The right angle triangular/semicircular cylindrical promoters are inserted at the bottom of a rectangular electrolytic cell and limiting current data are measured at the copper microelectrodes fixed on an electrode support The effects of flow rate of the electrolyte, height/radius of the promoter and spacing between the promoters on mass transfer are investigated. The electrolyte consisted of 0 01 N potassium ferricyanide, 0 01 N potassium ferrocyanide and 0.5 N sodium hydroxide The mass transfer coefficient is increased with the increased height/radius of the promoter Increased spacing between the promoters resulted in lowering of the mass transfer coefficient