Magnetic birefringence in liquids of near-isotropic molecules

Abstract

The magnetic field-induced birefringence and dichroism of several weakly birefringent liquids has been measured, both neat and in solution. Some liquids had not been measured before and others have been remeasured with a precision considerably greater than previously reported. Linear dichroism measurements yielded the expected null result for all liquids if dust had been removed. The birefringence also was found to be sensitive to the presence of dust. Care was taken to eliminate the effect of Faraday rotation on the birefringence measurements.

Field-induced molecular re-orientation and magnetic hyperpolarizability were sufficient to explain the results, except for solutions of CCl₄ and Sn(CH₃)₄, where the partial molar Cotton–Mouton constant of both components was found to be strongly composition dependent at mole fractions of CCl₄ > 0.5. An intermolecular contribution to the magnetic birefringence of CCl₄ has been proposed to explain this. It is concluded that CCl₄ should not be regarded as an inert solvent for infinite dilution studies of molecular anisotropy in weakly anisotropic solute molecules.