574 Dr. R. D. Kleeman on Molecular Attraction 



Substituting for p from this equation in equation (2) we 

 obtain 



c (V^g) 7/3 .^(|)=T(f-o-i). 



It will be seen that the right-hand side of this equation must 



T 



be a function of the ratio ^-, and we therefore have that 



B = aT c , where a and C are universal constants. Further, 

 e A contains the factor T°, and therefore 



The vapour pressure equation then becomes 



log^log^S^) 2 (£)"*)- ^ - C log T. 



The corresponding equation for the internal heat of 

 evaporation is 



HH><^>tnf) v ^- c -'). 



By equating two different formulae for the internal heat 

 of evaporation we obtain a relation between the quantities 

 T, T c , p u p 2i and p c . We have already given examples of 

 this in a previous paper. Since the equation for the heat 

 of evaporation may within certain restrictions be given any 

 form we please, this applies also to the equations obtained 

 in the above way. An example which is of interest will be 

 given in this paper. Let us put 





in the general equation for the heat of evaporation, and we 

 obtain 



L=(p 1 -, 2 > 2 (l + ^ + f 2+ ...)i^ 



\ 2 n 1/3 

 Wj ) Pc ' 



,7/3 > 



where c 2 is a numerical constant. An equation for the heat 

 of evaporation which we have already established * is 



where c 3 is a numerical constant. Equating these two 

 * Phil. Mag. Oct. 1010, p. 678. 



