Molar heat capacity at constant volume. Binary mixtures of 1,2-dicholroethane and 1,2-dibromoethane with cyclohexane

Abstract

The molar heat capacity at constant pressure, the velocity of sound, the thermal expansion co-efficient, and the volume change of mixing of the systems dibromoethane + cyclohexane and dichloroethane + cyclohexane has been measured over the entire concentration range. From these data, the molar heat capacity at constant volume C_v(on the saturation curve), and the isothermal and adiabatic compressibility of the two systems has been calculated. For both systems, C_v shows negative deviations from additivity. The contribution to C_v of the trans-gauche conformational equilibrium of the dihalogenethanes is estimated by means of model calculations. Earlier results on the dihalogenethane + benzene systems are also considered. The derivatives (δC_v/δT)_v and (δC_v/δV)_T are calculated for the pure liquids. A tentative estimate is made of the rotational heat capacity in the pure liquids and in mixtures.