﻿THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



JULY 1894. 



I. The Attraction of Unlike Molecules. — I. The Diffusion of 

 Gases. By William Sutherland*. 



IN my previous papers on the laws of molecular force the 

 attractions of like molecules have heen under considera- 

 tion, and the results seemed to indicate that the laws of 

 the attractions of unlike molecules would not be difficult to 

 ascertain. With the hope of determining the general law of 

 attraction of any two molecules, I adopted two methods as 

 being at present available for giving values of the attrac- 

 tions of unlike molecules, namely, that of the Diffusion of 

 Gases and that of the Surface-Ten sion of Mixed Liquids. 

 Both methods have led to the same result, viz., that if the 

 attraction between two molecules M t of mass m l at distance r 

 apart be denoted by SAim^/r 4 , and that between two molecules 

 M 2 by 3A 2 ?7? 2 2 /r 4 , then the attraction between an M 1 and an M 2 is 



3 \/A 1 A 2 m 1 m 2 /r 4: j 



or the attraction of two unlike molecules is equal to the 

 square root of the product of the attractions of the corre- 

 sponding like molecules at the same distance apart. As the 

 expression SA^i^ for two like molecules can be split into 

 two parts V3A 1 ?n l , the general law of the attraction of any 

 two molecules, like or unlike, can be stated thus : — Any two 

 molecules attract one another with a force inversely pro- 

 portional to the fourth power of the distance between them 



* Communicated by the Author. 

 Phil. Mag. S, 5. Vol. 38. Nq. 230. July 1894. B 



