Low-frequency dielectric dispersion and electric conductivity near the consolute point in some binary liquid mixtures

We report on detailed results for the dielectric constant ϵ and the electric conductivity σ near the consolute point in the binary liquid mixtures benzonitrile-isooctane, nitroethane-cyclohexane and nitrobenzene-isooctane. The temperature dependence of the amplitude of the observed low-frequency Maxwell-Wagner critical dispersion can be understood on the basis of a droplet model for the critical fluctuations. A novel type of critical anomaly was observed for the conductivity σ in the homogeneous phase for some of the samples with sufficiently low ionic impurity conduction. Its temperature dependence can be explained qualitatively by invoking also the droplet picture for the critical fluctuations.