The effect of different concentrations of 40% (v/v) formalin solution and acetone on the electrowinning and electrorefining of copper from acidified copper sulfate solution under natural convection regime has been studied at different temperatures. The results show that the limiting current density and consequently, the rate of copper electrodeposition decreases with increasing the mole fraction of the co-solvent due to the changes in the physicochemical properties of the mixture like density, viscosity, dielectric constant and state of solvation. The percentage of inhibition in presence of the co-solvent ranged between 3.6 and 45.5% dependent on the type and mole fraction of the co-solvent, temperature and anode type. A criticism to the effect of oxygen discharge velocity on enhancing the electrodeposition process and its relation with the mass transfer coefficient has been recorded. Thermodynamic parameters and electron dispersive X-ray analysis (EDX) of the deposits formed on the cathode surface have been studied to understand the effect of such solvents on the electrodeposition process. (C) 2002 Published by Elsevier Science B.V.