Abstract
Thermodynamic properties of classical polar fluids can be estimated from those of a simple fluid wherein the central pair potential has been chosen to account for pairwise orientational correlations. This mapping of polar to simple fluids has been extended to account for the quantization of rotational motion and the corresponding damping of orientational correlations. Choosing the model parameters to reflect HCl, HBr and HI we find large rotational quantum effects on the phase diagram and second virial coefficients if dispersion forces are neglected but only very minor such effects when the dominant dispersion forces are included.