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LXXX. On the Nature of the Forces of Attraction "between 

 Atoms and Molecules. By R. D. KLKEMAN, D.Sc, B.A., 

 McKinnon Student of the Royal Society, Emmanuel College, 

 Cambridge*. 



rilHE surface-tension of liquids illustrates in a striking 

 JL manner the existence of intermolecular forces of attrac- 

 tion. A systematic investigation of the properties of the 

 surface-tension of different liquids would therefore appear 

 likely to lead to the discovery of the exact nature of these 

 forces. The writer "f, working on the same lines as Einstein, 

 has already developed a number of relations connecting 

 surface-tension with other quantities. Since we shall have 

 occasion to refer to them often in this paper they will be 

 placed here for reference. 



■-i-T-n-^oeo' (i) 



k"o 2 



x =^(^.)- 2 (2) 



-^ = H,2<-„ (3) 



r 





T l/2 m 2,3 



~H.Se, 



I 



- pV 



Pi 



or 



= M2c„ 







=B2c. 



...... (4) 



(->) 



(6) 



E denotes the potential energy per unit area and A the 

 surface-tension of the surface of a liquid at the temperature 

 T, and L denotes the internal heat of evaporation, k' , nc", 

 B, H], H 2 , M, denote constants, each of which is the same 

 for all unpolymerized liquids at corresponding states. T 

 p c , p c , denote respectively the critical temperature, density, 

 and pressure of a liquid, Sc a is the sum of a number of con- 

 stants, each of which refers to an atom of a molecule, and is 

 independent of all conditions except the nature of the atom. 

 The values of c a for the different atoms involved were 

 determined in one case by means of equation (6) from data 

 referring to the liquids ether, methyl formate, carbon tetra- 



* Communicated by the Author. 



t Phil. Mag. Oct. 1909, p. 491 ; Dec. 1909, p. 901. 



