Kerr effect and dielectric polarization of solute molecules in dilute aqueous solutions

Abstract

We report the Kerr-constant increments of 25 solute molecules in water. The data are combined with density, refractive index and dielectric increments to calculate the molar Kerr constants, ∞(_mK₂), and dipole moments, µ₂, of the solute molecules in water. We use two models to calculate the internal field: Onsager's theory of a spherical cavity embedded in a continuum dielectric and a modification of that theory due to Block and Walker, who assumed a non-uniform dielectric constant near the boundary of the cavity. We compare our results for ∞(_mK₂) and µ₂ according to the two theories with their respective values derived from non-polar solvents. We find that agreement is closer when these quantities are calculated from the modified Onsager theory of Block and Walker. We discuss the significance of this result in relation to solute–water correlation effects and the non-spherical shape of these molecules.