30 



L. F. Nilson, 



2) 0.832 gr. salt gave 0.4712 gr. selenium or 0.6621 gr. selenious acid and 

 0.2103 gr. sulphate of sodium or 0.0918 gr. soda. 



3) 0.5358 gr. salt, being kept over sulphuric acid, exhibited no change of 

 weight; at 100°, it fused down to a tough, viscid mass and then, after 

 long heating, lost 0.035 gr. 



theory 



y 2 Na 2 31 11.07 

 2Se0 2 222 79.28 



iy 2 H 2 27 9.65 



280 100.00 



At 100°, the salt lost 2 / 3 of its hydrogen, one half very speedily, 

 the other much more slowly. It seems probable that here, as was also the 

 case with the tetraselenite of potassium, an anhydrous salt of the composi- 

 tion NaH.0 2 .SeO -j- SeO 2 remains as a mass, viscid when warm, glassy when 

 cold, and, owing to reducing gases, slightly redcoloured by traces of se- 

 parated selenium. 



The foregoing analyses show that this salt contains no water of 

 crystallization. Muspratt is of another opinion, on the strength of two 

 soda determinations — 11.56 and 12.41 pr. ct. — which in his numbers, 

 have been erroneously set down as amount of water. In other respects, 

 these determinations agree better with the composition of the waterfree salt, 

 than with the formula Na 2 O.Se0 2 + 3H 2 O.Se0 2 + H 2 0, assumed by him. The 

 material he employed for the analysis is so much more surely identical with 

 the salt described above, as it was previously dried over sulphuric acid. 



As magnesium, glucinum and cobalt have given salts in a stage of 

 saturation between diselenite and tetraselenite, I made an experiment with 

 sodium that proved that no triselenite exists of this metal. A solution, 

 obtained by treating one mol. carbonate of sodium with three mol. selenious 

 anhydride, yielded namely, on spontaneous evaporation, a salt in oblique, 

 four-sided prisms, with ortho- and klino-diagonal end-faces and several com- 

 bination-faces at the ends. After recrystallization from water, 



0.5168 gr. salt, fumed with sulphuric acid, gave 0.129 gr. sulphate 

 of sodium or 0.0563 gr. soda; in 100 parts: 10.90, a value that proves the 

 compound to be a tetraselenite. 



Calculated on 100 parts: 



experiment 



1. 2. 3. 



Soda 10.93 11.04 — 



Selenious acid. . . 78.57 79.58 — 



Water (loss) . . . 10.50 9.38 6.53 



loo.oo loo. 00 



