1131 
cules due to the quadrupolar forces is then, according to the above 
mentioned communication, *): 
lg =v, —- ¥ > oS AV Meets) 
r 
in which 
Pe AB cos P AG cos apel ee ER 
and 
A = 2 (13 cos* 0) (1-3 cos? 0) 
B= 16 sin 9, cos G, sin 4, cos O, Ee a vee 
C= sn Dan 0. | 
Here 
3,” 
Me Fe. Mentha. guy dese (7) 
(u, = quadrupolar moment) is the potential energy due to the qua- 
drupolar forces, when the molecules are in contact while the two 
quadrupolar axes are perpendicular to each other and to the line 
connecting the centres ’). 
The potential energy of the pair of molecules ane to the magnetic 
dipoles is given by °*) 
o? 
i ae aed RE ih meres iy sO) 
in which 
ee 
Un or . . . . . . . . . . (9) 
(u, = magnetic dipolar moment), and 
B= 2 cos 6, cos 0, + sinO, snO,cosp . . . . (10) 
For the potential energy of the magnetic dipoles in the magnetic 
field we find 
Wy = RA eg dee. at =). on CLE) 
in which 
$2 = cos x (cos 0, — cos 6,) — sin x {sin O, cos Wp + sin O, cos (W + p)}. (12) 
1) Comp. also these Communications No. 6b § 3, These Proceedings 23, 
p. 943, 1920. As, in this paper, we have only to do with pairs of molecules 
and not with groups of three and more, we shall simplify the notations for 
the energy by writing for example for the potential energy of a definite pair 
of molecules uw, while until now we have written zp). 
3) In this paper we shall neglect the action of induction between the 
molecules. In Comm. No. 66 it has been proved that this action is of no 
importance compared with that of the quadrupoles. 
5) Leiden Comm. Suppl. No. 246 § 6. These Proceedings June 1912, p. 256. 
73* 
