HYDKATES AND CARBONATES OF THE ALKALI METALS, ETC. 465 



the carbonic acid of the carbonate of rubidia, thus : — 2E 2 OC0 2 + Pt = Pt0 2 + 2R 2 4- 2CO. 

 If this is so, then the insoluble matter obtained from the crude chloride must be presumed 

 to have included chloroplatinate of rubidium. Supposing it contained nothing else, 

 the 3 mgrm. of ignited precipitate consisted of the mixture PtCl 2 E 2 , and indicated 2*8 

 mgrm. of Pt0 3 E 2 in the substance analysed. 



The platinum-free chloride contained less chlorine than the crude by 4 '8 mgrm., which 

 agrees well with the 5*08 demanded by the 7 mgrm. of dissolved platinum found for con- 

 version into PtCl 4 . The 3 mgrm. of insolubles correspond to 4*0 mgrm. of PtCl 6 R 2 . 

 Deducting these, and the 11 '8 mgrm. of dissolved chloride of platinum, we have 1508'0 

 mgrm. for the weight of the chloride of rubidium present as such or as chloroplatinate in 

 the soluble part of the crude chloride. But the chlorine in this, as we saw, amounted to 

 0-44267 = 12-485x01 mgrm. Hence we have RC1= 1508*0 : 12-485 = 120-78, and 

 R= 85*33, which agrees with the equivalent of unmixed rubidium. At this, however, 

 we need not wonder, as the caesium carbonate may well be presumed to have volatilised 

 during the ignition process. The carbonic acid found amounts to 256*1 = 11-641 x 22 

 mgrm. The total platinum found corresponds to 9'705 mgrm. of oxide = "08 5 x 0'5 Pt0 2 

 mgrm. 



Summing up, we have : — 



In Milligrammes, 

 absolute weight. 

 1166*54 

 256*10 

 9*705 

 6*957 



Total rubidia, E 2 0, . 



In Milligramme 

 equivalents. 

 12-499 



Carbonic acid, 



11-641 



Oxide of platinum, . 



0-085 



Water, as EHO, 



0-773 



Total, . . 1439*30 



The substance analysed weighed, .... 1433*60 



Excess found, . . . . . . .5*70 



which just about corresponds to the " water " found by calculation. It does not follow 

 that the water was absent, i.e., the surplus rubidia all present as platinite or anhydride. 



To avoid unnecessary repetitions, let me state that in the following experiments (III., 

 IV., and V.), when the carbonate was heated in dry nitrogen or carbonic acid, the product 

 was platiniferous, as in the case of Experiment II.; and had to be analysed by a similar 

 method. 



Experiment III. — 1*308 grm. of carbonate of rubidia were heated in the gas-crucible 

 over a Bunsen lamp in dry nitrogen for one hour. 1*0383 grm. of the product gave 

 1093*7 mgrm. of crude chloride, yielding 5'5 mgrm. of (ignited) insolubles. The chlorine 

 in the soluble part amounted to 318*02 mgrm; the chlorine in the platinum-free chloride to 

 316*99 mgrm.; difference, 1*03 mgrm. But the platinum found in the solution was 5*2 

 mgrm., demanding 3'78 mgrm. of chlorine for its conversion into tetrachloride. Hence 

 one at least of the two chlorine determinations cannot be quite correct, and, as we do not 

 know which it is that is at fault, we will deduct these 3*78 mgrm. of chlorine from the 

 318-02 found in the crude chloride, and adopt the mean between the remainder and the 



