In this study, binary and ternary VLE data have been determined at 5, 7.5, and 10 kPa for the system monochloracetic acid (MCA) + dichloroacetic acid (DCA) + diethylene glycol dipentyl ether (DGDP). The extractant DGDP enhances the relative volatility of the MCA/DCA system from 1.2 without extractant up to 4. The non-ideal behavior in the liquid and vapor phase was reasonably well correlated with the NRTL and Hayden-O'Connell (HOC) model, respectively. The binary and ternary VLE data were correlated separately to obtain a better description of both datasets. (c) 2012 Elsevier B.V. All rights reserved.