Abstract
The purpose of this investigation was to study the reaction between Fe (III) and ferron (7-iodo-8-hydroxyquinoline-5-sulfonic acid) in an aqueous solution spectrophotometrically and to apply ferron as an indicator to complexometric titration of Fe (III) with EDTA. A green complex which is formed with Fe (III) and ferron has two maxima of absorption at 620 mμ and 450 mμ. The optimum pH is 2.3 to 2.8 and the mole ratio of Fe (III) to ferron is 1 to 3. Its stability constant is 3 × 1027. Titration of Fe (III) using ferron as an indicator is carried out at pH 2.5. In visual titration, the color changes from green to yellow at the end point, and the optimum concentration of Fe (III) is 20 to 70 mg in 100 ml. In photometric titration at 610 mμ, the optimum concentration of Fe (III) is 1 to 20 mg in 50 ml. The procedure was applied to the determination of small amounts of Fe (III) in commercial Mohr's salt.
