[archibald-kern] solubilities OF THE CHLOROPLATINATE 9 



viz., Precht\ Dithmar and McArthur-, Noyes and Weber^, Archibald, 

 Wilcox, and Buckley^. The solution of chloroplatinic acid thus 

 prepared was diluted and treated with a saturated solution of ammon- 

 ium chloride. The precipitate obtained was of a slightly reddish 

 tinge showing that a little iridium must have been carried down, 

 indicating that the elimination of the nitric acid was not as comlpete 

 as we had hoped. The mother liquor, however, was of a dark brownish 

 red color showing that the greater part of the iridium had remained 

 in solution. The precipitate was washed with absolute alcohol, 

 dried and reduced to platinum black in a current of hydrogen. Upon 

 dissolving the reduced platinum in aqua regia an insoluble residue 

 remained, which further indicated that iridium had been carried 

 down in the first precipitation. After expelling the nitric acid, 

 somewhat more thoroughly, perhaps, than was done before, the 

 platinum was again thrown down as chloroplatinate. The appear- 

 ance of the precipitate at this stage led us to think that all the iridium 

 had been left behind and this belief was strengthened by the absence 

 of any residue when the platinum resulting from the reduction of the 

 precipitate was dissovled in aqua regia. Nevertheless, as we wished 

 to have a very pure salt for these measurements another precipitation 

 of the chloroplatinate was made and again the salt was washed, 

 dried and reduced. 



That we might dissolve the platinum without introducing any 

 nitric acid we now made use of the method suggested by Weber^ and 

 modified by one of us^ whereby the finely divided platinum black is 

 made the anode in an electrolytic cell of which strong hydrochloric acid 

 is the electrolyte. A current of one ampere is passed through the 

 cell and practically all the chlorine attacks the platinum forming 

 platinic chloride. When all the platinum had dissolved, the solution 

 was evaporated to 100 c.c, expelling some free chlorine, then diluted 

 to 200 c.c. and the platinum precipitated with a strong solution of 

 ammonium chloride. This precipitate was washed on a Gooch 

 crucible with absolute alcohol, dried at a low temperature and was 

 then ready for use. 



Ammonium Bromoplatimate : A portion of the pure platinum 

 black, prepared as described above, was used for the preparation of the 

 ammonium bromoplatinate. The process was the same as for the 



1 Zeit Anal. Chem., 18, 509, (1879). 



2 Trans. Roy. Soc. Edin., 33, 561 (1887). 

 « Jour. Am. Chem. Soc, 30, 13, (1908). 



* Jour. Am. Chem. Soc, 30, 747, (1908). 

 6 Jour. Am. Chem. Soc, 30, 29, (1908). 



• Loc. Cit., p. 730. 



