CRITICAL EXPERIMENTS FOR DETERMINATION OF POTASSIUM, ETC. 631 



What value must we assign to Pt, so that the (OH) 6 H 2 , combined with the 

 surplus platinum (197 07 — Pt) equals these 3*63 parts ? 



An easy calculation shows that we must take Pt = 190*4, which, of course, 

 is quite inadmissible, but part of these 3*63 parts may be water. 



III. Series. 



The Experiments reported on under I. and II. were made a good long time 

 ago. Quite lately, when we were engaged in summing up results generally, it 

 struck us that they had better be supplemented by new experiments made 

 with a chloroplatinic acid prepared from metal by means of hydrochloric acid 

 and chlorine gas, and we accordingly did so. The following three syntheses 

 and analyses were made with the same kind of sal-ammoniac as had served for 

 Series I. and II., and the general modus operandi was the same as in Series I. 

 The ether-alcohol washings were subjected to distillation to remove the ether- 

 alcohol, the residue mixed with water, the platinum reduced out by hydrogen, 

 and the mixture produced distilled with ammonia-free caustic soda, so as to 

 concentrate the ammonia into a small quantity of hydrochloric solution. This 

 solution was mixed with chloroplatinic acid, evaporated to dryness, and the 

 residue washed with ether-alcohol, &c, to recover the ammonia as chloro- 

 platinate. The weight of sal-ammoniac operated upon in each experiment was 

 about 0814 grm., the weight of platinum used per 2NH 4 C1 was 227 parts, or 

 about 1-15 times the quantity demanded by Pt = 197. The chloroplatinate 

 precipitates were dried at 100° C. until constant in weight. 

 The results are given in the following tables : — 



Experiment, (1) 





(2) 



(3)* 



Sal-ammoniac taken, 



. -81359 





■81388 



•81352= A. 



Sal-ammoniac in ether-alcohol filtrate, '00083 





•00083 



•00160 



„ in precipitate, . 



. -81276 





•81305 



•81192 = A 



Chloroplatinate obtained, 



. 3-4179 





3-4139 



3-4063 =C. 



Platinum in C, 



. 14925 





1-4940 



1-4883 =p. 



Total chlorine, 



1-61684 





1-61865 



1-61525 



A :C, 



. -23804 





•23840 



•23883 



A : C, 



•23780 





•23816 



•23836 



A :p, 



•54512 





•54476 



•54661 



K'-P> 



•54456 





•54421 



•54553 



p : C, 



•43667 





•43762 



•43693 



Platinum per 2NH 4 C1 (from A ), . 



196-51 





196-64 



196-16 Pt 



„ per 6 x CI, 



196-15 





196-35 



196-01 Pt' 



Sal-ammoniac (A ) per 6 x CI, 



106-82 





106-85 



106-93 



From (1) and (2), chloroplatinate 



^ 





/ 







~Y~ 







per2NH 4 Cl, .... 



449-68 







Ditto ; total chlorine, . 



213-08 



= 6-0099 x CI. 





* This experiment was carried out for us by Mr James Robson. 



