REFORMULATION OF WONG-SANDLER MIXING RULE FOR CUBIC EQUATIONS OF STATE

The cubic equation of state mixing rule of Wong and Sandler is reformu lated in a way that eliminates one of its parameters and so that it ca n go smoothly from activity coefficient-like behavior to the classical van der Waals one-fluid mixing rule merely by variation of its parame ters. The parameters in the reformulated mixing rule can be obtained f rom correlation of vapor-liquid equilibrium data or from the two infin ite dilution activity coefficients for each binary pair in the mixture . When these activity coefficients are estimated from the UNIFAC group contribution model the mixing rule becomes completely predictive. The correlative and completely predictive forms of this mixing rule are t ested here and shown to be accurate for five difficult binary systems and one ternary mixture over large ranges of temperature and pressure.