Extremely pure copper (greater than 99.95%), called electrolytic copper, can be made by electrolysis. The high purity is needed because most copper is
used to make electrical equipment, and small amounts of impurity metals in copper can seriously reduce its ability to conduct electricity. Even 0.05%
of arsenic impurity in copper, for example, will reduce its conductivity by 15%. Electric wires must therefore be made of very pure copper, especially
if the electricity is to be carried for many miles through high-voltage transmission lines. |