Extraction, complex formation and spectrophotometric determination of iron(III) with 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone

Abstract

The extraction of iron(III) from aqueous HCl, H2SO4, HClO4, HNO3 solutions by 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone (HA) dissolved in CHCl3 has been studied. Quantitative extraction of iron(III) is achieved if the concentration of the acids does not exceed 1N. The composition of the iron (III)—HA complex formed in the organic phase was investigated spectrophotometrically, radiometrically and by analysis of the isolated species. In the aqueous phase iron (III) and HA form three different complexes, depending on the initial iron: HA concentration ratio and the pH of the solution. They are the violet FeA2+, the orange-red FeA2 + and the orange-yellow FeA3. The latter is identical with the complex found in the organic phase, which was isolated as a solid crystalline material and characterized by elemental analysis and infrared spectroscopy. A spectrophotometric method for the determination of iron(III) in the aqueous phase and in the chloroform solution, by extraction with HA, is described.