Perturbation theory of dipolar hard spheres: The vapour—liquid equilibrium of strongly polar substances

Abstract

Thermodynamic perturbation theory is applied to a fluid of polarizable dipolar hard spheres. Calculations of vapour—liquid equilibrium (VLE) are carried out and the vapour pressure, heat of vaporization and the densities of both coexisting phases are obtained. The inverse procedure allows the determination of effective potential parameters by fitting some experimental vapour pressure data. Using these parameters the thermodynamic properties of the VLE can be extrapolated to temperatures close to the critical point. For some strongly polar substances an excellent agreement between the predicted vapour pressure and the experimental results was found. Thus the perturbation theory provides a very successful procedure for predicting vapour pressures over a wide range of temperature.