Internal Pressure of a Liquid to its Dielectric Capacity. 1 1 1 



" specific susceptibility," which is in turn the susceptibility 

 k divided by the density of the substance. I have carried 

 out the recalculation of jjl for a number o£ substances from 



the data given by Pascal. If the expression it — — j is near 



the truth, one may expect that for substances the molecular 

 volumes of which are not very different, a large value for it 

 should accompany a small value for /j,, and vice versa. The 

 following table contains the values of //, and it (the latter 

 being the minimal values already obtained). 



Substance. 



Molecular volume 

 atO° C. 



ft. 



ir (atmospheres 

 per cm. 2 ). 





1096 c.c. 

 1032 

 99-29 

 104-8 

 100-5 

 108'7 



9,89224 

 0-9,90124 

 0-9,91240 

 0-9,91852 

 09,92842 

 0-9,93628 



1512 





1429 





1393 





1144 



Ethyl ether 



Methyl propionate ... 



653 



688 



The substances are arranged in order of ascending values 

 of fju. It is evident that the smaller the value for fju the 

 laro-er the value for 7r, a result which is in agreement with 

 theory and is the complementary relation to that of Obach 

 and Walden. (The last two substances mentioned stand 

 indeed in inverted order, but the value of tt is practically 

 the same for both, and slight experimental error would have 

 large influence upon their relative positions.) 



It will be observed at the same time that //, for these (and 

 other) substances is very nearly unity, so much so that as 



far as numerical values for — 2 go, the expression is identical 



with that of van der Waals, and since van der Waals' ' : a ,s 

 is generally considered to vary with T and V, one may 

 anticipate a similar result in the above expression also. 

 Hence, although the foregoing considerations point to the 

 existence of electromagnetic attraction between molecules, 

 attraction of this nature does not completely account for the 



phenomenon of cohesion, and in addition to the term 



which appears as a correction term in an equation of state 

 of the van der Waals* type, another term or terms require to 

 be introduced as well — if we are to retain this type of 

 equation at all. To proceed in this direction it is necessary 

 to consider the magnetic properties of liquids from the 

 electron standpoint. 



fir 



