578 Dr. R. D. Klceman on Molecular Attraction 



From thermodynamics and the law of attraction we obtain 



T = w(^) il3 (% VmO 2 , (5) 



where H 2 has the same value for all liquids at corresponding 

 temperatures *. At the critical point the equation becomes 



( n \4/3 , . TJ 2/ n \4/3 



ft) (V^=$,® (W»,r, 



and therefore 

 and 



TT2 n zi*-c 



Equation (5) was proved for low temperatures, but it will be 

 easily seen that if it holds for one corresponding temperature 

 of: a number of liquids it will hold for all temperatures, and 

 the value of H 2 is that given above. 



From thermodynamics and the law of attraction we also 

 have 



P = M2 (.n) 7 ' 3(2 ^ )2 ' * • • • (G) 



where M 2 is the same for all liquids at corresponding tem- 

 peratures f. At the critical temperature this equation 

 becomes 



and therefore 



n,M c 2 



M 9 = 



v /3 



The values of the quantities w 1? n 2 , n 3 and ?? 4 , in the above 

 equations, may be expressed in terms of one of them along 

 the lines indicated in a previous paper J and in this paper. 



The Laiv of Attraction between Molecules stated in 



a more General Form. 



The law of attraction given at the beginning of the paper 



we would expect on account of its generality to represent the 



facts only approximately in some cases. We have seen in 



* Phil. Mag. Oct. 1909, p. 509 ; and May 1910, p. 787. 

 t Phil. Mag. Dec. 1909, p. 903 ; and May 1910. p. 788. 

 X Phil. Mag. March 1911, p. 325. 



