Construction of Multicomponent Pourbaix Diagrams Using Generalized Species

A method for the construction of predominance‐zone diagrams of multicomponent and multiphase systems of chemical species in a single oxidation state, which consider the formation of mixed and polynuclear complexes (of the type ) is presented. Such diagrams may be constructed by defining generalized species, complexation coefficients (with multiplicative structure) and generalized equilibria of complexation, dismutation, polynucleation, and phase formation, with their conditional constants associated. By having these diagrams for each oxidation state of the same component, multidimensional Pourbaix diagrams are constructed. The predominance‐zone diagrams of * Eu(0), * Eu(II), and * Eu(III) in the presence of citric acid and nitrilotriacetic acid in aqueous solution, are constructed by using this approach.