18 



L. F. Nilson, 



2. Diselenite: CsH.0 3 .SeO. 



A solution, obtained by treating 1 mol. carbonate of caesium with 2 

 raol. selenious anhydride, having assumed the consistency of syrup, afforded 

 the diselenite in small, oblique, four-sided tablets, often six-sided the 

 acute angles being truncated, rarely forming long prisms. The salt is 

 deliquescent on exposure to the air, but not in so high a degree as the 

 neutral salt. It was prepared for analysis by pressing and subsequent 

 drying over sulphuric acid under the receiver of the airpump. 



Analyses: 



1) 0.679 gr. salt gave 0.2005 gr. selenium or 0.2817 gr. selenious acid and 

 0.4665 gr. sulphate of caesium, corresponding to 0.3634 gr. oxide of 

 caesium. 



2) 0.6945 gr. salt gave 0.206 gr. selenium or 0.2895 gr. selenious acid 

 and 0.4765 gr. sulphate of caesium, corresponding to 0.3712 gr. oxide of 

 caesium. 



Calculated on 100 parts: 



experiment theory 



1. 2. 



Oxide of caesium. ... 53.52 53.45 V 2 Cs 2 141 54.02 



Selenious acid 41.49 41.68 SeO 2 111 42.53 



Water (loss) 4.99 4.87 7 2 H 2 J) 3.45 



100.00 100.00 261 100.00 



3. Tetraselenite: CsH.0 2 .SeO + H 2 .0 2 .SeO. 



This salt, deposited easily from a solution, containing 1 mol. oxide 

 of caesium to 4 mol. selenious anhydride, in large, four-sided, laminar cry- 

 stals, remains unaltered on exposure to the air. 



Analyses: 



1) 0.5 gr. salt gave 0.199 gr. selenium or 0.2797 gr. selenious acid and 

 0.2288 gr. sulphate of caesium, containing 0.1782 gr. oxide of caesium. 



2) 0.5385 gr- salt gave 0.217 gr. selenium or 0.3049 gr. selenious acid 

 and 0.248 gr. sulphate of caesium, containing 0.1932 gr. oxide of 

 caesium. 



