5fi6 Dr. R. D. Kleeman on Molecular Attraction 



the bulb with an exhausted chamber. Dust-free air from A 

 was then admitted, and the air remaining in EF driven along 

 into the cloud- chamber in the way already described. No 

 cloud, not even a shower, was obtained on expanding, showing 

 that the fall of pressure in the bulbs had not liberated nuclei 

 from the P 2 5 . Thus the nuclei on which the coloured cloud 

 was subsequently obtained must have been the result of the 

 cooling process through which the air had passed. 



Conclusion. 



The experiment shows that if dust-free air, dried by 

 standing for three weeks over phosphorus pentoxide, be 

 cooled to a very low temperature, such as that of liquid air, 

 large numbers of small invisible nuclei are produced in the 

 gas. It is difficult, however, to decide with absolute certainty 

 whether these particles are aggregations of ivater-molecules 

 or of azV-molecules. Owen and Hughes, in their original 

 papers, were led to suggest the latter, that is, the air-molecule, 

 hvpothesis. The result of the experiment described in the 

 present note supports that view. 



Holt Physics Laboratory, 

 University of Liverpool, 

 April 7, 1911. 



LIV. Molecular Attraction and the Properties of Liquids. 

 By R. D. Kleeman, D.Sc, B.A., Mackinnon Student of 

 the Royal Society, and Clerk Maxwell Student of the 

 University of Cambridge *. 



IN a previous paper the writer has shown that an infinite 

 number of equations can be obtained connecting the 

 internal heat of evaporation or surface tension of a liquid 

 with its temperature, density, and density of the saturated 

 vapour t- These equations can be deduced by means of the 

 law of attraction between molecules obtained from the 

 surface tension of liquids on giving the arbitrary function 

 in the law various appropriate forms. On equating the 

 various expressions obtained for the surface tension or 

 latent heat, useful equations equations connecting the other 

 quantities relating to a liquid may be obtained J. Examples 

 of the foregoing results are given in the papers quoted. The 

 subject will be further developed in this paper. 



* Communicated bv the Author. 

 t Phil. Mag. Jan. i911, pp. 83-102. 

 \ Phil. Mag. March 1911, p. 352. 



