The Effect of Chloride Ions on Copper Deposition

Addition of chloride ions to an acidified copper sulfate solution had no effect on the electrode processes below a definite minimum concentration, corresponding to the precipitation of cuprous chloride. The latter was adsorbed by the deposit and acted as a mild addition agent, decreasing the grain size with a corresponding increase in hardness and reflectivity of the deposit, and a small increase in polarization. Increased powder formation and, at high chloride concentration, formation of cuprous chloride were noted at the anode. The general behavior was not affected by the addition of bindarine to the electrolyte, but gelatin considerably increased the powder formation, the latter being maximal at given chloride and gelatin concentrations, and prevented the chloride from entering the deposit, presumably due to the formation of a gelatin‐cuprous chloride complex.