The Internal Pressures of Liquids 

 TABLE 4 



615 



2. The Computation of "a" from Thomas Young's Formula 



As pointed out in an earlier paper, the first method pro- 

 posed for computing the internal pressure was Young's, 

 namely : 



(12) T = rK/3 = m/V 2 3 



r being the radius of action. If r is taken at absolute zero 

 as equal to i/ /3 we have finally 



(13) 



Tv/ 3 = 



M 2 K is the factor "a" for a single molecule and v the volume 

 of a single molecule at absolute zero. In my former paper 

 D O was assumed for all except the simple gases to be v c /4, and 

 for those gases it was taken as v c /3.6. Timmermans 1 has 

 recently confirmed S. Young's finding that the rectilinear 

 diameter law gives too high values for the density at low 

 temperatures and that van der Waals is correct in taking the 

 density at absolute zero as S times the critical density, where 

 S is the critical coefficient, or RT C /V C P C , which varies with 

 different substances between 3.4 and 4. Tv 2 /3 I formerly 

 computed by Ramsay and Shields' equation assuming that it 



Timmermans: Proc. Roy. Dublin Soc., [N S] 13, 310 (1912). 



