(Liquid + liquid) equilibrium (LLE) data for (water + propionic acid + dipropyl ether) and (water + propionic acid + diisopropyl ether) were measured at T=298.2 K and atmospheric pressure. The tie-line data were correlated by means of the UNIQUAC equation, and compared with results predicted by the UNIFAC method. A comparison of the extracting capabilities of the solvents was made with respect to distribution coefficients, separation factors, and solvent free selectivity bases. (c) 2006 Elsevier Ltd. All rights reserved.