Kerr effect in water + dioxan solutions

Abstract

The Kerr constants, densities and refractive indices of the water + dioxan mixture over the whole composition range are reported. The molar Kerr constant of H₂O extrapolated to infinite dilution in dioxan is found to be ∞(_mK₂)= 2.3 × 10^–27 C² m⁵ J^–2. The components of the polarizability tensor of H₂O are calculated by two approaches, using light scattering data and a bond additivity method. Both give the same result within experimental error: α_xx= 1.69 ± 0.04, α_yy= 1.9 ± 0.2, α_zz= 1.3 ± 0.2 (in units 10^–40 C² m² J^–1), where x is the dipolar axis and z is normal to the molecular plane. The Kerr effect over the whole composition range is interpreted according to a theory of Hasted, proposed for the dielectric polarization of organic + aqueous mixtures. We find that the structure of water increases on addition of dioxan up to x_D= 0.2, x_D being the mole fraction of dioxan, and then decrease, in apparent contradiction to the results from dielectric polarization which indicate a monotonic decrease in the structure of the water + dioxan mixture.