The constitution of sulphur vapour

Abstract

The constitution of sulphur vapour has been studied by many investigators, the method usually employed being based upon the determination of the density. In 1835 Dumas and Mitscherlich found the vapour density at temperatures near the boiling point to be 6∙56, which corresponds closely with the molecular formula S 6 . Deville and Troost carried out determinations at temperatures ranging from 860°C to 1040°C. and obtained the value 2∙23 which is that required by the formula S 2 . More recently Biltz has shown that below 800°C. the density is greater than is required by the formula S 2 , and at 468°C. becomes 7∙8 which corresponds approximately to the formula S 7 , without any constant value being observed between these temperatures. Bleier and Kohn found that when determinations were made under reduced pressure between 192°C. and 310°C. the density of the vapour gradually rose with increase of pressure and slowly but asymptotically approached the value S 8 . Evidence of the existence of molecules containing eight atoms has also been obtained from an examination of solutions of sulphur. Biltz holds that the value obtained by Dumas and Mitscherlich is only of significance for the conditions of temperature and pressure under which it was determined, and affords no evidence of the presence of hexatomic molecules in the vapour. His view is that only octatomic and diatomic molecules have any existence, the former gradually dissociating into the latter as the temperature is raised until about 900° C., the dissociation of the heavier molecules is complete and the vapour is composed entirely of diatomic molecules. Above this temperature no further change appears to occur. Premier, on the other hand, from a study of the curve representing the change of density with change of pressure considers that it is not unlikely that hexatomic and tetratomic molecules are formed as intermediate pro­ducts of the dissociation of the octatomic molecules. Of this, however, the investigation of the vapour density does not afford any conclusive evidence.