Solid‐solute phase equilibria in aqueous solution. IV. Calculation of Phase Diagrams

Abstract

Abstract The thermodynamic principles of conventional (T‐ x , P‐T) phase diagrams and solubility (log ΣK‐ x ) diagrams depicting solid‐solute phase equilibria in aqueous solution are derived from a unifying point of view. It is shown that thermodynamic quantities necessary for the construction of conventional phase diagrams can be obtained from solubility measurements. The unary system calcite‐aragonite and the binary system aragonite‐strontianite, where solubility data are available over the whole compositional range, have been selected as examples. In the latter case, the constraint of constant composition of the solid phase leading to a metastable equilibrium with the respective solute species is an essential point in the thermodynamic derivation and was observed experimentally as well.