NH,Cl, Snd the rhodium into that of 

 Eh3Cl3,8KCl, or Bh3Cl3,3NH,Cl, and then carefully washing 

 out the rhodium salt by small successive portions of cold water 

 or better of a moderately concentrated solution of chlorid of 

 potassium or ammonium. This is the method usually employed. 

 By recrystallizing the platinum and rhodium salts respectively 

 they may be obtained in a state of purity, since they are not iso- 

 morphous. To obtain rhodium absolutely free from platinutn it 

 is best to convert the two metals into the ammonium double salts, 

 separate the rhodium salt as completely as possible by washing 

 with a solution of sal-ammoniac and then evaporate the double 

 chlorid of rhodium and ammonium with a solution of ammonia. 

 In this manner the rhodium is converted into the chlorid of the 

 ammonia-rhodium base discovered bv Claus, b^B-^^^^^i^^v 

 while the platinum forms no well defined or crystallizable com- 

 pound. The chlorid of Claus's base may theii be purified by 

 repeated crj^staUization. 



Iridium from rutheniur, 

 not be effected by igniting them ^ 



caustic potash. "Under these circumstances the ruthenium is 

 oxydized to ruthenate of potash, but a portion of the iridium also 

 becomes soluble in the alkali, though in what state of oxydation 

 it is difficult to ascertain. Moreover the complete oxydation ot 

 a mixture of the two metals, even when in a finely divided state, 

 can hardly be effected by a single fusion. Claus has given no 

 general method for the separation of iridium and ruthenium -in 

 the wet way. In his method of treating the Siberian ores the 

 greater part of the ruthenium is separated as ruthenate of potostt 

 by the primary fusion with saltpeter and caustic potash, but a 

 portion always remains with the iridium and is diSicult to remove, 

 .^specially as, after solution in chlorhydric acid, salts of both ses- 



