Potentiometric determination of the standard potential of the As(V)/As(III) couple

The potential of the couple As(V)/As(III) was measured at 25 degrees cent. with a glass electrode as reference electrode in order to eliminate the liquid junction potential. The presence of iodide is required in order to increase the rate of the electron exchange between arsenic at the two oxidation states. A standard potential of 573 mV was determined for the reduction of the hydroxylated species