Complex formation between iron(III) and some substituted salicylic acids

Abstract

The complexes formed by salicyluric acid and several substituted derivatives of salicylic acid with ferric ions have been investigated at 25° and in a medium of ionic strength 0·1 using pH and oxidation-potential measurements. The equilibrium constants of complex formation of the 1 : 1 and 1 : 2 mole ratio iron (III)–acid complexes formed are discussed with reference to the inductive, mesomeric, and steric effects of substituents. Appoximate values of the constants for the 1 : 3 complexes of some of the acids were also obtained, and evidence indicating the possible presence of a protonated 1 : 1 complex is reported.