In this paper we develop the first equation of state for alcohol containing
mixtures which includes the effect of steric hindrance between the two electron
lone pair hydrogen bond acceptor sites on the alcohol's hydroxyl oxygen. The
theory is derived for multi-component mixtures within Wertheim's multi-density
statistical mechanics in a second order perturbation theory. The accuracy of
the new approach is demonstrated by application to pure methanol and ethanol
and binary ethanol / water mixtures. It is demonstrated that the new approach
gives a substantial improvement in the prediction of hydrogen bond structure of
both pure alcohol and alcohol / water mixtures as compared to standard first
order approaches