A recently introduced method for interposing thin layers of organic solvents between graphite electrode surfaces and aqueous solutions was used to examine the effects of the nature and concentration of the supporting electrolytes on electrochemical responses for reactants dissolved in the thin layers of organic solvent. The method was also used to evaluate the rates of electron transfer between coreactants, each of which was confined to one of the two adjoining, immiscible phases. The rates of these electron-transfer reactions were shown not to be influenced by simultaneous cross-phase ion-transfer processes in cases where such processes were forced to proceed. The rates of the electron-transfer reactions exhibited only weak sensitivity to the driving force of the reactions. This insensitivity was tentatively interpreted as an indication that assembly of the reactant pairs into precursor complexes may be the step that limits the rate of the electron-transfer process.