CRITICAL EXPERIMENTS FOR DETERMINATION" OF POTASSIUM, ETC. 621 



iii the " platinum " was at the worst extremely small. The total weight of 

 platinum obtained amounted to 10923 grms. 



For the isolation of the fixed chlorine, the respective portion of the solu- 

 tion was evaporated to dryness, the residue dried at 130° for 2 hours, then dis- 

 solved in water, the solution re-evaporated, and the residue again dried at 130° 

 for 1^ hours. The solution of the thus dried salt was absolutely neutral to litmus. 



The determinations of the chlorine were effected by the " Challenger " 

 method as usual. 



Summary of Results. 

 Found per 2C1 = 70 - 91 parts of fixed chlorine. 



RCl by direct 

 weighing. * 



244-33 



These results at the time surprised us very much ; but we have no difficulty 

 now (after our later experience with the potassium salt) in explaining them. 

 Part of the 203*39 parts of platinum must be assumed to be present as 

 PtX 6 H 2 ; the X 6 including the 0816 x CI of chlorine, besides the necessary 

 amount of oxygen or hydroxyl. Taking Pt as 195 5 as it follows from our 

 potassium experiments, we have for the composition of 595*29 of the chloro- 

 platinate : — 



2KCI, 244-33 



Platinum. 



Loose Chlorine. 



Substance. 



203-39 



144-71 

 = 4-0816 x CI. 



595-29 



1-04036 xPt, . 

 Loose chlorine, 

 Hydroxyl, 

 Hydrogen, 



203-39 



144-71 



2-73 



008 



595-24 



01606 x OH. 



which agrees very well with the above 595-29 of substance analysed ; only the 

 closeness of the agreement is probably accidental, as the direct determination 

 of the " RCl " was made only on a very small scale.* 



We now pass to those synthetical experiments with standardised solutions, 

 of which, unfortunately, only the analytical parts are worth publishing. 



Experiment I. 



40 c.c of the rubidium solution were evaporated to 15 c.c, poured into 

 40*4 c.c. of standard platinum solution (1 c.c. = 49*5 mgs. of metal), and the 



* A weighed portion of the filtrate from the platinum evaporated to dryness, and made neutral, as 

 above explained, and weighed. Actual weight = -2213 grm. for the fraction analysed. The salt was 

 analvsed, and found to contain 29 - 09 per cent, of chlorine, i.e., almost exactly as much as the original 

 chloride of rubidium. 



