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LXYI. Molecular Attraction. By J. E. Mills *. 



IN a recent article f on " The Electric Origin of Molecular 

 Attraction/ 7 Mr. W. Sutherland called attention to a 

 relation discovered by the author. Mr. Sutherland's criti- 

 cisms of the author's point of view were largely justified, so 

 far as the papers cited by Mr. Sutherland were concerned. 

 In later papers by the author., overlooked by Mr. Sutherland, 

 the meaning and derivation of the relation were more 

 particularly discussed, and the criticisms made could not, I 

 think, apply to the views there expressed. The author would 

 like therefore to restate the facts and give his own inter- 

 pretation of them. 



I. Statement and Experimental Proof of the Fundamental 

 Equation. 



The relation under discussion can be expressed in the 

 form 



L — Eg 3 _ „ — 



3 n_z /jrj = constant, or \ = /jl ( y/d - '^.D) . (1) 



Here L is the heat of vaporization of one gram of liquid. 

 E e is the energy spent in overcoming the external pressure 

 as the liquid vaporizes and expands from the density of the 

 liquid d, to the density of the vapour D. L— E e is, there- 

 fore, equal to the internal heat of vaporization and is 

 designated X. The constant given by the equation is called 

 ///. It is a characteristic constant for any liquid and is not 

 affected by changes in temperature. 



The above equation has been tested for thirty-eight 

 substances t, and a summary of the results obtained is given 

 in the last two papers referred to above. 



I think that the evidence there presented is sufficient to 

 justify the conclusion that the equation 



L-E e 

 3-—— § — = constant 

 vd— \/\J 



represents a new and most exact law, holding true at all 

 temperatures for a'l normal non-associated liquids. 



* Communicated by the Author. 



t Phil. Mag. [6] vol. xvii. p. 664 (1909). 



t Journ. Phys. Chem. Part I. vol. vi. p. 209 (1902); Part II. 

 vol. viii. p. 383 (1904); Part III. vol. viii. p. 593(1904); Part IV. 

 vol. ix. p. 402 (1905); Part V. vol. x. p. 1 (1906); Part VI. vol. xi. 

 p. 132 (1907); PartVIl. vol. xi. p. 594 (1907); Part VIII. vol. xiii. 

 p. 512 (1909). Journ. Amer. Chem. Soc. vol. xxxi. p. 1099 (1909). 



