Thermodynamics of electrolytes in aqueous systems containing both ionic and nonionic solutes. Application of the Pitzer-Simonson-Clegg equations to activity coefficients and solubilities of 1 : 1 electrolytes in four electrolyte-non-electrolyte-H2O ternary systems at 298.15 K

The Pitzer-Simonson-Clegg equation is applied to the salt activity coeffici ents and solubilities in ternary systems NaCl-sucrose-H2O, NaCl-urea-H2O, N aCl-mannitol-H2O, and KCl-glycine-H2O at 298.15 K. The results are compared with the isopiestic, emf, and solubility measurements. The model with a ze ro parameter (Y-l,Y-n,Y-MX) relating interactions between two neutral speci es and two ions is valid at high electrolyte:non-electrolyte ratios. The in troduction of the macroscopic relative permittivity, the mean molar mass, a nd the density of non-electrolyte-H2O mixture in the Debye-Huckel constant and the "closest approach'' parameter significantly worsens the model calcu lations. The model predictions are also slightly worsened if a constant non zero Y-l,Y-n,Y-MX is added. The accuracy of the model at lower salt proport ions can be considerably improved by making the parameter Y-l,Y-n,Y-MX depe ndent either on ionic strength or on ionic strength and mole fraction of no nionic solute. Under these conditions, the model can provide good descripti on of salt activity coefficients and solubilities over entire experimental composition ranges. These results suggest that a composition dependent para meter Y-l,Y-n,Y-MX is needed for the present four systems.