Excess molar enthalpies of nitrous oxide–toluene in the liquid and supercritical regions

Abstract

The excess molar enthalpies H^E of [x N₂O +(1 –x)C₆H₅CH₃] have been measured in the liquid and supercritical regions over the whole concentration range. Mixtures at a temperature of 308.15 K and pressures of 12.27 and 15.00 MPa show moderate endothermic and exothermic mixing in the toluene-rich region and nitrous oxide-rich region, respectively. Mixtures at 308.15 K and 9.49 MPa and at 323.15 K and 12.27 and 15.00 MPa show moderate exothermic mixing. Mixtures at 323.15 K and 7.64 and 9.49 MPa show significant exothermic mixing. The changes observed in the excess enthalpy with temperature and pressure have been discussed in terms of liquid–vapour equilibrium and critical constants for nitrous oxide–toluene. The experimental values of H^E at 308.15 and 323.15 K and those previously reported at 313.15 K have been analysed using the Peng–Robinson equation of state.