Physics. — “The quadrupole moments of the oxygen and nitrogen 
molecules”. By Prof. W. H. Krersom. (Communication N°. 6a 
from the Laboratory of Physics and Physical Chemistry of 
the Veterinary College at Utrecht). (Communicated by Prof. 
KAMERLINGH ONNES). 
(Communicated at the meeting of November 27, 1920). 
§ 1. Introduction. In Suppl. N°. 39a to the communications from 
the physical laboratory of Leiden ')it has been proved, that, as far as 
the term with the second virial coefficient, the equation of state of 
hydrogen can be accounted for in the temperature interval between 
+ 100° C. and —100° C. (according to Suppl. Nr. 39c down to 
still lower temperatures) by assuming the molecules to act on each 
other as electric quadrupoles with constant quadrupole moment’). 
Thereto the repulsions which predominate at small. distances had to 
be replaced by the forces that would act when the molecules collided 
as solid spheres of definite radius. At the same time the quadrupole 
moment of the hydrogen molecules was determined. This proved 
a configuration of the two nuclei and the two electrons constituting 
a H,-molecule to be very well possible in such a way that it has 
the demanded quadrupole moment. By these considerations it was evident 
that the molecular attractions can be explained for homopolar molecules 
too by the electric forces exerted by the nuclei and the electrons 
constituting the molecules. To show this was for the moment the 
principal purpose of those considerations. 
A comparison of the quadrupole moment demanded by the equation 
of state with that of the Bour-Drgijr model for the hydrogen molecule 
was not made because of the many difficulties that arise against 
this model, especially with respect to the magnetic properties”) Mean- 
while Burergs*) has calculated the quadrupole moment of the hydrogen 
1) These Proceedings, vol. 18, p 686. 
2) The following Communication will treat the influence on the second virial 
coefficient of the mobility of the electrons within the molecule, which finds its 
expression in the dielectric constant. 
8) Comp. Leiden Comm. N°. 39a, p. 15, note 1. At present this difficulty has 
perhaps a somewhat smaller weight than was thought then. (Added in the trans- 
lation). 
4) J. M. Bureers, Diss. Leiden 1918, p. 186. 
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