124 



(f/- = 46°) corresponds (o (lie smallest distance between the centres 



o 



of two neighbouring molecules. Formula (1) gives for this 2,4 A. 



The further examination of the blackening in the diffiaction image 

 of the liquids thus gives a direct method of research for the way 

 in which the molecules are distributed in the liquid as to their 

 mutual distances. Some conclusions may be drawn then also on the 

 field of force of the molecules. 



The fact, tliat in water a relatively great number of pairs of 

 molecules occurs with a distance smaller than the normal one will 

 be related with the peculiarities in the thei modynamic properties 

 by which water is regarded as an associating substance. However, 

 we do not find an extraoi'dinarily great number of double or multiple 

 molecules which should have been formed by juxtaposition of sim|)le 

 molecules so as to ly as close as possible to each other. 



§ 7. O.vygen and argon. By analogous considerations as in § 6 

 we |)robably must ascribe the second weak ring for oxygen and 

 argon to pairs of molecules which touch each other '). 



According to (Ij this would give for the distance of the centres 



o o 



for oxygen 2.4 A, for argon 2.3 A. 



Because of the last remark of ^ 5 these values might however 

 still undergo a small variation. 



Comparing these results with those obtained for water we find : 

 firstly, that in oxygen and argon there is a considerably smaller 

 nuiïjber of pairs of molecules with a distance below the normal one, 

 secondly that for oxygen and argon in the greater part of these 

 molecule-pairs the molecules are Ij'ing together as close as possible. 



We might ascribe this different behaviour to a difference in the 

 fields of force: the water should have then a more intense field, 

 which extends over a greater distance, while oxygen and argon 

 should have a field of force which makes itself niore felt in the 

 immediate neighbourhood of the molecule. In this way the dipolar 

 character of the water molecule becomes manifest on one hand, the 

 quadrupolai' (resp. [lerhaps octopolar) character of the oxygen and 

 the argon molecule (atom) on the other hand. 



1) See also p. 122 note 1. 



