Mass transfer of iodine from n-heptane into the aqueous phase containing potassium iodide and potassium hexacyanoferrate(II) was investigated in a diffusion cell with vibrational agitation. The data obtained were employed to evaluate parameters of the model describing the transfer of iodine accompanied by the formation of triiodide and by oxidation of the hexacyanoferrate(II). The system described is suitable for testing mass-transfer models with a chemical reaction in the liquid-liquid dispersions, since, by a proper choice of concentrations of its reaction components, mass-transfer resistances in individual phases can be varied in a wide range and high sensitivity of parameters of the model can be achieved.