CRITICAL-EVALUATION OF THERMODYNAMICS OF COMPLEX-FORMATION OF METAL-IONS IN AQUEOUS-SOLUTIONS .1. A DESCRIPTION OF EVALUATION METHODS

An important step for the reliable evaluation of the thermodynamics of aqueous complex species is the appropriate choice of a model for inte rpolation and extrapolation of experimental values of log K and Delta( r)H of complex formation reactions in different ionic media. Several m odels proposed for the representation of activity coefficients in aque ous solutions are briefly discussed. It has been shown that, at the pr esent state of the art, with a small number of experimental determinat ions of limited accuracy, the Bronsted-Guggenheim-Scatchard specific i nteraction (SIT) model is the most suitable method for evaluating the values of log K degrees and Delta(r)H degrees at infinite dilution and for reproducing the dependence of log K and Delta(r)H on the ionic me dium and concentration. The analytical expressions needed to represent the dependencies of log K and Delta(r)H of complex formation reaction s have been derived on the basis of the SIT model. As an example of us ing the SIT model, the experimental data of water dissociation in diff erent ionic media and concentrations have been critically treated to e valuate the values of log K degrees and Delta(r)H degrees, as well as the respective values of Delta epsilon for different ionic media. The application of the SIT model has also been demonstrated for the repres entation of CuO(cr) solubility and Cu2+ hydrolysis in various ionic me dia.