Rates of mass transfer between the bottom of a rectangular agitated vessel and a solution were studied by measuring the limiting current of the cathodic deposition of copper from acidified CuSO4 . Variables studied were rotation speed of a 45degrees pitched blade turbine impeller, physical properties of the solution, equivalent diameter of the vessel base area (de), distance between the impeller and the bottom of the vessel (L), and the presence of the drag-reducing polymer in the solution (Polyox WSR-301). The data were correlated for polymer-free solution by the equation Sh=1.188 Sc-0.33 Re(0.5 ()de/L)(0.32) Polyox addition was found to reduce the mass transfer coefficient by an amount ranging from 24.2 to 56.6% depending on Re and polymer concentration. Practical implications of the present work for the design and operation of dialyzers and electrochemical and heterogeneous catalytic and biochemical reactors are highlighted. Also, the importance of the present work in predicting the rate of diffusion-controlled processes that may take place inside the agitated vessel such as corrosion, electroless plating (chemical plating), and electroplating is discussed.