466 PROFESSOR W. DITTMAR ON THE BEHAVIOUR OF THE 



316*99 found directly for the platiuum-free chloride as representing the true value for 

 the latter. This mean is 315 -61 = 8 '9018 x CI mgrm.; so many equivalents of rubidia 

 were in the soluble part of the chloride. In addition thereto, if we view the 5*5 mgrm. 

 of ignited insolubles as consisting of PtCl 2 R 2 , we have, for this residue, 2*33 mgrm. of R 2 

 and 2*85 mgrm. of oxide of platinum. The carbonic acid amounted to 197*0 mgrm. 

 Hence we have — 



In Milligramme In Milligrammes, 



equivalents. 

 Eubidia, B, 2 0, . . . 8-9267 



Carbonic acid, . . . 8*9547 



Oxide of Platinum, . . 0-0780 



absolute weight. 

 8331 * 

 197-0 

 8-9 



. 1039-0 

 . 1038*3 



Total, 



Substance analysed, 



which agrees satisfactorily, but the equivalents of acid and of base do not balance each 



other. Remembering that the number for the carbonic acid by itself is uncertain by 



± half a mgrm., and consequently the corresponding quotient by ±0*023, the analysis 



may be read as showing that the product was normal carbonate of rubidia mixed with 



oxide of platinum. 207 mgrm. of the product were handed to Mr Henderson for the 



determination of the free base by the chloride of barium process. He found 0*07 mgrm. 



of Rb 2 0, or 0*03 per cent. But this corresponds to only a drop of the very dilute acid 



used ; hence what he really made out was that the product contains a just perceptible 



trace of free base. 



Experiment IV. — Not feeling quite sure of the result of the last experiment, I 

 repeated it with 1*838 grm. of carbonate, with this difference, however, that I handed the 

 whole of the product to Mr Henderson for the determination of the free alkali by the 

 chloride of barium method. He found, in 1*785 grm., 2*79 mgrm. of Rb 2 0, or 0*156 per 

 cent. This, of course, includes the platinite, which must be presumed to have been present. 



Experiment V. — In this experiment 2*356 grm. of the carbonate were heated in the 

 gas-crucible over a Bunsen in a current of dry carbonic acid for one hour. 1*3382 grm. 

 of the product, when treated with hydrochloric acid, gave 252*0 mgrm. of carbonic acid 

 = 11*455x22 mgrm., and 1409*6 of crude chloride, containing 2*0 mgrm. of (ignited) 

 insolubles, and, in the soluble part, 411*52 mgrm. of chlorine = c', and 1*0 mgrm. of 

 platinum, demanding 0*73 mgrm. of chlorine for its conversion into tetrachloride. 

 The platinum and HCl-free solutum contained c" = 410*70 mgrm. of chlorine, 

 = 11*548 x CI. Now, c' — c" = 0'82 mgrm., which is a sufficient approximation to 0*73. 

 The 2*0 mgrm. of insolubles (if PtCl 2 R 2 ) correspond to 2*65 mgrm. of chloroplatinate ; 

 hence the weight of the platinum-free chloride, calculated from the crude, is 

 1409*6- (2*65 4- 1*73)= 1405*2 mgrm.; hence RC1= 1405*2 : 11*584 = 121*31 ; whence 

 R = 85*85 and J>R 2 = 93*85. The 2 mgrm. of ignited insolubles correspond to 0*83 

 mgrm. of rubidia = 0*009 eqq., and to 1*04 mgrm. of oxide of platinum. The total 

 platinum oxide amounts to 2*20 mgm., = 0*019 x ^Pt() 2 . Hence we have — 



* R = 85 , 33, as found in Experiment II. 



