High frequency dielectric behaviour of critical binary solutions of benzonitrile-isooctane

Abstract

The high frequency dielectric behaviour of critical binary mixtures of benzonitrile-isooctane is described, as a function of temperature, for two concentrations and for a frequency coverage comprising several discrete values between 3 and 112 GHz and a continuous range between 600 and 3600 GHz. For the first time, the precritical region is explored using far infrared spectroscopy and the temperature dependence of the refractive index and the absorption is reported. As the temperature approaches the critical value, the Cole-Davidson diagrams are found to show a progressive flattening, which can be characterised by a decrease in β, the Cole-Davidson coefficient. Both the microwave and the far-infrared properties are strongly anomalous near the consolute temperature and this could be consistent with the assumption of growing microscopic regions within the liquid, near this temperature.