Modelling of multicomponent salt systems : Application to sea water and brines I. Derivation of the model

The solubility of a salt in saturated solution is described in terms of heterogeneous reaction between solid and liquid and an equation of the solubility field is established for each solid phase (limiting or intermediate phase) of a multicomponent aqueous salt system. The model supposes that solid phases are stoichiometric and that the solution is a strong electrolyte. It includes all sub-systems and the procedure used for the calculation of coefficients is described. The equations allow the critical evaluation of solubility data, the calculation of phase diagrams and the determination of equilibrium (proportion and nature of phases) under any conditions of temperature and composition. The application to the sub-systems involved in sea water and natural brines will be developed in forthcoming publications.