Nickel(II) complexes with 2-hydroxyethyliminodioacetic acid in aqueous solutions of dicarboxylic acids

The equilibria in binary and ternary systems containing a nickel(II) salt, 2-hydroxyethyliminodiacetic acid, and dicarboxylates were studied by spectrophotometric and potentiometric methods with NaClO4 as the supporting electrolyte at I = 0.1 and T = 20 ± 2°C. The molar and protic composition and the pH regions of existence of the complexes were determined, the stability constants of complexes containing the same or different ligands were determined. The fractional distribution of the complexes as the function of acidity was elucidated. The experimental data were treated using mathematical models to estimate the possibility of existence of a broad range of complex species in solution and to distinguish the species that are sufficient to take into account for reproducing the experimental results.