Iron redox reactions hexacyanoferrates

V. Marecek, Z. Samec, and J. Weber, The Dependence of the Electrochemical Charge-Transfer Coefficient on the Electrode Potential. Study of the Hexacyanoferrate (III) Hexacyanferrate (IV) Redox Reaction on Polycrystalline Gold Electrode in Potassium Fluoride Solutions, J. Electroanal. Chem. Interfacial Electrochem. 94, 169-185 (1978) cf. also J. Weber, Z. Samec, and V. Marecek, The Effect of Anion Adsorption on the Kinetics of the Iron (3 + )/Iron (2. ) Reaction on Platinum and Gold Electrodes in Perchloric Acid, J. Electroanal. Chem. Interfacial Electrochem. 89, 271-288 (1978). 

Three further papers have appeared on the reaction of polyaminocarboxyl-ato-iron(III) complexes with cyanide. In all cases the reaction sequence involves a final redox step, in which liberated ligand reduces intermediate cyano-iron(III) species to hexacyanoferrate(II). The ligands involved are N-(2-hydroxyethyl)iminodiacetate, triethylenetetraminehexaacetate, and 2-hydroxytrimethylenediaminetetraacetate both in mononuclear and in binuclear complexes. 

An example of a transfer function based on a physical model is the Nemst impedance of a transport controlled electrode reaction. The impedance spectra in Fig. 7-14, which were obtained on a rotating platinum disk electrode at the equilibrium potential of the iron hexacyanoferrate redox system, exhibit the typical shape of a transport-controlled process. The transfer function cannot be described by a limited number of electrical circuit elements but must be derived from the differential equations of Fick s 2nd law and the appropriate boundary conditions. For finite linear diffusion, the so-called Nemst impedance Z can be derived theoretically... 

---