34 



L. F. Nilson, 



tallic silver remains. Berzelius from whom these statements are for the 

 most part taken, found by analysis that the salt had the above composition. 



In accordance with Thomsen's *) project, selenite of silver has been 

 employed to procure selenic acid, and this method, depending upon the 

 action of moist bromine on this salt, makes it now an easy task to obtain 

 this acid in a pure state which, by the methods formerly known, was 

 attended with much difficulty. 



With this salt, the description of the selenites of the monatomic me- 

 tals is at an end. They show a striking analogy, one to another, as to 

 constitution and properties. All, except silver, have afforded, besides neutral 

 salts, also diselenites and tetraselenites; the latter are all composed accor- 

 ding to the formulae: 



RH.0 2 .SeO and 

 RH.0 2 .SeO + H 2 .0 2 .SeO. 



The compounds are easily soluble in water, except selenite of silver, 

 which dissolves but to an inconsiderable amount; the neutral salts of thal- 

 lium and lithium are rather difficult to be dissolved, as compared with the 

 others, that most often deliquesce. As usual, there is to be observed a 

 closer agreement of properties in the salts, if the metals in question be 

 arranged in two groups, with potassium and sodium as types. Thus, for 

 instance, all neutral salts of the potassium-group 2 ) are composed according 

 to the formula 



R 2 .0 2 .SeO + H 2 0. 



and all deliquesce, on exposure to the air; this is also the case with the 

 diselenites. The diselenites as well as the neutral salts of the sodium-group 

 are on the contrary permanent in the air. 



Now follows to pass to the compounds of the diatomic metals with 

 selenious acid. 



Tidskrift for Physik og Chemie Bd 8 s. 286. 

 2 ) Except csesiumselenite with 3 mol. water. 



