336 Professors Kirchhoff and Bunsen on Chemical 



c. Monocarhonatc of Rubidium. 

 This salt is best prepared from the sulphate of rubidium by 

 precipitating with baryta water, and evaporating the solution 

 of the caustic alkali to dryness with carbonate of ammonium. 

 The excess of baryta added remains behind on treating the 

 mass with water. The solution yields on concentration indistinct 

 crystals and crystalline crusts of hydrated carbonate of rubidium, 

 which, on heating strongly, melt in their water of crystallization, 

 and leave at last a porous mass, melting at a red heat, and 

 solidifying on cooling to an opake white crystalline salt. The 

 anhydrous salt is strongly hygroscopic, and dissolves in water 

 with evolution of heat. It has a caustic and corrosive action 

 upon the skin. The alkaline reaction of the salt is so powerful 

 that boiled water, to which only l0 Q 00 -ths of the salt has been 

 added, imparts a distinct alkaline reaction to red litmus paper. 

 The salt is almost insoluble in boiling absolute alcohol, 100 

 parts of alcohol only dissolving 0'74 of the salt. When fused 

 in a platinum crucible, it does not lose its carbonic acid, even at 

 very high temperatures. 1-4632 grm. of the salt which had 

 been fused for some time, lost 0-2748 grm. of carbonic acid 

 upon treatment with sulphuric acid. Hence the composition of 

 the salt is as follows : — 



Calculated. Found. 



RbO . . . 9336 80-93 81-22 



CO 2 . . . 22-00 19-0 7 18-78 



115-36 10000 100-00 



d. Bicarbonate of Rubidium. 



The aqueous solution of the monocarbonate is easily converted 

 into the acid salt when placed in contact with an atmosphere of 

 carbonic acid. If the solution be allowed to evaporate at the 

 ordinary atmospheric temperature over sulphuric acid, the salt 

 forms shining crystals, permanent in the air, possessing a pris- 

 matic form, but of which no sample sufficiently well crystallized 

 for exact measurement could be obtained. The crystals give a 

 very slightly alkaline reaction, and they possess a cooling, non- 

 caustic, agreeable taste, similar to that of saltpetre. On heating, 

 they easily lose the second atom of carbonic acid. They are very 

 soluble in water; and the aqueous solution gives off carbonic acid 

 on boiling, probably owing to the formation of a sesquicarbonate. 



0-5416 grm. of monocarbonate of rubidium was dissolved in 

 water in a weighed platinum crucible, and left for fourteen days 

 in an atmosphere of carbonic acid, which was slowly from time 

 to time renewed. After the solution had been evaporated at the 

 ordinary temperature over sulphuric acid, the mass was again 



