A. W. Peirce — Existence of Selenium Monoxide. 165 



dioxide, prepared as described in previous articles, and precip- 

 itated in some cases with sulphurous acid, in some instances 

 with potassium iodide, dried to a constant weight at 100° and 

 then heated to the temperature and for the periods indicated 

 below : 





Se found 











xp. 



at 100°. 



Temp. 



Time. Weight. 



Loss. 





grm. 







grm. 



grm. 



1. 



0-0356 



110° 



iho 



ur 0-0350 



0-0006 







130° 



\ ' 



' 0-0348 



0-0002 



2. 



0-0355 



110° 



h ' 



' 0-0350 



0-0005 







130° 



i ' 



0-0347 



0-0003 







150° 



i ' 



0-0346 



00001 



3. 



0-0576 



180° 



8i ' 



' 0-0546 



0-0030 



4. 



0-0576 



180° 



8i ' 



' 0-0558 



0-0018 



5. 



0-3324 



180° 



2 * 



0-3306 



0-0018 



6. 



0-3500 



180° 



li ' 



0-3445 



0-0055 



Y. 



0-4274 



180^ 



H ' 



0-4232 



0-0042 



Other experiments were made for the purpose of deter- 

 mining if possible just how the losses occur. The selenium 

 collected as usual upon asbestos in a perforated crucible was 

 introduced into a large glass tube placed horizontally in an air 

 bath in such manner that the tube extended outside the bath 

 at both sides and remained cool at the ends. A current of dry 

 air was drawn through ignited asbestos and then through the 

 tube containing the selenium and crucible, and passed to the 

 suction pump through a glass trap filled with water. A ther- 

 mometer placed within the tube and closely adjacent to the 

 selenium showed the temperature of the selenium as the 

 experiment progressed. On gradually heating the bath no 

 change was observed at first, but at 180° C. a mirror of red 

 elementary selenium formed on the cooler portions of the tube 

 outside the bath, but did not extend so far as the trap. At the 

 end of the heating the crucible was weighed and the loss 

 determined. The washings of the tube and the trap when 

 acidified and tested with potassium iodide gave no indication 

 of selenious acid, as would inevitably be the case if selenium 

 dioxide were formed and volatilized during the heating. The 

 loss is due, therefore, entirely to the volatilization of the 

 selenium as such. 



Se found 



Exp. 



at 100°. 



Temp. 



Time. 



Weight. 



Loss. 



8. 



0-0706 



180° 



2i 



hours 



0-0628 



0-0078 



9. 



0-0987 



180° 



1| 



(( 



0-0948 



0-0039* 



10. 



0-3192 



180° 



4 



a 



0-3121 



0.0071 



11. 



0-0983 



180° 



3f 



i( 



0-0925 



0-0049 







200° 



2 



a 



0-0876 



0-0058 



* In current of COo instead of air. 



