Researches on the Salts of Selenious Acid. 



23 



The analogy between the selenites, now analyzed, and the correspon- 

 ding carbonates is obvious. As one of the several products of decomposi- 

 tion, a sesquiselenite appears here, corresponding to the sesquicarbonate of 

 ammonium, frequently met with in commerce. 



4. Tetraselenite: AmH.0 2 .SeO + H 2 .0 2 .SeO. 



From a solution, obtained by treating the neutral selenite of ammo- 

 nium with precisely three molecules of selenious anhydride or 184 p. ct, 

 the tetraselenite crystallized over sulphuric acid under the receiver of the 

 airpump, only with great difficulty, however, the crystals being so deli- 

 quescent, that it is hardly possible to ascertain their form under the mi- 

 croscope, before they have liquefied at the edges. The salt forms large, 

 long, four-sided prisms, with oblique end-faces. It was analyzed after long 

 keeping over sulphuric acid, when there remained a white, opake salt-mass. 



Analyses: 



1) 0.822 gr. salt gave 0.1415 gr. sal-ammoniac or 0.0688 gr. oxide of am- 

 monium. 



2) 0.7555 gr. salt gave 0.128 gr. sal-ammoniac or 0.0622 gr. oxide of 

 ammonium. 



3) 0.5465 gr. salt gave 0.3415 gr. selenium or 0.4798 gr. selenious an- 

 hydride. 



4) 0.556 gr. salt gave 0.347 gr. selenium or 0.4875 gr. selenious an- 

 hydride. 



In 100 parts: 



1. 2. 3. 4. 



Oxide of ammonium 8.37 8.23 ■ — — 



Selenious acid — — 87.80 87.69 



These values, it is true, do not agree with the formula above, 

 AmH.OlSeO + H'.0 2 .SeO, which requires 



V 2 Am 2 26 9.45 

 2Se0 2 222 80.73 

 iy 2 H 2 27 9.82 

 275 100. oo; 



but it is hardly doubtful that the obtained, highly deliquescent salt has this 

 composition, in analogy to all tetraselenites of the monatomic metals. The 



