Predictions of Activity Coefficients of Nearly Athermal Binary Mixtures Using Cubic Equations of State

It is shown that cubic equations of state of the van der Waals family predict the ideal behavior of athermal solutions at infinite pressure. An expression for the infinite-dilution activity coefficient in binary mixtures is derived from the Soave−Redlich−Kwong (SRK) equation of state. The nonresidual contribution of this expression is used to predict the activity coefficients of athermal mixtures. In this work, we compare experimental infinite-dilution activity coefficients with predictions from different models. The comparison shows better agreement of the present model for light linear and branched alkanes diluted in normal alkanes of 20−36 carbon atoms.