THE CATALYTIC OXIDATION OF ASCORBIC ACID BY Cu (Ⅱ)-EDTA CHELATE

The kinetics of catalytic oxidation of ascorbic acid by Cu(Ⅱ)-EDTA chelate has been studied. The catalytic activity of this chelate was found to change with pH. Cu (Ⅱ)-EDTA chelate showed no catalytic activity at pH 8.8, but at pH 3.5, obvious catalytic activity was observed. The catalytic activity was not attributed to the dissociated cupric ions, but to the chelate itself. The concentration of ascorbic acid and intermediate hydrogen peroxide has oscillatory behavior during the oxidation of ascorbic acid at pH 3.5. The main reactions taken place in the system of Cu(Ⅱ)-EDTA-ascorbic acid-O₂ were proposed.