Invariant Equilibria in Multicomponent Systems

The translation method for predicting and constructing equilibrium phase diagrams of multicomponent systems is developed based on the compatibility of structural elements of partial constituent ( n- component) systems and the general ( n + 1)-component system with account for the requirements of the Gibbs phase rule. The invariant equilibrium states in the five-component system NaCl – KCl – MgCl 2 – CaCl 2 – H 2 O at 25°C are studied. This multicomponent system features the options of invariant equilibria where one and the same composition of equilibrium solid phases can be in equilibrium with saturated solutions of differing concentrations. Therefore, this invariant equilibrium is to be reflected in the diagram as a geometric (invariant) image that has a dimension (it may be conventionally referred to as a quasi-point) and not by a point. The dimension of this image is determined by the concentration bounds of components in the equilibrium saturated solution.