Researches on the Salts of Selenious Acid. 



19 



Calculated on 100 parts: 



found 



theory 



1. 2. 



Oxide of caesium . . 35.64 35.88 

 Selenious acid. ... 55.94 56.66 

 Water (loss) 8.42 7.46 



V 2 Cs 2 141 36.15 

 2Se0 2 222 56.92 

 iy 2 H 2 27 6.93 



100.00 100.00 



390 100.00 



SELENITES OF AMMONIUM. 



i. Neutral: Am 2 .0 2 .SeO + H 2 0. 



If the strongest caustic ammonia be added to anhydride of selenious 

 acid, a lively combination takes place under eftervescence and evolving of 

 great heat. Particles of selenium are then sometimes separated, probably 

 owing to the strength of the heat and the decomposition between ammonia 

 and selenious acid, which, as Berzelius has shown, cannot consist together 

 at a higher temperature. A solution thus prepared and still containing 

 ammonia in great excess, when allowed to evaporate to strong concentration 

 over sulphuric acid, affords a salt in well developed, large crystals; this is 

 not, however, a neutral salt, but a sesquiselenite, as will be soon shown. 

 Berzelius' supposition that a neutral salt is obtained in this manner, does 

 not therefore hold good; it seems also to have been pronounced withoui 

 any previous analyses. 



On the contrary, if selenious anhydride be dissolved in alcohol, in 

 which it is very soluble, and ammonia-gas passed into the solution, this is 

 considerably heated and, when nearly saturated with gas, affords the neutral 

 salt so speedily that the gas-delivery-tube is very liable to be obstructed 

 by it. The salt is thus obtained in small, acicular, milk-white crystals, 

 united in bundles, and, for reasons easily intelligible from what follows, 

 must be speedily desiccated and weighed in a closely covered vessel, in 

 order to obtain it in a state fit for analysis. Ammonia-determinations on 

 this and following compounds are made by heating tlie salt with soda-lye, 

 passing the gas into hydrochloric acid, evaporating the solution at 100° 

 and weighing the remaining sal-ammoniac. 



