Amperometric titration with the convection electrode I

Studies on analysis with the Convection electrodes V

Abstract

The convection electrode, which has already been reported by the author in Nippon Kagaku Zasshi, 81, 98 (1960); 82, 46 (1961), is applied to the amperometric titration. It is constructed as follows. An aluminum disk of a pulley-shape coated with paraffine wax is rotated horizontally at a constant rate (3600rpm) in the titration vessel (electrolytic cell) near the stationary platinum-wire electrode, which is set on the side wall of the cell.
Current-potential curves of Fe²⁺ in 0.1N H₂SO₄ and Ag⁺ in 0.1M KNO₃ are investigated and fairly reproducible waves are obtained. The systems of Cr₂O₇^2--Fe²⁺, S₂O₃^2- -I₂, Cl^--Ag⁺, and Fe(CN)₆^3- -Ag⁺ are studied as the typical reactions, which are unaffected by dissolved oxygen.
10^-6N of Cr₂O₇^2- and S₂O₃^2- can be determined with the error of about 2%, and 10^-4N of Cl^- and Fe(CN)₆^3- with the error of about 3% and 1% respectively. The proposed method is more accurate especially at low concentrations than the ordinary method with a rotating platinum electrode. Ethyl alcohol, instead of acetone previously used by Laitinen et al., is added to the sample solutions at the precipitation reaction to decrease the solubility of precipitates, and good results are obtained.