ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Photometric microtitration of iron by using 7-(o-carboxyphenylazo)-8-hydroxyquinoline-5-sulfonic acid

J. Chýlková and V. Říha

Department of Environment of Chemical Industry, Institute of Chemical Technology, CS-532 10 Pardubice

Abstract: The complex-forming equilibria of 7-(o-carboxyphenylazo)-8-hydroxyquinoline-5-sulfonic acid (indicator OKFAZOX) with Fe(III) ions were inves­tigated by spectrophotometric methods in the pH range 1.5—3. It has been found that OKFAZOX forms with Fe(III) complexes in the stoichiometric ratio c_Fe: c_ind = 1 1 with conditional stability constant log ß_re(ind) = 5.60 ± 0.02 id and in the stoichiometric ratio c_Fe : c_ind = 1 2 with conditional stability constant log  ß_re(ind)2= 10.50 + 0.05 (pH = 2.56, í = 0.1 mol dm^-3 ). The indicator OKFAZOX is suited to chelatometric determination of iron with photometric indication. Provided the titration is carried out at pH = 3 and Cn = 8 x 10^-6 mol dm^-3 and is photometrically observed at the wavelength of id 510 nm, it gives correct and accurate results. The method is also applicable in the region of micromolar concentrations. The presence of AI, Cr, Mn, and Zn does not interfere. The interfering effect of Cu and Pb may be eliminated by reducing the pH value during determination to ≈ 1.7 . The developed method was applied to practical samples of drinking and utility water.

Full paper in Portable Document Format: 385a607.pdf

Chemical Papers 38 (5) 607–617 (1984)