1G 



L. F. Nilson, 



commonly their acute combination- edges between the prism-faces and the 

 basal end-faces truncated and, besides, exhibit several other combinations. 

 The salt is very deliquescent, but becomes opake in contact with dry air. 



Analyses: 



1) 0.465 gT. salt gave 0.1673 gr. selenium or 0.2351 gr. selenious acid 

 and 0.2843 gr- sulphate of rubidium or 0.199 gr. rubidia. 



2) 0.4215 gr. salt gave 0.152 gr. selenium or 0.2136 gr. selenious acid and 

 0.257 gr. sulphate of rubidium or 0.18 gr. rubidia. 



Calculated on 100 parts: 



experiment theory 



1. 2. 



Rubidia 42.80 42.70 V 2 Rb 2 93.4 43.79 



Selenious acid. . . 50.56 50.68 SeO 2 111.0 52.01 



Water (loss) . . . ._6.64 __6_.62 ] / 2 H 2 9.0 4.20 



ToTloo loo.oo 213T4 100.00 



The analysis has given too low values of alkali and acid, owing to 

 the hygroscopic tendency of the salt; the composition here assumed is not, 

 however, subject to the least doubt, as agreeing with that of the correspon- 

 ding salt of potassium. 



3. Tetiuselenite: RbH.0 2 .SeO + H 2 .0 2 .SeO. 



A solution of this salt was prepared by decomposing 1 mol. car- 

 bonate of rubidium with 4 mol. selenious anhydride. Being evaporated over 

 sulphuric acid until it had the consistency of a thick syrup, it yielded a 

 salt in long prisms, united to a radiate crystal-cake, in which the form of 

 the individual crystals was not to be ascertained. It is permanent on ex- 

 posure to the air. Like the acid alkaline salts in general, it easily receives 

 a reddish tint from partially reduced selenium. 



An aly ses: 



1) 0.616 gr. salt gave 0.283 gr. selenium or 0.3976 gr. selenious acid, the 

 rubidium estimation was lost. 



2) 0.52 gr. salt gave 0.239 gr. selenium or 0.3358 gr. selenious acid and 

 0.198 gr. sulphate of rubidium or 0.1387 gr. rubidia. 



