EXCESS MOLAR ENTHALPIES OF NITROUS-OXIDE TOLUENE IN THE LIQUID AND SUPERCRITICAL REGIONS

The excess molar enthalpies H-E of [XN(2)O + (1 - X)C6H5CH3] have been measured in the liquid and supercritical regions over the whole conce ntration range. Mixtures at a temperature of 308.15 K and pressures of 12.27 and 15.00 MPa show moderate endothermic and exothermic mixing i n 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 an d 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 nitr ous 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.