CONSTITUTION AND TEMPERATURE ON MAGNETIC SUSCEPTIBILITY. 
135 
is able to modify the susceptibility appreciably. From the decrease of diamagnetism 
accompanying the crystallization of benzene derivatives, it appears that the process of 
crystallization implies the utilization of the residual forces between the molecules 
which tends to make them more normally saturated. The value of is not constant 
for the different members of the same class of compounds, and in benzene derivatives 
it is a function not only of the ring system but also of the substituent. 
Before the extent of this adjustment of the diamagnetic property—due to the 
juxtaposition of unsaturated groups—can be of value, it is necessary to examine 
different classes of compounds each containing a large number of members. 
It will have been seen that a satisfactory interpretation of the variations of the 
diamagnetic property found in this research can be given in terms of molecular theory. 
All that has been assumed concerning the structure of the molecule is that it is a 
unit which can be distorted by the near approach of other units. In order that we 
may inquire more fully into the nature of the distortion and the forces which cause it, 
we must postulate some definite structure of the molecule. We shall assume, in the 
investigation which follows (Part II.), that the molecule consists of a congeries of 
electrons ; and that the positive charges, which keep the electrons whirling in their 
orbits, are fixed in the molecule. 
For the present, looking at the problem from a purely molecular point of view, the 
hypothesis stated at the beginning concerning the molecular distortion which accom¬ 
panies crystallization, has been found justifiable, and has led to results in harmony 
with the views of chemists and crystallographers. 
Little has been said in this communication concerning the Curie law of para¬ 
magnetism, which may be written in the form 
n p . c p 
A " 
The recent work of Prof. Kamerlingh Onnes, # on the variation of paramagnetism 
at low temperatures, shows how we may interpret departures from the simple Curie 
law, x P = c/L, by a modification of the Curie constant. The above expression for 
X P shows that if the change of aggregation or the process of crystallization modifies 
the structure of the molecule, then for every type of complex p, we shall have a new 
Curie constant c p per particle of this type. In addition to this, the above expression 
provides a continuity of the magnetic property during the transition stage where 
there will be a co-existence of various types of particles. The passage from the liquid 
to the crystalline state modifies the paramagnetic as well as the diamagnetic property. 
OnnesI has shown that there is a sudden change of the value of‘x P during the 
crystallization of liquid oxygen. 
* ‘ Yersl. Kon. Ak. v, Wetensch.,’ Amsterdam, XV., p. 322, 1912. 
t ‘ Versl. Kon. Ak. v. Wetensch.,’ Amsterdam, XIV., p. 674, 1912. 
