Oxidation-reduction potential of the ferro-ferricyanide system in buffer solutions

The redox potential (E0′) of the potassium ferrocyanide-potassium ferricyanide oxidation-reduction potential buffer was measured in four pH buffer solutions, acetate, Tris, phosphate, and borate, under specified conditions of pH, solution composition, and temperature. The potentials reported should be accurate, on the hydrogen electrode scale, to within about 2 mV and precise to within at least ±0.3 mV. Although the potential of the ferro-ferricyanide couple is sensitive to fairly small changes in experimental conditions, several methods are discussed by which this potential can be estimated with a reasonable degree of accuracy (about 2–10 mV) in solutions which differ somewhat from the particular solutions reported here. Attention is called to the need for greater care in specifying experimental conditions in the determination of redox potentials of various biological species.