In this paper a new method for the prediction of salt effects on VLE is proposed. The model of Pitzer(1980)is extended to the aqueous multicompo-nent electrolyte systems and mixed solvent/salt systems. After reasonable simplification

the activity coefficient expressions containing only one parameter for each binary electrolyte-solvent action are derived for the solvent and volatile solute. It is possible to predict the VLE of salt-containing systems by using these parameters which can be correlated with binary solution properties. The solvent activities of binary electrolyte solutions including 40 aqueous systems and 7 methanol solution systems are correlated to get the single-parameter of the simplified Pitzers model. Application of this model to the estimation of the vapor pressure depression in 320-403 K of LiCl

NaCl

KAc

HCl

CaCl2

MgCl2 binary aqueous solutions and LiCl

CaCl2 binary methanol solutions has shown good accuracy. The total mean of absolute deviation of 182 data points is 0.65 kPa. By the extended model and parameters correlated at 298.15K

the VLE of five different type of ternary salt-containing systems

H2O +CaCl2 +MgCl2

H2O+KCl + HCl

H2O+CaCl2 + HCl

H2O+ LiCl + CH3OH

H2O + CaCl2 + CH3OH

are predicted with the total mean of absolute deviation of 0.015 in vapor phase mole fraction

of 1 K in boiling point

of 1.92 kPa in vapor pressure.