CRITICAL EXPERIMENTS FOR DETERMINATION OF POTASSIUM, ETC. 569 



potassium determined only synthetically; the platinum both ways. Besults, 

 referred to 2KC1 parts, were — 





Platinum. 



unioropiaun 

 110°. 



ate, anea at 



130°. 



Synthesis, . 



19571 



488-43 (= M') 



488-28 ( = M") 



Analysis, . 



195-63 







Hence, by calculation, P = 19567, and PtCl 6 K 2 -= 486*67. Hence water, &c. 

 in M', =1-76 parts, or 0-360 per cent. 

 in M", =1-61 „ 0330 



Experiment III. (Matthey's Metal). 



A = 1*85556; P = 206*4 parts. The two reagent solutions were evaporated 

 separately to about 30 c.c. each, and then mixed ; the platinum being poured 

 into the potassium salt. Mixture evaporated to 5 c.c, and allowed to stand 

 over night. The precipitate washed by decanting filtration with three 

 instalments of water, each = 3 c.c; 15 c.c of absolute alcohol were then added, 

 and the precipitate washed with absolute alcohol. The precipitate was dried 

 at 130°, first for 5 hours, and then for other 24 hours ; and in part of the final 

 residue the ivater was determined directly (see page 578). The combined 

 chloride of potassium was determined only by synthesis ; the platinum both 

 ways. Found per 2KC1 parts, 



Platinum, by synthesis, = 195*75 "j 



Platinum, by analysis, = 195-56 J 



and for the weight of the chloroplatinate : — 



Dried at 130° for Anhydrous, by water 



5 hours. 29 hours. determination. 



M' = 487*78 M" = 487*29 M"' = 486-63 



From Pt = 195*66; by calculation, PtCl 6 K 2 = 486*66 ; hence water, &c, 



112 0-63 -003 



or 0-230 0129 nil per cent. 



Experiment IV. (Matthey's Metal). 



This experiment was wrought side by side of Experiment III., on the same 

 scale, and in the same way, except that the chloride of potassium was poured 

 into the platinum, and that the excess used of the latter was a little greater. 

 The two chloroplatinates were dried, side by side, in the same chamber, only 

 while, after 29 hours at 130°, No. III. was taken out to be analysed, No. IV. 

 was dried for an additional 12 hours at 150°. The water in the finally dried 

 substance was determined directly (see page 578). During the heating process 

 involved in the determination of the water, the salt decrepitated so much, that 

 a reduction of the residue in hydrogen could not have been effected with 



VOL. XXXIII. PART II. 4 P 



