1890.] 



Experiments on Vapour-density. 



49 



Series II. Temperature, 78'4. 



The only noticeable point in this series is the highness of the last 

 vapour-density at the lowest pressure. 



A single experiment was then made in order to try the effect of 

 continued heating on bromine vapour at a low pressure. After three 

 hours' heating at 78'0 and 15*35 mm. pressure, the vapour-density 

 came out abnormally high, viz., 92*6. Professor J. J. Thomson found 

 vapour-densities 66'5 and 70 at much higher pressures and somewhat 

 higher temperatures than these. 



Series III. Temperature, 155'5 (Bromobenzene) ; Capacity of 

 Globe, 447-1 c.c. 



Here there is still no sign of dissociation, and what seems some- 

 what remarkable, even at low pressures the vapour-density is above 

 the normal density. 



The pure bromine being then exhausted, a fresh sample was pre- 

 pared from the residues and from some commercial bromine treated 

 with potash ; the whole was evaporated to dryness, ignited, distilled 

 with sulphuric acid and potassium bichromate, and dried by shaking 

 with sulphuric acid, allowing to stand, and re-distilling ; the greater 

 portion came over at o8'9 (corrected to 760 mm.), it commenced to 

 boil at 58 0- 55, but the boiling point soon rose to 58"9, and then 

 remained constant. 



A determination was then made of the density of bromine vapour 

 as nearly as possible saturated at 15. The globe was immersed in 



VOL. XLVTII. K 



