THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAlC^A&iLZINE 



fD MAY 13 1 92 < 

 JOURNAL O^SCIENC 



[SIXTH SERIES.] 



MA Y 1922. 



XCI. Notes on the Kinetic Theory of Gases. Sutherland' 's 

 constant S and van der Waals 9 a and their relations to 

 the inter 'molecular field. By R. H. Fowler, Fellow and 

 Lecturer of Trinity College, Cambridge *. 



§ (1). Introduction and Summary. — This paper consists o£ 

 two somewhat loosely connected parts. In the first part, 

 § 2, I point out the conditions under which a strict com- 

 parison may be made between the intermolecular fields 

 deduced from Sutherland's constant S and from van der 

 Waals' a. On comparing the numerical results I have then 

 to point out a serious outstanding discrepancy between the 

 values deduced in these two ways ; I make a suggestion as 

 to the probable source of this discrepancy, but have not yet 

 resolved it in detail. 



In the second part, §§ 3-11, I give two simple proofs of 

 the exact formula for van der Waals' a as a function of the 

 intermolecular field of force which I believe to be illuminating 

 and new, or at least insufficiently known. The calculations 

 are reduced to explicit formulae for two particular molecular 

 models : — 



(1) Elastic spheres attracting according to an inverse 

 5th power law. 



(2) Elastic spheres surrounded by a limited spherical 

 shell in which there is a constant attraction, with no forces 

 at all outside. 



* Communicated by C. G. Darwin, M.A. 

 Phil. Mag. S. 6. Vol. 43. No. 257. May 1922. 3 E 



