MOLECULAR ATTRACTION, IV., ON BIOT'S FORM- 



ULA FOR VAPOR PRESSURE AND SOME 



RELATIONS AT THE CRITICAL 



TEMPERATURE. 1 



J. E. MILLS. 



SP 



THE y~r OF A LIQUID. 



In a preceding paper 2 we examined the following- equation, 

 which had been proposed on theoretical grounds by Mr. H. 

 Crompton, 



[1] L = 2J V* = 2RTlog e A = 9 J|i Tl0 g.^. cals . 



(L is heat of vaporization, v and V denote volume of liquid 

 and vapor, d and D the density of liquid and vapor, p is pres- 

 sure, T is temperature, m is molecular weight, R is the con- 

 stant of the gas equation, PV = RT.) 



It was there shown that this equation gives at low temper- 

 atures where the pressure is small, results for the heat of 

 vaporization that are invariably and usually very considerably 

 too large. But at the higher temperatures examined, that is 

 as the critical temperature is approached, the results given 

 by the equation appeared to be correct. The evidence there 

 given as to the correctness of this equation at high tempera- 

 tures was very considerable and justified further use of the 

 equation. Therefore in this paper we combined the usual 

 thermodynamical equation for calculation of the heat of 

 vaporization, 



1 Reprinted, with omission of a Table, from Jour. Phys. Chem., 9, p. 402, 

 1905. 



2 Jour. Phys. Uhem. 8, 593 (1904). 



88 [June 



