Researches on the Salts of Selenious Acid. 



45 



3. Triselenite: Mg.0 2 .Se04- 2H 2 .0 2 Se04-3H 2 0. 



This salt crystallizes also slowly from a solution, containing 3 mol. 

 selenious acid to 1 mol. neutral selenite, and not before this is so concen- 

 trated, that the vessel may be turned upside down, without its running out. 

 The crystals were formed by small, shining prisms of a rhombic appearance, 

 with the acuter edges cut by slightly developed brachydiagonal end-faces 

 and the ends of basal end-faces. 



Analyses: 



1) 0.4612 gr. salt gave 0.2343 gr. selenium or 0.3292 gr. selenious acid 

 and 0.04 gr. magnesia. 



2) 0.44G6 gr. salt gave 0.2308 gr. selenium or 0.3243 gr. selenious acid 

 and 0.0385 gr. magnesia. 



Calculated on 100 parts: 



experiment theory 



1. 2. 



Magnesia 8.67 8.62 MgO 40 8.64 



Selenious acid . . 71.39 72.61 3Se0 2 333 71.92 



Water (loss) . . . 19.94 18 77 5H 2 90 19.44 



TooToo 100.00 "463 100.00 



The extraordinary degree of saturation of this salt, not observed 

 before for selenious acid, induced me to repeat the experiment, then allowing 

 the crystallization to take place at 60°. Now there was obtained another 



4. Triselenite: Mg.0 2 .SeO + 2H 2 .0 2 .SeO. 



free from water of crystallization. It crystallized from a syrupy solution 

 in lentil-formed aggregates of crystals; probably the individual crystals were 

 formed by rhombic lamels. In cold water, this salt dissolves pretty slowly. 



An aly ses: 



1) 0.5645 gr. salt gave 0.3295 gr. selenium or 0.463 gr. selenious acid and 

 0.1875 gr. sulphate of magnesium or 0.0625 gr. magnesia. 



2) O.533 gr. salt gave O.3117 gr. selenium or O.4379 gr. selenious acid and 

 0.177 gr. sulphate of magnesium or 0.059 gr. magnesia. 



