Researches on the Salts of Selenious Acid. 



35 



SELENITES OF CALCIUM. 



l. Neutral: 3Ca.0 2 .SeO 4-4H 2 0. 



By mixing solutions of chloride of calcium and selenite of sodium, 

 a white precipitate is obtained in extremely small, microscopic prisms, uni- 

 ted in asteriated groups. 



Analyses: 



1) 0.4995 gr. salt, dissolved in the smallest possible quantity of hydrochloric 

 acid, gave, on adding sulphuric acid and alcohol, 0.3488 gr. sulphate of 

 calcium or 0.1436 gr. lime, and from the filtrate was precipitated 0.2 

 gr. selenium or 0.281 gr. selenious acid. 



2) 0.5243 gr. salt, treated in the same manner, gave 0.3655 gr. sulphate 

 of calcium or 0.1505 gr- linie and 0.208 gr. selenium or 0.2923 gr. se- 

 lenious acid. 



3) 0.345 gr. salt, kept over sulphuric acid, parted with 0.0125 gr. water. 



Centesimally represented: 



experiment theory 



1. 2. 



Lime 28.75 28.70 — 3CaO 168 29.32 



Selenious acid . . 56.26 55.75 — 3Se0 2 333 58.12 



Water (loss). . . 14,99 15.55 3.62 4H 2 72 12.56 



100.00 100.00 573 100.00 



The salt, which is brilliant white and satiny, dissolves in dry air 

 and then loses l / i of its water, according to 3). Berzelius has remarked 

 that this salt, when heated in glass-tubes, eats through the glass and runs 

 out in a fused state; a most remarkable effect, produced also by the salts 

 of magnesium and manganese. 



2. Diselenite : Ca.0 2 .SeO. + H 2 .0 2 .SeO. + H 2 0. 



A solution, obtained by the action of 1 mol. of lime on 2 mol. of 

 anhydride of selenious acid, on evaporating over sulphuric acid, afforded 

 very easily the salt in beautiful monoclinic prisms with basal end-faces 

 pyramid and dome-faces. It is pretty soluble in water and persistent in. 

 the air. 



