(Liquid + liquid) equilibrium (LLE) data for the solubility curves and tie-line compositions were examined for mixtures of {water (1) + propionic acid (2) + dimethyl succinate or dimethyl glutarate or dimethyl adipate (3)} at T = 298.15 K and atmospheric pressure, (101.3 +/- 0.7) kPa. The relative mutual solubility of the propionic acid is higher in the dibasic esters phases than in the aqueous phase. The reliability of the experimental tie-line data were confirmed by using the Othmer-Tobias correlation. The LLE data of the ternary systems were predicted by UNIFAC and modified UNIFAC methods. Distribution coefficients and separation factors were evaluated for the immiscibility region. (c) 2007 Elsevier Ltd. All rights reserved.