G20 PROFESSOR DITTMAR AND MR JOHN M'ARTHTJR ON 



Hence our " chloride of rubidium " contained 



Real chloride of rubidium, 96 - 985 



Chloride of aesium, ....... 3-015 



100-000 



These 3 per cent, of caesium chloride, although inconvenient, did not 

 unfit the salt for our purpose ; all we had to do was to base our calculations 

 of " Pt " not upon the weight of alkyl-chloride present in the respective chloro- 

 platinate, but upon the weight of the chlorine in that chloride. 



The reason why we took such pains in standardising our rubidium solution, 

 of course was, that we intended to rely chiefly on the synthetical data of our 

 experiments ; but unfortunately, these became almost valueless through a 

 change in the strength of the rubidium solution, which was observed only 

 after the greater part of the work had been completed; yet they were, and still 

 are, of great use to ourselves as affording checks for the respective analyses. 

 Only the latter are reported on in the following paragraphs : — 



To begin with a case where no quantitative synthesis was attempted, let 

 us give the results of an analysis of the chloroplatinate of rubidium referred to 

 above, as having been obtained incidentally from about 5 grms. of salt. 



3 2495 grms. of this preparation (weighed after a preliminary drying at 



120° C.) were placed in a " Geissler tube," and dried systematically, first at 



120°, then at 130°, and lastly at 150° C. The weights recorded were as 



follows : — 



After 2 hours at 120°, 3-2457 



130°, 3-2432 



„ 9 „ 150°, 3-2342 



Even then the weight was not constant ; yet the drying process was stopped, 

 and 3*1970 grms. of the salt transferred to an Erlenmeyer flask, to be reduced 

 with hydrogen in the wet way, and analysed in the way we had before applied 

 to many specimens of the potassium salt. 



The reduction set in very readily, but was very slow in coming to an end. 

 It took in all about six days for its completion, although every morning the 

 precipitate was broken up with a glass rod, to bring the hidden chloroplatinate 

 to the surface. When at last the reduction seemed to be completed, the 

 platinum was filtered off, and the filtrate divided gravimetrically for the deter- 

 mination of the fixed and of the total chlorine. Suspecting that the platinum 

 might include some undecomposed chloroplatinate, the greater part was 

 removed from the filter, and next dehydrated at a dull-red heat. It weighed 

 1-0454 grms.; after subsequent strong ignition this weight was 1-0452 

 grms. and after a succeeding strong ignition in hydrogen it was 10449 

 grms. Hence it appears that the proportion of undecomposed chloroplatinate 



