162 Journal of the Mitchell Society. [Dec. 



no 



?50° 



50° 150° 200° 



Diagram 8. 

 Ordinates give internal heat of vaporization in calories. 



have given its value for each substance and temperature 

 examined. (See second paper, Tables 2 to 22, under head- 

 ing- Ej. 



E 



It has been sug-g-ested that ~- is a constant, 



SP 



Since E is 



0.0 31833 P (V — v) and L = 0.0 31833 T -^^ (V — v), this 



F 8 P 



would require that -—- = PT -^r = constant. This relation 



lv 1 



is not confirmed. Examination shows that E x first increases 

 and then decreases with the temperature, while the latent 

 heat, almost invariably, decreases. E T thus varies independ- 

 ently of the latent heat and rang-es usually between seven 

 and fourteen per cent, of its value. 



It was therefore thought best to subtract from the total 



