ABSTRACT CTS-9317812 Texas A&M Research Fdn P.I.: Philip T. Eubank New procedures are developed for use with the recent Wong-Sandler mixing rules for the prediction of mixture phase equlibria from cubic equations of state. Improvements in the apriori evaluation of both the liquid-phase parameter {SYMBOL 65 f "GreekMathSymbols"}E and the gas-phase parameter B12EOS (or K12) are made. An important new procedure is developed where the latter parameter is found from experimental measurements of the cross second virial coefficient B12Exp in the single-phase vapor mixture at low pressures. Apriori prediction of phase equlibria to high pressures and temperatures then follows when the liquid-phase parameter AE is estimated from a group-contribution method, such as UNIFAC. An order-of-magnitude analysis shows the resultant phase equlibria to be more sensitive to the gas-phase parameter B12EOS . These new procedures are most promising in the prediction (not correlation) of the phase behavior of complex systems, such as CO2/H2O/oil in petroleum reservoirs undergoing CO2 and/or steam flooding.