Researches on the Salts or Selenious Acid. 



27 



3) 0.4783 gr. salt gave off 0.1628 gr. water, when kept over sulphuric acid. 



4) 0.95 gr. of the salt that was obtained crystallized in large, four-sided 

 prisms, lost 0.324 gr. of its weight, when kept over sulphuric acid. 



Calculated on 100 parts: 



1. 2. 3. 4. 



Soda 23.50 23.43 — — 



Selenious acid .. 42.22 41.97 — — 



Water — '— 34.02 34.10, 



the formula requiring: 



Na 2 62 23.58 

 SeO 2 111 42.20 

 5H 2 90 34.22 

 263 100.00 



In waterfree state, this salt is obtained well crystallized in small, 

 milk-white, four-sided, quadratic prisms with basal end-faces, if the cry- 

 stallization takes place at a higher temperature 60° — 100°. 



0.453 gr. of this salt did not diminish in the weight, either in dry 

 air, or when heated to 100°, or when fused. 



By heating this salt, such as it was obtained after fusion, with sal- 

 ammoniac and weighing the remaining chloride of sodium, Berzelius deter- 

 mined its amount of soda to be 35.50 pr. ct.; the calculated quantity is 

 35.84 pr. ct. 



2. Neutral: Na 2 .0 2 .SeO. 



Muspratt says that he has not been able to obtain neutral selenite 

 of sodium crystallized with water from its aqueous solution ; may be he has 

 overlooked that this salt, when kept in dry air, loses the 5 mol. of cry- 

 stallization-water that it always contains, when allowed to crystallize at the 

 ordinary temperature, from a neutral solution. The material, on which he 

 undertook a soda-determination, was dried over sulphuric acid and then 

 contained 35.50 pr. ct. soda. It may also be very possible that it had not 

 deposited from a completely neutral, but from an acid solution, and, in this 

 case, waterfree selenite of sodium is obtained, as I had occasion to learn 

 in an attempt to ascertain, whether there existed any sesquiselenite of so- 

 dium. A solution, prepared for this purpose from 2 mol. of carbonate and 



