76 



L. F. Nilson, 



mercuric oxide and the solution from which the neutral salt had commenced 

 to separate, evaporated. It crystallizes in large, rifled, prismatic crystals, 

 containing- a considerable quantity of crystallization-water, and is to a very 

 slight extent soluble in alcohol. Potash does not completely precipitate the 

 mercuric oxide; the salt of potassium must therefore be heated in order to 

 be liberated from mercury. On heating, it fuses and sublimes unaltered. 

 With sulphurous acid white mercurous selenite is first precipitated, then 

 pink selenium." 



With the selenites ot mercury, the account of the salts of the biva- 

 lent metals with selenious acid is at an end. Within this class, calcium, 

 strontium, barium seem to form a natural group, characterized by its ina- 

 bility to yield salts more acid than diselenites with excess of selenious 

 acid. Their diselenites appear to be easily converted into anhydrous salts, 

 and these are the only salts known of barium and lead. The extraordinary 

 amount of water in the neutral selenites of calcium and strontium may 

 also be worth notice. 



Within the other group of the bivalent metals, manganese and cop- 

 per approach the above, in as much as that they do not form salts more 

 acid than diselenites, both of them anhydrous salts. Among the neutral 

 selenites belonging to this group, there is to be found a remarkably great 

 number with 2 mol. water of crystallization: 



Be.0 2 .SeO + 2H 2 

 Mn.OlSeOf 2H 2 

 Co.0 2 .SeO -f 2H 2 

 Ni.0 2 .SeO+2H 2 

 Cu.0 2 .SeO + 2H 2 

 Zn.0 2 .SeO + 2H 2 0. 



Magnesium, cobalt and glucinum exhibit a remarkable phenomenon, 

 when treated with 4 mol. selenious acid, triselenites being formed instead 

 of tetraselenites; as these salts have been formed under precisely the same 

 circumstances, the solutions containing 1 mol. of the base to 4 mol. of the 

 acid, at the same temperature and by a similar treatment in other respects; 

 they are, as already observed, very interesting with regard to the compo- 

 sition of glucina or the qvantivalence of glucinum, and seem to form a not 

 unimportant addition to the evidences, before communicated, for the biva- 

 lence of glucinum. Also the diselenite and the neutral salt of glucinum are 



