A pH- and Redox-Potentiometric Study of Equilibria between Fe(II), Fe(III), and N-(Carboxymethyl)Aspartic Acid

Complexation in the Fe²⁺–Fe³⁺–N-(carboxymethyl)aspartic acid (H₃L) system in aqueous solutions was studied by pH- and redox-potentiometric titration at 25°C and at an ionic strength of 0.1 (KCl). Depending on the H₃L concentration and pH, neutral, protonated, and hydroxo complexes of iron(III) can be formed in the solutions. The stability constants for all the detected complexes were calculated, and the distribution plots for the fractions of complexes vs. the solution pH were constructed.