Vapor-liquid equilibrium (VLE) at 101.3 kPa has been determined for diisopropyl ether + ethanol + 2,2,4-trimethylpentane ternary system, as well as for diisopropyl ether + ethanol and diisopropyl ether + 2,2,4-trimethylpentane (isooctane) binary systems. A minimum boiling azeotrope was found in the diisopropyl ether + ethanol system, while no azeotrope was observed in the diisopropyl ether + 2,2,4-trimethylpentane system or in the ternary system. Calculations of nonideality of the vapor-phase were made with Soave-Redlich-Kwong equation of state. The thermodynamic consistency of the binary VLE data was examined by both the direct test of Van Ness and the method of Kojima et al. The VLE data of the ternary system passed the thermodynamic consistency test of the McDermott-Ellis method as modified by Wisniak and Tamir. The activity coefficients of the binary mixtures were satisfactorily correlated as a function of mole fraction with the Wilson, NRTL, and UNIQUAC models. The models with their best-fitted binary parameters were used to predict the phase equilibrium behavior of the ternary system. (c) 2006 Elsevier B.V. All rights reserved.