Densities and speeds of sound at atmospheric pressure and temperatures of (283.15, 298.15, and 313.15) K for the binary mixtures formed by n-hexane or n-heptane with isomeric chlorobutanes were determined. Afterwards excess volumes, excess isentropic compressibilities and excess speeds of sound were calculated using the experimental data and correlated using a Redlich-Kister type equation. Finally, the results were studied using the Prigogine-Flory-Patterson theory showing excellent predictions for speed of sound and isentropic compressibility values of mixtures as well as a strong influence of the interactional contribution term for excess volume values. (C) 2010 Elsevier Ltd. All rights reserved.