132 
ME. A. E. OXLEY OX THE INFLUENCE OF MOLECULAR 
the substance assumes a gelatinous or liquid form is in accordance with the constancy 
of the magnetic property which is observed when the substance super-cools or passes 
into a jelly. Until we postulate some definite internal structure of the atom or 
molecule, it is impossible to say what the precise effect of the adjustment, from the 
symmetrical shape of the molecule of the gelatinous state to the non-symmetrical shape 
of the crystalline state, will be, either as regards magnitude or sign. 
Providing the molecular complexity does not change, the diamagnetic property does 
not depend upon the temperature, and it can therefore be represented by a series of 
straight lines parallel to the temperature axis. Continuity between these straight 
lines is represented by the equation 
X D =| 2w r AM ?.( x ) 
During the transition from one state to another, different types of particles co-exist, 
n p characterizing the growth of the number of particles of type p. AM ? , the* 
diamagnetic moment produced by the applied field H, in a complex of type p, is 
dependent upon the molecular distortion of the complex. 
In the crystalline and liquid states, 
X Dc = g • X Di = g • 
where AM C and AMj are the diamagnetic moments produced in a distorted molecule of 
the crystalline and liquid states respectively, and N is the number of molecules per 
gramme of the substance. The magnitude and sign of the change of susceptibility will 
be determined by the nature of the crystalline structure, while the shape of the curve of 
transition* depends on the variation of n p with temperature. 
Below the melting points of benzaldehyde, benzophenone, and phenylhydrazine, two 
distinct x — ^ curves have been obtained. In each case the velocity of crystallization 
of the super-cooled liquid was small, for observations showed that, several hours after 
cooling, the susceptibility of the gelatinous state was indistinguishable from that of 
the true liquid. 
For benzene derivatives, the diamagnetic property of the crystalline state is in 
general less than that of the liquid state; but in addition to those compounds which 
show a liquid crystal state, there are two important exceptions, viz., benzoyl chloride 
and phenylhydrazine, in which the crystals are more diamagnetic than the liquid. 
It is interesting to notice that there exists for benzene and its derivatives an 
alternative kind of packing which is found in the crystalline structure of some of the 
halogen derivatives. This alternative or cubic system is highly symmetrical for 
* In the experiments which have been described the shape of this curve is masked by the effect of low 
thermal conductivity of the substance. 
