622 



PROFESSOR DITTMAR AND MR JOHN M'ARTHUR ON 



mixture was allowed to stand over night. Next morning the liquor was decanted 



through a small filter, the precipitate washed four times with water (10 c.c. 



each time), and then twice with absolute alcohol. Absolute weight of platinum 



used = 1*9976 grins.; platinum per Cl 2 = 70*91 parts of fixed chlorine == "P" 



= 201*8 (nearly, the exact data need not be reproduced here). Total chloro- 



platinate produced = 5*78 grms. It was dried at 130° C. for 5 hours, and then 



divided into two parts, A and B. A served for a determination of the water by 



the direct method, described page 578; water found = 0*862 per cent. B was 



reduced with hydrogen in the wet way (which took about 10 days), and analysed 



as usual. Found, per Cl 2 parts of fixed chlorine : alkyl chloride, by calculation 



from the percentage of chlorine in the original chloride of rubidium, = 243*79 ; 



platinum = 201*08; loose chlorine = 4*0776 x CI; chloroplatinate (dried at 



130°),= M == 593*81; hence, assuming that Pt — 195*5, and that only so much 



of the platinum is there as PtCl 6 R 2 > we have for M parts — 



Platinum, . 201*08 



243*79 



R 2 C1 2 , 



Other chlorine, 

 Hydroxyl, 

 Hydrogen, 

 Other water, . 



M., 

 Excess over M., 



144-57 

 1*59 

 0*06 

 4-28 



595*37 

 = 593-81 



= 1-56 



Experiment II. 



Conducted pretty much like Experiment I. Platinum used = 1*48 grms.; 

 P = 299. Chloroplatinate dried at 130° C. Water not determined. As the 

 reduction again progressed very slowly, the determination of the total chlorine 

 was omitted. Found per Cl 2 = 70*91 parts of fixed chlorine, M = 583*60 ; 

 platinum = 196*21 only, although such a large excess of platinum solution had 

 been employed for the production of the chloroplatinate ! Just as in the case 

 of the chloroplatinate of potassium, the presence of a large excess of chloro- 

 platinic acid seems to prevent precipitation of surplus platinum as Pt(OH) 6 H 2 ; 

 the basic salt, which would otherwise have clung to the precipitate, passes into 

 solution. Assuming that the loose chlorine in this case was double of the fixed, 

 we have, for the composition of M parts of chloroplatinate — 



R 2 C1 2 , 243*79 (calculated). 



Cl 4 141*82 



Platinum 196*21 



Water (?) 1*79 



583*61 



