Kinetic measurements on a stationary disk electrode in a uniformly rotating fluid (SDERF) — I. The limiting diffusion current in the Fe(CN)4−6-Fe(CN)3−6-system

The construction and operation of an electrochemical cell provided with a sde in a uniformly rotating fluid (SDERF-cell) are reported. The test of the SDERF-cell with respect to the diffusional kinetics is made with the Fe(CN)^4?₆-Fe(CN)^3?₆ system in 1 M solutions of NaOH, KCl and KNO₃, in potentiodynamic conditions. The linear relationship between the limiting diffusion current I_d and the square root of the angular velocity of the rotor, ω^{$\text{1}\text{2}$}_r holds, but the straight line does not intercept the coordinate axes in the origin. The square root of the angular velocity of fluid, ω^{$\text{1}\text{2}$}_f — calculated from I_d — depends only on the ω^{$\text{1}\text{2}$}_r — value irrespective of the concentration and the physical properties of the fluid. The diffusion coefficients and the activation energy of diffusion, E_a, in 1 M KNO₃ were measured; E_a = 3.15 kcal/mol for both Fe(CN)^4?₆ and Fe(CN)^3?₆-ions.