The Polarographic Investigation on the Reaction between Chromium(II)-ethylenediaminetetraacetate and Nitrate Ions

Abstract

Abstract The effect of nitrate ions on the polarographic waves of ethylenediaminetetraacetatoaquochromate(III) ions has been studied in acetate buffer solutions and acid potassium chloride solutions. Nitrate ions are chemically reduced in the vicinity of the mercury drop of the electrode by chromium(II)-EDTA complexes which are formed by the electroreduction of chromium (III)-EDTA complexes. The chromium (III)-EDTA complexes thus formed are reduced again at the DME and the intermediate products of nitrate ions are reduced further chemically with chromium (II)-EDTA complexes or electrochemically, resulting in the enhancement of the current. The nature of the limiting current is investigated and compared with that predicted from the theoretical treatment. The reaction between chromium(II)-EDTA and nitrate ions has also been investigated in acetate buffer solutions and its rate constant, 35 1. mol−1 sec−1 at nearly 0°C, μ=0.1, has been compared with 30 l. mol−1 sec−1, the value obtained from the polarographic catalytic current under almost the same condition.