“…However, the non-linear change of D with temperature demonstrates that the investigated redox system does not really obey the Stokes-Einstein equation: D = k B T/6prg (where: k B is Boltzmann's constant, r the hydrodynamic radius of the diffusing species, and g the viscosity of solvent medium) [24]. It is, therefore, probable that due to solvation effects, the hydrodynamic radius of the involved redox species is not constant [25]. However, it must be mentioned that the hexacyanoferrate(III) ion, due to its unsymmetrical charge distribution and its higher charge density, is more easily solvated than the more voluminous hexacyanoferrate(II) ion with symmetrical charge distribution [26].…”