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 =0.4. At pH 2 in this medium k_s is greater than 500 s^-1.