408 Prof. It. Weber on a new Oxide of Sulphur. 





Selenium-E stimation 





Substance 

 taken. 



Selenium. 



Selenium 

 per cent. 



1*428 



0-695 



48-67 



0-930 



0-455 



48-87 



0-682 



0-332 



48-68 



1-855 



0-926 



48-43 



1-230 



0-609 



49-51 





Mean . . . 



49-03 





Sulphur-Estimation. 





Substance 



Barium 



Sulphur 



taken. 



Sulphate. 



per cent. 



1-120 



1-581 



19-40 



0-916 



1-327 



19-91 



0-940 



1-333 



19-49 



0-839 



1-225 



20-06 



Mean . . . 19'71 

 The composition of this substance may be expressed by the 

 empirical formula SeS0 3 , which requires 



Selenium . . 49*68 per cent. 

 Sulphur. . . 20-12 „ 

 This body is therefore a compound analogous to dithionic 

 oxide, in which one atom of sulphur is replaced by one atom 

 of selenium. These compounds are produced by the imme- 

 diate addition of one atom of sulphur, or of selenium, to sul- 

 phuric anhydride. 



The products obtained from each by decomposing them 

 with water show that the collocation of the atoms is the same 

 in each. In both cases the chief product is sulphuric acid, 

 accompanied by sulphurous acid ; in the decomposition of the 

 selenium compound selenious acid is also produced; and in the 

 decomposition of the sulphur compound, hyposulphurous acid 

 or one of the polythionic acids is formed. The largest por- 

 tions of the elements, sulphur or selenium, are separated as 

 such on the addition of water. The constitution of this sub- 

 stance can only be guessed at, inasmuch as it has not been 

 possible to obtain compounds derived from it. 



Although ammonia reacts with this compound with the 

 production of a brown-red substance, yet, on account of the 

 energy of the reaction (notwithstanding that the containing 

 vessel was carefully cooled), it has not been possible to obtain 

 this substance in a definite form. 



Behaviour towards Sulphuric Acid. 

 The selenium compound is insoluble in excess of pure sul- 

 phuric anhydride; but it is dissolved by anhydride containing 

 hydrate ; with the formation of an intensely green liquid, from I 



