Thermodynamic Stability of Natural Aqueous Systems

Main Focus Of The Chapter

In this chapter the thermodynamics of the precipitation-dissolution processes of the sparingly soluble salts of different nature and the arbitrary composition under the conditions of the various side reactions between the precipitated ions (solid phase) and the saturated solution components are examined. As side reactions, protonation reactions of the ligand, hydrolysis of the metal ion, formation of neutral, protonated and hydroxocomplex are considered. For this purpose, an original method of analyzing complex chemical equilibria in the presence of solid phases is used. The notion of generalized reaction equation is introduced in order to take into account all conjugated side reactions. This equation is the generalization of a set of common chemical equations, taking into account the simultaneous formation of several different chemical species. The necessity of examining a global process derives from the fact that the nature and ratio of the concentrations of the complex species resulting from the reactions depend on the ratio of the concentrations of the initial substances (metal ion and ligand), temperature and other factors (thermodynamic parameters).