Density, sound velocity and electrical conductivity of solutions of tri-sodium phosphate (Na3PO4) in 1-propanol + water mixed-solvent media with alcohol mass fractions of 0.00, 0.05, 0.10, and 0.15 are reported in the 283.15-303.15 K temperature range at 5 K intervals. From the experimental density and sound velocity data, the apparent molar volume and isentropic compressibility values of tri-sodium phosphate are evaluated and fitted to a Redlich + Meyer type equation from which the apparent molar volume and apparent molar isentropic compressibility of the solutions at the infinite dilution are calculated at working temperature. The results show a positive transfer volume of Na3PO4 from an aqueous solution to an aqueous 1-propanol solution. The apparent molar isentropic compressibility of Na3PO4 in aqueous 1-propanol solutions is negative and it increases with increasing concentration of Na3PO4, 1-propanol and temperature. The effects of the electrolyte concentration, temperature and relative permittivity of the medium on the molar conductivity are also investigated. Comparisons between the results obtained in this work are made with those for Na2HPO4 and NaH2PO4 obtained in our previous works. (c) 2008 Elsevier B.V. All rights reserved.