The dissolution enthalpy of sodium chloride in water was measured until saturation at 24.4 degrees C, 44.3 degrees C and 59.2 degrees C using a C80D differential calorimeter (SETARAM). The experimental data were fitted using Fitter’s ion interaction model and the value of the dissolution enthalpy per mole of salt at infinite dilution was found at each temperature by treating <(Delta(sol)H(infinity))over bar> as adjustable parameter. Using these calorimetric measurements, the analytical expression of the variation of Fitter’s parameters were established with respect to temperature. The validation of this expression is made by the measurement of vapour equilibrium of binary solution {H2O-NaCl} closed to saturation. Excellent agreement between experimental and calculated values of water activity has been found using our Pitzer’s model parameters.