SOLUBILITY EQUILIBRIA - FROM CHEMICAL POTENTIOMETRY TO INDUSTRIAL APPLICATIONS

Solubility equilibria are related to thermodynamic properties in gener al and chemical potentials in particular of ionic compounds, nonelectr olytes and metals in aqueous solutions of melts. Solubility phenomena are most efficiently dealt with by the theoretical and graphical metho ds of phase theory. Master variables for the depiction of the pertinen t solid-solid or solid-liquid phase diagrams are deduced from generali zed Gibbs-Duhem equations. Solubility techniques in aqueous media cont ribute to information on thermodynamic quantities of sparingly as well as highly soluble ionic compounds, which may play a role in geochemis try and/or industry. For solving multiphase multicomponent equilibrium problems in this context the general Gibbs energy minimizing program ChemSage was used together with a new optimization routine. At the tem peratures of aqueous solutions solid-solid phase transformations and/o r recrystallizations are often much slower than equilibration between solid and Liquid phases. It is shown that thermodynamically reliable d ata from dissolution studies on metastable systems can be obtained. Fi nally the role of solubility phenomena in physical metallurgy is addre ssed. An example for the application of solubility information to an i ndustrial problem is presented.