Vapor pressures of four aqueous lithium sulfate solutions (0.279, 0.886, 1.322, and 1.600 mol kg(-1)) have been measured in the temperature range from 423.15 to 573.15 K with a constant-volume piezometer immersed in a precision liquid thermostat. The static method was used to measure of vapor pressure. The total uncertainty of temperature, pressure, and composition measurements were estimated to be less than 10 mK, 0.2, and 0.014%, respectively. The vapor pressures of pure water were measure to confirm the accuracy of the method for aqueous lithium sulfate solutions taken from the apparatus and procedure of measurements. The results for pure water were compared with high-accuracy P-S-T-S measurements by other authors and with values calculated from IAPWS formulation. Useful thermodynamic functions (water activities, excess relative partial molar entropy, and relative partial molar enthalpy values of solvent) were derived using measured values of vapor pressure for the solution and pure water. The measured and derived thermodynamic properties for solution were compared with data reported in the literature. Present results are consistent with most of the previous thermodynamic data for the pure water and H2O + Li2SO4 solutions. (C) 2003 Elsevier B.V. All rights reserved.