144 
MR. A. E. OXLEY ON THE INFLUENCE OF MOLECULAR 
In the liquid and crystalline states, providing there are no molecular complexes 
whose constitutions vary with the temperature, the diamagnetic property involves no 
temperature co-ordinate and is represented by a series of straight lines parallel to the 
temperature axis. The work of MM. Weiss and Kamerlingh Onnes has shown 
that ferro-magnetic and paramagnetic properties can be represented by a series of 
hyperbolae. In either case, I have shown that if the substance forms aggregates, or 
assumes a crystalline structure, the transition stage is represented by the equations 
X D = g . AMp (diamag.), x P = 2 (paramag.) 
which take into account the coexistence of molecular complexes of different types. 
These two expressions are generally applicable and represent the variation of 
magnetic property with temperature in terms of the two Curie laws, and the 
superposed effect of the change of molecular complexity with temperature. 
For most of the substances examined, the liquid state is more diamagnetic than the 
crystals. The cases of benzoyl chloride, phenylhydrazine and the liquid crystal 
compounds, cholesteryl chloride and para-azoxyanisol, are abnormal. Nearly all 
benzene derivatives show a change of susceptibility on crystallization, amounting to 
5 per cent, (approximate). The sign of this change is attributed to the directive 
action of the substituent. 
The experiments show that diamagnetism is not wholly an atomic property ; for 
the process of crystallization, involving simply a closer approach of the atomic spheres 
of influence, is able to modify the susceptibility. 
The existence of a gelatinous or super-cooled liquid state, possessing in all the cases 
examined a diamagnetic property equal to that of the liquid above the normal fusion 
point, corresponds to the existence of a supercooled paramagnetic state of nickel- 
steels below the critical temperature. Definite hysteresis loops with respect to 
temperature have been obtained, similar to those discovered by the late 
Prof. Hopkinson for nickel-steels. The heat of formation of the diamagnetic 
crystals corresponds to the heat evolved at the critical temperature of the nickel- 
steel. 
The constancy of the diamagnetic property when the substance supercools or passes 
into a jelly is in harmony with the constancy of the closely related phenomenon of 
the magnetic rotation of the plane of polarisation by that substance when a gelatinous 
form is assumed. The process of crystallization is accompanied by a modification of 
the susceptibility and of the magnetic rotation. 
The hypothesis of molecular distortion stated at the beginning of this communica¬ 
tion has been justified, and the interpretation of the effect of crystallization as due to 
a slight modification of the internal structure of the molecule is in agreement with 
the conceptions of chemists and crystallographers concerning the nature of crystal 
structure. 
