(Liquid + liquid) equilibrium (LLE) data of the solubility (binodal) curves and tie-line end compositions were examined for mixtures of {water (1)+butyric acid (2) + ethyl propionate or dimethyl phthalate or dibutyl plithalate (3)} at T=298.15K and (101.3 +/- 0.7) kPa. The relative mutual solubility of the butyric acid is higher in the layers of esters than in the aqueous layer. The reliability of the experimental tie-line data was confirmed by using the Othmer-Tobias correlation. The LLE data of the ternary systems were predicted by UNIFAC method. Distribution coefficients and separation factors were evaluated for the immiscibility region. (c) 2007 Elsevier Ltd. All rights reserved.