On the use of semiempirical electrolyte theories for the modeling of solution chemical data

Abstract

In order to compare thermodynamic data on complex formation reactions, protolytic, redox and solubility equilibria determined in ionic media of various types, it is necessery to refer them to a common standard state, usually with pure water as the solvent. This requires estimates of the activivity coefficients of reactants and products. We have compared the Brønsted-Guggenheim-Scatchard specific ion interaction (SIT) model and the Pitzer models and shown that they for all practical purposes are equivalent, for the description of the ionic medium/ionic strength dependence of concentration equilibrium constants for ionic strengths up to 3 to 4 m. Equations relating the SIT specific ion interaction coefficients ε(i,j) and the Pitzer parameters β(o) and β(1) for ionic components, and Δβ(o)(0) and Δβ(1), for reactions are presented.