I 



28 L. F. Nilson, 



3 mol. of selenious anhydride, afforded, after evaporation to a syrupy mass, 

 a salt in the crystalline form of waterfree selenite of sodium. 



Analysis: 



0.6 gr. salt gave 0.2715 gr. selenium or 0.3815 gr. selenious acid and 

 0.459 gr. sulphate of sodium or 0.2004 gr. soda. 



In 100 parts: 



experiment theory 



Soda 33.42 Na 2 62 35.84 



Selenious acid . . . . 63.58 SeO 2 _111 64.1 6 



97.00 174 100.00 



The compound thus obtained was consequently a waterfree selenite 

 which, to judge from the analysis, must have been in some measure con- 

 taminated with diselenite; in fact, this salt began afterwards to crystallize 

 in large quantities. For this reason, it seems as if no sesquiselenite could 

 be formed. 



3. Diselenite: NaH.0 2 .SeO. 



Prepared as the corresponding selenite of potassium, this salt cry- 

 stallizes from its solution, when considerably concentrated, in radially arran- 

 ged groups of probably monoclinic prisms, combined with basal end-face, 

 pyramid of another order, hemi-pyramid- and hemi-dome-faces. The crystals 

 have a cuneate appearance and a strong tendency to form radiate aggregates. 

 The salt is permanent, both in ordinary and dry air and also at 100°, at 

 which temperature it does not fuse. In water, it is very soluble. 



Analyses: 



1) 1.2343 gr. salt gave 0.644 gr. selenium or 0.9049 gr. selenious acid and 

 0.5803 gr. sulphate of sodium or 0.2533 gr. soda. 



2) 1.217 gr. salt gave 0.635 gr. selenium or 0.8923 gr. selenious acid and 

 0.5718 gr. sulphate of sodium or 0.2497 gr. soda. 



3) 1.5314 gr. salt showed undiminished weight, when kept over sulphuric 

 acid and, likewise, on heating to 100°. 



