Complex formation of nickel(II) ions with citric acid in aqueous solution: a potentiometric and spectroscopic study

Abstract

From a potentiometric and visible spectrophotometric study of the nickel(II)-citric acid (H₃L) system in the pH range 3-6, four complexes, NiL^-, NiHL, NiH₂L⁺ and NiL₂^4-, have been characterized. Stability constants for the formation of these complexes have been determined at 25°C in 0.1 mol dm^-3 KCl. The results suggest that the hydroxy group of citric acid is coordinated in the nickel-citrate complexes.