Determination of stability constants of complexes of MiKjHkL type in concentrated solutions of mixed salts

This paper suggests a non-conventional approach towards the correct determination of stability constants K-ijk of mixed complexes from the results of potentiometric titrations. The method is based on inaccurate (in principle) results of titrations made in isomolar titrand-titrant systems. The data thus obtained are validated on the basis of relationships between log K-ijk and relative error (%e) of the determination of an analyte concentration. Accurate values for K-ijk are calculated for the set (ijk) of possible complexes. The accuracy depends on the degree of linearity between the variables considered. The model obtained was thoroughly tested on the system containing malonic acid together with sodium and potassium nitrates. (C) 1999 Elsevier Science B.V. All rights reserved.