Pure and Applied Chemistry

Abstract: In this paper the application of Pitzer's equations for modeling of solubility equilibria in the hexary oceanic salt system Na⁺, K⁺, Mg²⁺, Ca²⁺ // Cl­, SO₄²­­H₂ O and its subsystems over large temperature intervals is discussed. Lack of ternary solution data considerably restricts the use of the equations as an evaluation tool for the quality of solubility data. Models optimized for the available data in two temperature intervals have been derived. Since Pitzer's model gives no guidance for temperature dependence, the number of parameters is dominated by temperature coefficients. Thus, for extended temperature intervals other approaches like the Cohen-Adad formalism can be advantageous in solubility data evaluation.