CRITICAL EXPERIMENTS FOR DETERMINATION OF POTASSIUM, ETC. 599 



C. From the sal-ammoniac liquor ("IT.") ; determined in ignited residue as 



PtCl 6 K 2 , and as Pt eliminated from the same. Weight calculated from the 

 PtCl 6 K 2 was l - 22 ; from the Pt it was 1*60 mgs.; mean, 1*41 ; corrected for 

 the KC1 contained in the sal-ammoniac used,* 1*13 



D. The crude chloride of potassium, extracted from the crude chloroplatinate, 



weighed 241'5 mgs. According to the analysis of the filtrate from the 

 PtCl 6 K 2 obtained from it, it contained 657 mgs. of Na 2 S0 4 ; deducting this 

 we have — 



F. Pure chloride of potassium, 23493 



The pure chloroplatinate of potassium obtained from the crude chloride of 

 potassium was weighed ; its platinum extracted by H 2 in the wet-way, 

 and weighed likewise. 

 D . The KC1, calculated 



mean, 231-67 



From the PtCl 6 K 2 , was 231-48 



„ Pt „ 231-85 



This D then was the weight of chloride of potassium which the 

 Finkener process had actually separated out; the close correctness of 

 the number " A " was owing to the presence of foreign chloroplatinates 

 in what was nominally PtCl 6 K 2 . 

 E. In the analysis of the crude chloride of potassium, by means of the platinum 

 process, the little potassium which escaped precipitation was determined 

 as PtCl 6 K 2 , and calculated as KC1 ; found equal to .... 346 



To check the work, let us add up the various instalments of chloride of 

 potassium found. 



D +B + C + E, 237-0 



Excess found, . . . . 1*2 



F+B+C, 236-8 



Excess found, .... 1-0 



II. A Second Experiment differed from the (" I.") just detailed in the 

 following points : — (To the same quantity of sulphate of soda as had been 

 used in "I.") only 23-86 mgs. of chloride of potassium were added, and the 

 mixed solution Finkenerised with Jive times the calculated quantity of 

 platinum solution. The salt mixture (#Na 2 S0 4 + PtCl 6 K 2 ), after a final wash 

 with pure ether, was allowed to dry, and " recrystallised " without any 

 addition (of H 2 S0 4 , &c). In the treatment of the " recrystallised " salt 

 mixture (#Na 2 S0 4 + PtCl 6 K 2 ) with sal-ammoniac, an exhaustive extraction of 

 the sulphate was not insisted upon, for not decomposing too much of the 

 chloroplatinate of potassium. The impure residue obtained after treatment 

 with 90 grms. of sal-ammoniac solution was dissolved in hot water, the 

 platinum reduced out by H 2 and weighed. The sal-ammoniac liquor was 

 preserved. The results, so far, were as follows (in milligrammes) : — 



* Determined by a blank carried out on a large scale. 



