600 PROFESSOR DITTMAR AND MR JOHN M'ARTHUR ON 



Chloride of potassium used, including 0*29 mg., from 



TheNa 2 S0 4 2415 



Found. 



(Apparently) in the chloroplatinate-mixture, as calculated from the platinum 



extracted, 1918 



In the second ether-alcohol filtrates, 5 - 8 mgs. 



Of these 5"8 mgs. of platinum, however, 0-8 was present as PtCl 6 K 2 , hence the re- 

 crystallisation process, besides removing 5-8-0-8 = 5-0 mgs. of platinum present 

 as chloroplatinate, removed also - 8 mg. of platinum which ought to have 

 remained. 



Hence, if recrystallisation had not been resorted to, the chloride of potassium 



found would have been 23 - 59 



Errors in the actual and imagined determinations = -4 - 97 and - - 56 respectively. 



Experiment Ha. — The residue (?/Na 2 S0 4 + PtCl 6 K 2 + ~NH 4 C1) obtained in 

 the inexhaustive treatment with sal-ammoniac was, as stated, reduced with 

 hydrogen in the wet-way, to weigh the platinum present in it. The filtrate 

 from the platinum was evaporated to dryness, the residue made into sulphates, 

 and thus the original potassium — apart from what had gone into the two 

 ether-alcohol filtrates, and into the sal-ammoniac extract — recovered, as part 

 of a mixture of alkali-sulphates. This mixture was dissolved, Finkenerised 

 with only a small excess of platinum (50 mgs. of Pt instead of about 32 as 

 calculated), and no " recrystallisation " effected. The washed chloroplatinate 

 plus sulphate was treated exhaustively with sal-ammoniac (25 3 grms. 

 solution) ; the sal-ammoniac liquors being put aside. The chloroplatinate 

 ( + xNH 4 Cl) was dissolved in water, and the platinum reduced out ; it weighed 

 242 mgs., equal by calculation to 18 - 42 mgs. of chloride of potassium. 



The chloride of potassium was recovered from the filtrate : it weighed 

 18'4 mgs., including, however, 0*2 mg. of insoluble matter, hence corrected 

 weight = 18*2 mgs. It was dissolved in water, the S0 3 precipitated by 

 nitrate of baryta (precipitate calculated as Na 2 S0 4 = 0*29 mg.), and the 

 chlorine of the filtrate determined by nitrate of silver. Chloride of potassium 

 calculated from the weight of the chloride of silver = 1811 mgs. 



To be able to check our work, we determined the potassium in the two 

 ether-alcohol filtrates of Experiment II., and in the two sal-ammoniac liquors, 

 obtained in Experiments II. and Ha. respectively. 



Summary of Results. 



Mgs. 



Chloride of potassium taken, 2415 



KC1 present in the chloroplatinate of 11a. ; calculated from the Pt (242 mgs.) is, 18*42 

 The crude KC1 from the same, corrected by deduct- 

 ing S0 3 as Na 2 S0 4 . 1791 \ 



Calculated from the chlorine of the crude chloride of V . . . 1801 



potassium 1811 ) 



A = mean of 1842 and 1811, 18-27 



