Molten copper containing variable quantities of oxygen up to the saturation concentration 0.8 wt % O can be effectively deoxidized by calcium chloride melts containing 5 wt % calcium carbide. Cyclic voltammetry, on solid copper electrodes in this melt at a temperature of 1073 K, revealed the reaction responsible for copper deoxidation, namely, the electrochemical oxidation of the carbide ion C-2(2-).