Lagrange interpolation method for the calculation of stability constants of complex equilibria in solution phase

Abstract

A numerical (Lagrange) interpolation procedure has been used for calculating the stepwise formation constants of overlapping and non-overlapping equilibria in aqueous and aquo-organic mixtures. In order to test the validity of the procedure-for chemical equilibria, proton-ligand complexes of various complexities have been simulated using a computer program (subroutine BARN). Error-free stability constants are obtained with the interpolation procedure for non-overlapping equilibria. The apparent deviations observed in the case of overlapping equilibria have been rationalized on the basis of a new additivity model for correction terms. A third order polynomial is found to be sufficient for proton-ligand equilibria of chemical interest. The procedure is carried out using a computer program (Fortran 77 subroutine LANIN).