Kinetics of the alizarine red S surface redox reaction

Kinetics of the surface redox reaction of alizarine red S adsorbed on mercury is measured by square-wave voltammetry. In 1 mol/l KNO3 buffered to pH 9.22, the standard reaction rate constant of the redox couple anthraquinone/anthrahydroquinone in the adsorbed alizarine red S molecule is k(s) = 100 +/- 10 s(-1) and the cathodic transfer coefficient is alpha = 0.4. At pH 2 in this medium k(s) is greater than 500 s(-1).