Interaction of Iron(III) with 2-Hydroxybenzoic Acid in Aqueous Solutions

The complex formation between the Fe(3+) ion and 2-hydroxybenzoic acid (salicylic acid, H(2)L) has been studied at 298.15 K in 1.05 mol.kg(-1) NaClO(4) medium by both potentiometric titrations with glass electrodes and spectrophotometric measurements in the range of wavelengths between (410 and 600) nm. The concentrations of ligand (C(L)) and metal ion (C(M)) were varied between (0.105 x 10(-3) x 21 x 10(-3)) mol.kg(-1), and the ligand-to-metal ratio was varied between (1 and 1000) (1 <= C(L)/C(M) <= 1000). The hydrogen ion concentration was decreased stepwise to the incipient precipitation of a basic salt of metal. The experimental data have been explained with the formation of the complexes FeL(+), FeL(2)(-), FeL(3)(3-), Fe(HL)L, and Fe(2)(OH)(2)(HL)L(+). Stability constants for their formation in 1.05 mol.kg(-1) NaClO(4) as well as in dilute solution are reported. OI sindona, giovanni/0000-0002-5623-5795