Proper lies of a Molecule in a Substance. 107 



given by 3—^. The data were obtained from Landolt and 

 te J m a d 



Bornstein's tables. It will be seen that the values of n in the 



former case are much larger than in the latter. 



Table I. 



Ether, C 4 H 10 O. 



Ethyl Chloride, C 2 H fi Cl. 



i 



t 



13/5 



78-5 



T- 



wlO- 26 . 



» io- 25 



(as perf. gas). 



t. 



4 



wlO" 26 . 



rclO- 25 

 (as perf. gas). 



2669 



1812 



7-1 

 44 



6-24 

 6 16 



ii 



99 



3383 

 2042 



9-9 

 6-1 





Pentane, C.H 12 . 



Chloroform, CHC1 3 . 







60 

 1 



1747 

 1260 



49 

 3-2 



5-23 



5-68 



1 



2991 



60 j 2726 



i 



6-5 

 54 



6-30 



6-50 



This result is due to two causes. One of them is that the 

 actual volume occupied by the molecules is comparable with 

 that occupied by the matter as a whole. Consequently the 

 molecules have not so much room for motion as if they 

 consisted of points, which increases their frequency of col- 

 lisions and change of direction of motion, and thus increases 

 the value of n. The other cause is the attraction that exists 

 between the molecules. It has the effect of making two 

 molecules about to collide to pass over their distance of 

 separation more quickly than if they exerted no attraction 

 upon one another. The attraction thus has the effect of 

 increasing the average velocity of each molecule and con- 

 sequently the value of n. 



The quantity n can be expressed in terms of more funda- 

 mental quantities than those contained in equation (1). In 

 previous papers * I have shown that 



p=w(ff\z^y 



and 



K. 



($"<*'«# 



where M 2 and K 2 are quantities which have the same value 



* Phil. Mag. Dec. 1909, p. 903 ; and May 1910, p. 788, and Oct. 1910. 

 p. 668. 



