All mixing coefficients and consistency test calculations for binary mixed electrolytes

Two new methods are reported from which the mixing activity coefficients of both electrolytes in a binary mixture can be computed simultaneously from fitting the activity coefficients of one of the electrolytes only and without using the derivatives of the parameters. Furthermore, variations caused by changing the fractional ionic strengths at fixed total ionic strength entails no assumptions about the ionic strength dependence of the mixing coefficients. The methods are shown to be superior to other methods. The results for the system HCl+KCl at 25°C are discussed.