Dissolution enthalpies of anhydrous sodium sulfate in water were measured up to saturation at T = (287.8, 317.5, and 352.1) K with a SETARAM C80 mixing calorimeter. Experimental isotherms, and previous ones at T = 297.6 K and T = 317.5 K (Hubert, N. et al., Thermochim. Acta 1995, 259, 41-48), all intersect around a molality of 2 mol (.) kg(-1). These five isotherms have been fitted with the electrolyte-NRTL model according to a methodology presented in this paper. This methodology uses enthalpy values along with values at T = 298.15 K from the literature and leads to the proposal of a unique set of parameters that allows a simultaneous representation of dissolution enthalpies, apparent relative molar enthalpies, and osmotic coefficients of sodium sulfate in water. Very good agreement was obtained between experimental and calculated values of dissolution enthalpies and osmotic coefficients in (water + sodium sulfate).