DISSOLUTION ENTHALPY OF NACL IN WATER AT 25-DEGREES-C, 45-DEGREES-C AND 60-DEGREES-C - DETERMINATION OF THE PITZER-PARAMETERS OF THE (H2O-NACL) SYSTEM AND THE MOLAR DISSOLUTION ENTHALPY AT INFINITE DILUTION OFNACL IN WATER BETWEEN 25-DEGREES-C AND 100-DEGREES-C

The dissolution enthalpy of sodium chloride in water was measured unti l saturation at 24.4 degrees C, 44.3 degrees C and 59.2 degrees C usin g a C80D differential calorimeter (SETARAM). The experimental data wer e fitted using Fitter's ion interaction model and the value of the dis solution enthalpy per mole of salt at infinite dilution was found at e ach temperature by treating <(Delta(sol)H(infinity))over bar> as adjus table parameter. Using these calorimetric measurements, the analytical expression of the variation of Fitter's parameters were established w ith 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 ca lculated values of water activity has been found using our Pitzer's mo del parameters. (C) 1997 Elsevier Science B.V.