igof\ Mills — Molecular Attraction. 89 



T fiP 8 P 



[2] t = -j- (V - v)~ = .0 4 31833 T (V - v^ cals. 



with the equation of Crompton given above, and obtained 

 equation 15 of that paper, viz. : 



1 JV 

 8P __ 287500 Qg y 

 LJ 8T~~ w V-* 



We there showed that the limit approached by this equation 

 as the critical temperature was approached and V approached 

 v in value, was, 

 r .. ^P __ 124860 



We at that time overlooked the fact that this equation 4 

 could be expressed in the very simple form, 



[51 iP_lR 



Here V is the critical volume and R is the usual g-as constant, 



and we have the striking- conclusion that at the critical tem- 



8 P 

 ferature the y= of the liquid {vapor) is exactly twice -what it 



would be for that substance as a perfect gas occupying the same 

 volume. Expressed in this form the bearing of equation 3, or 

 its limiting forms, on the kinetic relations of a liquid and its 

 vapor, assumes more importance and justifies a closer study. 

 Accordingly by means of equation 4, we calculated, and 



SP 

 give in Table 1, the values of the -^~ at the critical temper- 

 ature for twenty substances. The critical data used is that 

 given by Dr. Young 1 . This data is more correct than that 

 given in earlier papers. (We would here note that in the third 

 paper on Molecular Attraction 2 we overlooked this corrected 

 data, but have since repeated the calculations there given 



iPhil. Mag., [5], 50, 291 (1900). 

 3 Jour. Phys. Ohem., 8, 593, (1904). 



