Molar heat capacity of binary liquid mixtures: 1,2-dichloroethane + cyclohexane and 1,2-dichloroethane + methylcyclohexane

Abstract

The molar heat capacity at constant pressure, C P, of the two binary liquid mixtures 1,2-dichloroethane + cyclohexane and 1,2-dichloroethane + methylcyclohexane were determined at 298.15 K from measurements of the volumetric heat capacity, C P/ V, in a Picker flow microcalorimeter ( V is the molar volume). For the molar excess heat capacity, C P E, the imprecision of the adopted stepwise procedure is characterized by a standard deviation of about ± 0.05 J K −1 mole −1, which amounts to ca. 3% of C P E. Literature data on ultrasonic velocities, on molar volumes, and on coefficients of thermal expansion were used to calculate the molar heat capacity at constant volume, C v, and the isothermal compressibility, β T, of the pure substances, as well as the corresponding excess quantities C V E and ( Vβ T) E of the binary mixture 1,2-dichloroethane + cyclohexane. A preliminary discussion of our results in terms of external and internal rotational behavior ( trans-gauche equilibrium of 1,2-dichloroethane) is presented.