The excess volume V-E, speed of sound u, and viscosity eta have been measured for the binary mixtures of dipropylene glycol monobutyl ether with butylamine, dibutylamine, and tributylamine across their entire composition ranges, at a temperature of 298.15 K and atmospheric pressure. The density values derived from the excess molar volumes were converted to molar volumes, V, which are combined with the speed of sounds to obtain estimates of the product K-S,K-m, and their excess counterparts K-S,m(E). The deviation of the speeds of sound u(D) from their ideal values u(id) in an ideal mixtures were calculated for all estimated values of mole fraction x(1). Viscosities have also been measured for mixtures of dipropylene glycol monomethyl ether and butylamine, dibutylamine, or tributylamine at the same temperature. From the experimental data, deviations in viscosity (Delta ln eta) and excess energies of activation for viscous flow (Delta G*(E)) have been derived for all systems. The Flory theory of mixtures provides a useful basis for a qualitative interpretation of the viscosity results. The theoretical values of molar isentropic compressibility of K-S,K-m and of speed of sound u have been calculated using the Prigogine-Flory-Patterson (PFP) theory with the van der Waals (vdW) potential energy model and the results have been compared with experimental values. (c) 2005 Elsevier Ltd. All rights reserved.