Electrolytic copper can be further processed into extremely fine electrolytic copper powder. The principle of copper electrorefining is as follows: Anode reactions: Cu — 2e - = Cu 2+; Me — 2e - = Me 2+; H 2 O — 2e - = 2H + + 1/2O 2; SO 4 2- — 2e - = SO 3 + 1/2O 2. Here Me represents metals that are more electronegative than copper, such as Fe, Ni, Pb, As, and Sb, which dissolve from the anode into the solution. The reactions in which H 2 O and SO 4 2- lose electrons have more positive potentials than copper, so they do not occur under normal conditions. Precious metals have even more positive potentials, so they do not dissolve and instead enter the anode slime. Cathode reactions: Cu 2+ + 2e = Cu; 2H + + 2e - = H 2; Me 2+ + 2e - = Me. Among these reactions, only metal ions with a standard potential more positive than that of copper and with sufficiently high concentration can be reduced at the cathode; however, since they do not dissolve at the anode, the reduction of copper ions is the main cathode reaction.