SELENIUM, 



salt then amounted to 4 '856 grains ; this subtract- 

 ed from 32*666 leaves 27*816 grains of biseleniate 

 of soda. Now, it contains 21 -63 grains of selenic 

 acid. Hence, biseleniate of soda is composed of 



Selenic acid 21-63 or 14> 

 Soda 6-18 - 4 



27-61 



This experiment gave therefore 7 for the atomic 

 weight of selenic acid. But I consider this as 

 merely an accidental circumstance, because, on 

 repeating it a second time, the biseleniate was 

 found a compound of 



Selenic acid 12-353 

 Soda 4 



This would reduce the atomic weight of selenic 

 acid to 6'176. But this mode of experimenting 

 is not susceptible of the requisite degree of pre- 

 cision for deciding so delicate a point. Every 

 time the salt was evaporated to dryness, a little 

 selenium was separated, which prevented the 

 quantity of salt from remaining quite perma- 

 nent. 



I attempted to determine the atomic weight 

 of selenic acid, by precipitating it from seleniate 

 of soda, by means of muriate of barytes. But 

 the precipitation produced by this salt is only 

 partial a portion of selenic acid remaining in 

 solution even after a considerable excess of 

 muriate of barytes had been added. 



VOL. I. P 



