Researches on the Salts of Selenious Acid. 



65 



be obtained and the cause of this lies no doubt in the great insolubility of 

 the neutral salt and, on the contrary, the solubility of the tetraselenite in 

 water. If consequently a soluble diselenite is formed for a moment, it is 

 immediately decomposed into insoluble neutral salt and easily soluble te- 

 traselenite. 



It is remarkable that this salt, which contains 2 mol. of water of 

 crystallization, is obtained from the neutral salt with 1 mol. of water, by 

 the addition of free acid. 



Wohler ! ) has examined this salt. He obtained it by the action of 

 selenious acid on metallic zinc. The thus formed selenide of zinc and free 

 selenium being separated and the solution allowed spontaneously to evapo- 

 rate, the compound crystallized in large, yellow, oblique, rhombic prisms, 

 permanent in the air and easily soluble in water; but on heating such a 

 solution decomposition took place, neutral salt separating. 



I have obtained the same salt by treating the neutral selenite 

 Zn.0 2 .SeO t-H 2 with 3 mol. anhydride of acid and water, when solution 

 readily ensued. If this solution, which on heating immediately precipitates 

 waterfree neutral salt, is allowed spontaneously to evaporate, it affords the 

 tetraselenite in large crystals, possessing the appearance and the properties 

 stated by Wohler. 



1) 0.5343 gr. salt gave 0.29 gr. selenium = 0.4075 gr. selenious acid and 

 0.075 gr. oxide of zinc. 



2) 0.507 gr. salt gave 0.2775 gr. selenium = 0.39 gr. selenious acid and 

 0.07 gr. oxide of zinc. 



3) 0.1705 gr. salt lost at 100° 0.0155 gr. of its weight. 



4. Tetraselenite: Zn.0 2 .SeO + 3H 2 .0 2 .SeO. 



Analyses: 



Calculated on 100 parts: 



experiment 



theory 



Oxide of zinc . 

 Selenious acid 

 Water (loss) . 



1. 2. 3. 



. 14.03 13.81 — 



. 76.27 76.92 — 



. 9.70 9-27 9.09 



ZnO 81 13.99 



4Se0 2 444 76.68 

 3H 2 54 9.33 



100.00 100.00 



579 100.00 



') Ann. d. Chemie und Pharni. LXIII. S. 279 (1847). 

 Nova Acta Reg. Soc. Sc. Ups. Ser. III. 



9 



