Thermodynamics of Multicomponent Electrolyte Solutions: Aqueous Mixtures of Two Salts from Among NaCl, KCl, NaH(2)PO(4), and KH(2)PO(4) at 25 degrees C

Five of the six possible aqueous two-salt mixtures from among NaCl KCl, NaH(2)PO(4), and KH(2)PO(4) have been studied by the isopiestic method at 25 degrees C. The sixth mixture, NaCl-KCl, has been studied previously. The deviations from ideal mixing behavior are described by a series of coefficients which were found by regression analysis. The eoefficients were used to calculate the excess Gibbs energies of mixing for equal ionic strength fractions of each salt and the trace activity coefficient of each salt at an ionic strength of 2 mole-kg(-1). The cross-square mixing rule is obeyed within experimental uncertainty for the excess Gibbs energies of mixing.