O. D. Allen on Caesium and Rubidium. 371 



spectroscope of ordinary power.* The rubidium salt was also 

 more carefully tested in the same manner, but was found to be 

 entirely pure. 



1 he process above described thus furnishes a simple and easy 

 method of separating in a perfectly pure state a large share (in 

 these trials about 90 per cent) of a mixture of the two alkalies. 

 It requires no great expenditure of time, since the solutions em- 

 ployed can ba concentrated at high temperatures, and on cooling 

 immediately deposit well formed crystals. 



Composition and solubility of the Biiartrates of Caesium and Ru- 

 6«cZtuw.— Bitartrate of rubidium crystallizes from hot solutions 

 in colorless transparent flattened prisms, which are often half an 

 inch or more in length, even when formed rapidly from small 

 quantities of solution. They remain unaltered in the air and 

 also are unchanged at a temperature of 100° C. The pulver- 

 ized salt dried at 100° C. was burned with chromate of lead in 

 ^ne usual manner. 



T A. 4 00 1 (0-0902 ffrm. water, and 



I. 4681 grm. gave ] o-354 " carbon i^ acid. 



To determine the base, the salt was heated to a temperature a 

 Jttle below redness, the resulting carbonate extracted with water 

 irom a small residue of carbon which could not be burned away 

 }vithout volatilizing rubidium. The carbonate was then converted 

 into chlorid, fused'^and weighed without exposure to the air. 



II. 1-3772 grm. gave 0-7149 grm. chlorid of rubidium. 



Iq the following statement these results are reduced to per 

 <=ents, and compared with the calculated composition of bitar- 

 trate of rubidium as expressed by the formula 



II Rbf*^* 



Oj, 8800 3r5o 



RbO 93-36 39-84 .... 40-09 



"234-36 100-00 

 The solubility of this salt in hot and cold water was deter- 

 Qiined by evaporatinc^ on the water-bath, solutions saturated at 

 ^te given temperatures and v---^-- ^^^ --.In- 



I- 11 -9254 grammes of solutic 

 f«sidue of 1-2555 grammes. 



