Ultrasonic velocity and density of aqueous solutions of polypropylene glycol have been measured experimentally over the whole range of composition at temperatures T = (283. 15 to 313.15) K and atmospheric pressure. From these experimental data, the excess specific volumes, isentropic compressibility, increments of the ultrasonic velocity, and the isentropic compressibility have been determined for each composition. The results have been interpreted in light of polymer-solvent and polymer-polymer interactions. Also, the excess specific volumes, the increments of the ultrasonic velocity, and the isentropic compressibility were fitted to a variable-degree polynomial equation. (C) 2004 Elsevier Ltd. All rights reserved.