338 Professors Kirchhoff and Bunsen on Chemical 



rubidium, which acts rapidly upon the platinum vessels. Brought 

 into the colourless gas flame on a platinum wire, the salt is com- 

 pletely volatilized. It is much more soluble in water than salt- 

 petre ; 100 parts of water at 0° C. dissolve 20-1, and at 10° C. 

 43-5 parts of the salt. Under the same circumstances water only 

 dissolves 133 and 20-4 parts of saltpetre. 



2*3543 grins, of the salt, when decomposed by sulphuric acid, 

 yielded 2-1306 grins, of sulphate of rubidium. Hence the salt 

 consists of — 



Calculated. Found. 



RbO . . . 9336 63-35 6336 



NO 5 . . . 54-00 36-65 36-64 



14736 10000 10000 



f. Sulphate of Rubidium. 



The acid salt having the formula RbO, 2 SO 3 fuses like the cor- 

 responding potassium salt near redness, and when more strongly 

 heated froths considerably, losing half its sulphuric acid, and 

 leaving a solid residue, fusible only at a white heat. If the 

 aqueous solution of this neutral salt be slowly evaporated, fine 

 large hard brilliant crystals are obtained, which belong to the 

 rhombic system, and possess a ratio of the axes of a : b : c as 

 0*5723 : 1 : 0-7522, corresponding to a rhombic octahedron 

 whose basal angles are 113° 6', and whose polar angles are 

 131° 6' and 87° 8'. The crystal represented in fig. 2 gave the 

 following surfaces : — 



o — o 

 o — o 



s~o 

 s — A'i 



P.QO.P2. 





Found. 



Calculated. 



131 6 





113 6 



O / 



130 36 



130 42 



112 43 



112 46 



This salt is therefore isomorphous with sulphate of potassium, 

 which, according to Mitscherlich, possesses the following ratio 

 of the axes :— a : b : c as 0-5727 : 1 : 0-7464. The sulphate of 

 rubidium is anhydrous, perfectly unalterable in the air, and it 

 possesses a peculiar taste, resembling that of sulphate of potas- 

 sium. On heating, it decrepitates, and loses its tranparency. 

 Placed on a platinum wire in the flame, it is completely volatilized. 

 100 parts of water at +70°C. dissolve 42'4 parts of this salt ; 

 under the same conditions only 9*58 parts of svdphate of potas- 

 sium are dissolved. 



1-0098 grm. of this salt yielded 0-8872 grm. of sulphate of 

 barium. Hence it consists of — 



