Liquid-liquid equilibrium (LLE) data for the quaternary systems of [water + acetic acid + mixed solvent (dipropyl ether + disopropyl ether)] were measured at 298.2 K and atmospheric pressure, using various compositions of mixed solvent. Binodal curves and tie-lines for the quaternary systems have been determined in order to investigate the effect of solvent mixture, dipropyl ether (DPE) and diisopropyl ether (IPE), on extracting acetic acid from aqueous solution. A comparison of the extracting capabilities of the mixed solvents was made with respect to distribution coefficients, separation factors, and solvent free selectivity bases. Reliability of the data was confirmed by using the Othmer-Tobias and Hand plots. The tie-lines were also correlated using the UNIFAC model. The average root-mean-square deviations between the observed and calculated mass fractions for the studied systems were in the range of 10-14%. (C) 2010 Elsevier BM. All rights reserved.