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MAJOR A. E. OXLEY ON THE INFLUENCE OF MOLECULAR 
molecule possesses no resultant magnetic moment. For example, while iron below the 
critical temperature possesses, according to Weiss, 11 magnetons to the atom, the 
molecule of ferric ^sulphate possesses 30, ferric chloride 28, sodium ferro-pyrophosphate 
26, sodium ferrous oxalate 27.* Again, nickel below the critical temperature possesses 
3 magnetons to the atom, above the critical temperature either 8 or 9 magnetons to 
the atom, while a molecide of nickel sulphate contains 16 magnetons. In general the 
number of magnetons, per molecule of a salt of a ferro-magnetic element, is large 
compared with the number of magnetons associated with an atom of the pure 
ferro-magnetic. The fact that cupric salts are paramagnetic while cuprous ones are 
diamagnetic is interesting from our point of view. Although copper is diamagnetic, 
yet a molecule of cupric sulphate contains 10 magnetons. It seems as if the large 
local atomic fields, which have been recognised in diamagnetic and ferro-magnetic 
molecules, have the power, when the molecules approach so that their fields overlap, 
to upset the equilibrium of the atoms in combination and redistribute their magnetic 
elements. This is easily possible when the great intensity of the local molecular 
field is borne in mind. In most cases a diamagnetic molecule, on account of its 
symmetry, would, under the influence of such a field, remain diamagnetic, but each 
orbit would be distorted by the field and the susceptibility of the substance would he 
slightly modified. 
(7) On some Anomalies in the Magnetic Rotation Effect. 
Diamagnetic media are in general dextro-gyric. The only exception is titanium 
chloride which is Isevo-gyric. t Paramagnetic media are sometimes dextro-gyric and 
sometimes Imvo-gyric, while the ferro-magnetic elements, iron, nickel and cobalt are 
all dextro-gyric. At present no theory seems capable of accounting for these 
anomalies and it is therefore interesting to examine to what extent the local molecular 
field may cause the effects observed. At one time it was thought that the direction 
of rotation probably depended merely on the. diamagnetic or paramagnetic property 
of the molecule, but experiment soon disproved this generalisation. Voigt | suggested 
that the production of an intense reverse field, when the external field was applied, 
would account for the effects, but no physical explanation of a possible origin for this 
intense reverse field was given. 
On the views of diamagnetic and paramagnetic polarity developed in these 
researches, the necessary fields demanded by Voigt are found in the immediate 
neighbourhood of the molecular boundary. In diamagnetic liquids the molecules have 
zero magnetic moments and their axes are distributed at random. The application of 
* ‘ Journal de Phys.,’ vol. 1, ser. v., p. 974, 1911. 
t For solutions of salts in water it should be noted that Verdet’s constant for the solute is to be 
regarded as negative if Verdet’s constant for the solvent is less than O'0130, which is the value of the 
constant for pure water at 20° C. 
I See P. Zeeman, ‘ Researches in Magneto Optics,’ p. 185. 
