Electrolytic Refining

Electrolytic refining is a purification technique that uses an electric current passed through a chemical bath to dissolve an impure slab of metal, cast as the anode, and redeposit the metal in a much purer form onto a thin starter sheet acting as the cathode, while less noble impurities stay dissolved in the solution or fall away as an anode sludge. The English metallurgist James Elkington patented the technique for refining copper in 1865, and it was adopted commercially soon after, since electrolytic copper's very high purity is essential for electrical wiring, which base blister copper cannot supply on its own. The process was later extended to refining other metals including nickel and gold, and the anode sludge from copper electrorefining became commercially important in its own right, since it concentrates the silver, gold and other precious metals the original copper ore carried.