74 



L. F. Nilson, 



in this paper, mercurous oxide is the only one, from which I have not 

 been able to obtain a neutral selenite. 



B) MERCURIC SELENITES. 

 1. Neutral: Hg.0 2 .SeO + H 2 0. 



Berzelius, by dissolving mercuric oxide in selenious acid, obtained 

 this salt in the form of a white powder, sparingly soluble in water. Kohler 2 ), 

 who employed oxide both precipitated and prepared by heat, was, however, 

 not able to arrive at such a result, either in low or high temperature, but 

 obtained a white-yellow, amorphous product, which he, on account of a 

 communicated analysis, regards as a basic salt: Hg 7 .O u .4SeO; but it is, 

 most surely, nothing else than a neutral salt, mixed with still unaltered 

 mercuric oxide, and for that reason yellow-coloured. 



I found, namely, Berzelius' statements in this respect confirmed. 

 When precipitated mercuric oxide was treated with a solution of selenious 

 acid, no change was observed; but when the solution was allowed to 

 evaporate at 100°, the acid thus becoming more concentrated, the yellow 

 colour gradually disappeared, and there was at last obtained a completely 

 Avhite salt of small prisms, which, under the microscope, seemed to be 

 six-sided with obliquely cut ends. A considerable excess of selenious acid 

 was employed for the reaction ; the mother-liquor, on evaporation, afforded 

 a product, crystallizing in large, flat, rifled prisms. On account of Berzelius 

 description of a diselenite, obtained by him, I thought this to be such a 

 salt; but, when examined, it proved to be free selenious acid, with no ad- 

 mixture of mercuric oxide. 



The salt was prepared for analysis by washing with water and de- 

 siccating between folds of bibulous paper. 



Analyses: 



1) 0.766 gr. salt, dissolved in hydrochloric acid, hydrosulphuric acid being 

 passed into the solution and the obtained precipitate digested with 

 cyanide of potassium, gave a residue of 0.5075 gr. mercuric sulphide 

 or 0.4725 gr. mercuric oxide, and from the filtrate 0.1714 gr. selenium 

 or 0.2408 gr. selenious acid. 



2) 0.689 gr. salt gave 0.4615 gr. mercuric sulphide or 0.4297 gr. mercu- 

 ric oxide and 0.1564 gr. selenium or 0.2197 gr. selenious acid. 



3) 0.8215 gr. salt did not change its weight, when dried at 100°. 



') Loc. cit. 



