CEITICAL EXPERIMENTS FOR DETERMINATION OF POTASSIUM, ETC. 577 



"A" was used for a direct determination of the water. 1-3573 grms. of 

 substance gave 1*1 mgs., or 0'081 per cent. " B " and " C " were analysed by 

 wet-way reduction. Found for 



"B." "C." Mean. 



Substance, .... 1-0990 1-5917 



Platinum obtained, . . . 04416 06403 



Substance per 1 grm. of platinum, 2-4887 2-4859 2-4873 



The agreement being satisfactory, the nitrates from the platinum were 

 mixed, and used for the determination of the fixed, and of the total, 

 chlorine. 



Results. — Substance = 2-6912 (by direct weighing preceding the dividing into 

 "B" and "C"). Total chlorine [calculated from the mean of 023554 and 

 0-23582] = 1 17466. Fixed chlorine [calculated from the mean of 023462 and 

 0-23501] = 039223. 



Hence per 2KC1 parts : — 



Substance. 

 Platinum. Total Chlorine. Dried at 100°. Anhydrous. 



M'. M". 



195-59 212-362 = 5-9896 x CI. 486-53 48614 



Neglecting the small chlorine-deficit, we have for the sum of components 

 486'59, which, singularly, agrees better with M' than with M". Perhaps the 

 11 mgs. of water found in "A" was the result of observational errors, — water 

 absorbed after weighing of the substance, or water out of the joints, &c. 



In the preparation of the two chloroplatinates VIII. and IX. we were 

 very much struck by the promptitude with which they acquired a constant 

 weight in the drying chamber ; all our previous chloroplatinates used to 

 continue losing weight for hours and hours, and hardly ever really exhibited 

 absolute constancy of weight. 



The most remarkable feature in these chloroplatinates, however, is, that 

 although produced in the midst of a very large excess of chloroplatinic acid, 

 they contained rather less platinum per 2KC1 parts than we had found in the 

 chloroplatinates previously produced in the presence of small excesses, or even 

 negative excesses, of the platinic reagent. Yet it does not follow that even 

 those quasi-exceptional chloroplatinates (of Experiments VIII. and IX.) were 

 free of surplus platinum. At the time when Experiments VIII. and IX. 

 were planned, this question had already been expiscated experimentally to 

 some extent by special experiments on chloroplatinates V. and Va., which 

 were done at the time when the analysis of V and Ya. were carried out, but 

 which we prefer, in this memoir, to treat of separately in the following 

 section. 



VOL. XXXIII. PART II. 4 Q 



