Experimental Vapor Pressures and Derived Thermodynamic Properties of Aqueous Solutions of Lithium Nitrate from 423 to 623 K

Vapor pressures of six aqueous lithium nitrate solutions with molalities of (0.181, 0.526, 0.963, 1.730, 2.990, and 5.250) mol-kg^–1 have been measured in the temperature range 423.15–623.15 K with a constant-volume piezometer immersed in a precision liquid thermostat. The static method was used to measure the vapor pressure. The total uncertainty of the temperature, pressure and composition measurements were estimated to be less than 15 mK, 0.2%, and 0.014%, respectively. The vapor pressures of pure water were measured with the same apparatus and procedure to confirm the accuracy of the method used for aqueous lithium nitrate solutions. The results for pure water were compared with high-accuracy P_S–T_S data calculated from the IAPWS standard equation of state. Important thermodynamic functions (activities of water and lithium nitrate, partial molar volumes, osmotic coefficient, excess relative partial molar entropy, and relative partial molar enthalpy values of the solvent) were derived using the measured values of vapor pressure for the solution and pure water. The measured and derived thermodynamic properties for solutions were compared with data reported in the literature. The present results are consistent with most previous reported thermodynamic data for the pure water and H₂O + LiNO₃ solutions at low temperatures.