Prof. R» Weber on a new Oxide of Sulphur. 399 



follow up this observation, but contented himself with showing 

 that the liquid fumed strongly in the air, smelt of sulphurous 

 acid, and was decomposed by water with precipitation of 

 sulphur. 



F. C. Vogel *, who is usually regarded as the discoverer of 

 this blue-coloured substance, was aware of the observation of 

 Bucholz. 



In 1812 this chemist prepared a blue substance by the 

 action of sulphur upon sulphuric anhydride, which he had 

 obtained by heating fuming oil of vitriol ; at the same time 

 he obtained a green and also a brown-coloured liquid, accord- 

 ing as he added smaller or larger quantities of sulphur to the 

 anhydride. Vogel looked on these bodies as compounds of the 

 anhydride with varying proportions of sulphur ; the blue 

 compound he supposed to contain the smallest, and the brown 

 the largest quantity of sulphur. 



In repeating the experiments of Vogel, Schweigger f 

 observed that the blue compound, obtained by the action of 

 the vapours of heated oil of vitriol upon sulphur, which was 

 contained in a receiver luted to the retort, gradually became 

 green in colour, then brown, and was finally converted into 

 ordinary yellow sulphur. 



BerzeliusJ, who formed his opinion as to the nature of this 

 substance after Schweigger's observations were known, con- 

 sidered that the blue liquid contained sulphur dissolved in, but 

 not combined with the acid, and that the substance obtained 

 by the action of sulphuric anhydride upon sulphur was not an 

 oxide of sulphur. 



Wach § sought to determine the relative quantities of sul- 

 phur and of anhydride in the differently coloured compounds 

 by heating weighed quantities of the constituents in sealed 

 tubes, and observing the colours of the products. The brown 

 compound was produced from a mixture of one part of sulphur 

 with five of anhydride ; the blue, from one part of sulphur 

 with ten of anhydride. Inasmuch as Wach did not separate 

 the substances which he obtained from excess of the materials 

 used, we cannot suppose that he was really dealing with pure 

 compounds ; on distilling the coloured bodies he obtained a 

 brown oily liquid which appeared to be ordinary oil of vitriol. 

 Wach's results therefore give no answer to the question con- 

 cerning the composition of these substances. 



* Schweigger's J. fur Chemie u. Physik, vol. iv. p. 121. 

 f J. fur C7iem. u. Physik, vol. xiii. p. 484. 

 % Lehrbuch, vol. i. p. 485 (5th edit.). 

 § Schweigger's Journal, vol. 1. p. 1. 



