Protolytic and coordination equilibria in aqueous solutions of nickel(II) complexonates

Abstract

Protolytic and coordination equilibria in ternary systems containing a nickel(II) salt, ethylenediaminetetraacetic acid, and monoamine complexones, such as iminodiacetic, hydroxyethyliminodiacetic, and nitrilotriacetic acids, were studied by absorption spectroscopy against the background of NaClO4 at I = 0.1 and T = (20 ± 2)°C. Experimental data were processed by mathematical models that were able of evaluating the possibility of existence of a wide spectrum of species in solution and to select the species sufficient for the experimental data to be reproduced from them. The compositions of polynuclear heteroligand complexonates were determined, the pH regions of their existence were established, and the equilibrium constants of reactions and the stability constants of the complexes were calculated.