Isothermal vapour-liquid equilibria for the four binary mixtures formed by an isomer of chlorobutane (1-chlorobutane, 2-chlorobutane. 2-methyl-1-chloropropane, or 2-methyl-2-chloropropane) and diisopropyl ether has been studied at T=288.15 K, 298.15 K. and 308.15 K. The experimental data have been satisfactorily checked for thermodynamic consistency using the method of van Ness. The isothermal vapour-liquid equilibrium data have been correlated using the Wilson equation and excess Gibbs energies have been calculated. Moreover, we have measured excess enthalpies at T=298.15 K using an isothermal Row calorimeter; combining these excess enthalpies with excess Gibbs energies the corresponding entropic contributions to excess Gibbs energy have been obtained. The group contribution method UNIFAC has been used to predict the phase equilibrium behaviour of the mixtures at isothermal conditions. (C) 2011 Elsevier B.V. All rights reserved.