The oxidation reactions of hexacyanoferrate(H) and hydroquinone in KCl media were studied on disk platinum electrodes using chronoamperometry under a strong magnetic field (1.74 T). The limiting current measured under magnetic field i(B) can be expressed as a function of parameters that control the mass transfer phenomenon by i(B) = KCa D-b d(c) v(e) epsilon(f) B-g n(h). C represents the electroactive species concentration (mol m(-3)), D the diffusion coefficient of the electroactive species (m(2)s(-1)), d the working electrode diameter, v the kinematic viscosity of the electrolyte (cS), epsilon the dielectric constant of the solution, B the magnetic field strength (T), n the number of electrons involved in the redox process and K is a proportionality constant. Contribution of B to the limiting current is well established (g = 1/3), whereas the contribution of D has to be confirmed (b = 1). The aim of this work was to specify the influence of the other parameters for which various results have been published in recent literature. We concluded that i(B) = KC(4/3)Dd(5/3)v(-2/3)epsilon(-7/4)B(1/3)n, quantifying for the first time, to our knowledge, the drastic influence of the electrolyte dielectric constant. (C) 2004 Elsevier Ltd. All rights reserved.