ISOPIESTIC INVESTIGATION OF THE OSMOTIC AND ACTIVITY-COEFFICIENTS OF AQUEOUS MGSO4 AND THE SOLUBILITY OF MGSO4-CENTER-DOT-7H(2)O(CR) AT 298.15 K - THERMODYNAMIC PROPERTIES OF THE MGSO4+H2O SYSTEM TO 440 K

Isopiestic determinations of the osmotic coefficient of MgSO4(aq) agai nst NaCl(aq) and KCl(aq) reference standards were performed with long equilibration times ranging to 98 days. A value of the 298.15 K solubi lity of epsomite, MgSO4. 7H(2)O(cr), was also determined. The new meas urements were combined with previous thermodynamic measurements to det ermine the thermodynamic properties of the MgSO4 + H2O system from the ice-freezing line to 440 K. The thermodynamic measurements were fitte d with two different models, an ion-interaction model and a chemical-e quilibrium model. The ability of the two models to represent this syst em was examined.