14 



Dr. E. P. Perinan and G. A. S. Atkinson. 



during the whole of the experiments. With this arrangement one 

 scale division was equivalent to about 2° C. The porcelain tube con- 

 taining the couple was supported by asbestos some distance above the 

 floor of the muffle. The variation of temperature between the floor 

 and the top of the muffle was found to be 6° C. at a temperature of 

 about 600" C, and 8° C. at 900° C. ; no correction was made for this 

 difference as the couple was near the level of the centre of the globe. 



Between the two fixed points obtained the scale reading was taken 

 to be proportional to the difference of temperature, according to the 

 method used by Roberts- Austen. 



Determination of Pressure. — The pressure was read off on a standard 

 barometer, or on the pressure gauge G in the case of pressures less 

 than atmospheric. 



Capacity of the Globe. — The porcelain globe was weighed full of air, 

 and again weighed, filled with water, and the capacity calculated. The 

 filling with water was effected by repeated exhaustion and letting in 

 water. 



Preparation of Pure Bromine. — Commercial bromine was purified by 

 one of the processes previously employed, viz., by boiling with potas- 

 sium bromide, distilling over red-hot manganese dioxide, shaking with 

 strong sulphuric acid, and re-distilling. The greater portion came over 

 at a perfectly constant temperature, 58'9° C. at a pressure of 761 mm. 

 {Cf. former paper.) 



Eesults. 

 Series I. About 650° C. 





Volume 







Vapour- 



Weight of Br. 



of globe. 



Pressure. 



Temperature. 



density. 



grammes. 



c.c. 



mm. 







0-6076 



294-3 



765-5 



677-5° 



79-3 



0-6348 



294-3 



765-5 



650-0 



80-4 



0-6013 



275-1 



758-0 



631-0 



80-4 









Mean 



80-0 





Series II. 



About 



830° C. 





0-4914 



276-0 



758-0 



828-0° 



79-7 



0-4656 



276-0 



758-0 



873-0 



78-6 



0-4850 



276-0 



758-0 



833-0 



79-0 



0-4896 



276-0 



758-0 



830-0 



79-6 



1-9380 



1052-0 



767-0 



799-0 



79-6 



0-5335 



295-1 



765-0 



833-0 



80-6 



0-5371 



295-1 



765-0 



820-0 



80-1 



0-5244 



295-1 



765-0 



845-0 



80-0 



Mean 79-7 



