Abstract: The isobaric vapor-liquid equilibrium data at 760mm Hg of two ternary systems, ethyl acetate-benzene-toluene and carbon tetrachloride-ethyl acetate-benzene, are determined by a modified Colburn equilibrium still. The composition of ethyl acetate-benzene-toluene ternary system is determined from two properties, refractive index (nD20) and normal boiling point, while the composition of carbon tetrachloride-ethyl acetate-benzene ternary system is determined from refractive index (nD20) and density (d425). The experimental equilibrium data of two ternary systems are correlated by the equation obtained from copolymerization in the field of polymer chemistry with characteristic constants merely related with the corresponding pure components. The results of both two ternary systems are fairly satisfactory.