Measurements of pressure effects on excess molar enthalpies for binary mixtures of benzene and n-hexane with cyclohexane using a new calorimeter

Abstract

A new calorimeter employing a heat conduction technique has been designed for the measurement of excess molar enthalpy h E for binary mixtures under pressures up to 200 MPa. To test its performance, the heat capacity of the calorimeter containing pure water was obtained at pressures up to 100 MPa by measuring the temperature variations ΔT H while supplying heat energy W. The results adequately satisfy linear relationships between ΔT H and W at each pressure. These relationships depend clearly on the pressure changes, in a reasonable manner for a high pressure calorimeter. The excess molar enthalpies h E for (benzene+cyclohexane) and ( n-hexane+cyclohexane) were measured at 298.15 K and pressures up to the (solid+liquid) line. The results which showed large pressure effect, are consistent with those reported elsewhere from direct measurements or thermodynamic estimation using p-V m-T-x results.