Mass transfer between gas sparged two immiscible nondispersed liquids was studied by measuring the limiting current of the cathodic reduction of ferricyanide ion at the surface of a mercury pool cathode. Rates of mass transfer were measured for three cases, namely: (i) batch gas sparged reactor; (ii) continuous gas sparged reactor with superimposed solution flow admitted to the reactor from a side entry nozzle located at the mercury surface; (iii) continuous single phase flow reactor (unsparged). Variables studied were N-2 superficial velocity, physical properties of the solution, solution velocity and inlet nozzle diameter (d(n)). The following correlations were obtained for solutions of Sc ranging from 1740 to 6000. Single phase mass transfer data without gas sparging were correlated by the equation: Sh = 0.236Sc(0.33) Re-0.89 (d/dn)(0.68) Gas sparging mass transfer data in a batch reactor were correlated in terms of the mass transfer J factor by the equation: J = 0.39(Re Fr)(-0.16) Mass transfer data obtained for the combined gas sparging and single phase flow were found to fit the equation: Sh = 28 (ScReReg0.28)-Re-0.33-Re-0.24 Implications of the present results for enhancing the rate of diffusion controlled chemical and metallurgical processes between two immiscible nondispersed liquids, and design of electrochemical reactors employing mercury pool cathode are noted. (C) 2004 Elsevier B.V. All rights reserved.