Copper rods are more widely used than pure iron. Every year, 50% of copper is electrolytically purified into pure copper for use in the electrical industry. The copper mentioned here must be exceptionally pure, containing more than 99.95% copper. A large number of impurities, especially phosphorus, arsenic and aluminium, will greatly reduce the conductivity of copper. Oxygen content in brass sheet copper (which is easily mixed with large quantities of oxygen in copper smelting) has a great impact on conductivity. As usual, copper used in electrical industry must be oxygen-free copper. In addition, lead, antimony, bismuth and other impurities will make the crystallization of copper can not be combined to form a hot brittle, but also affect the processing of pure copper. White copper plate, a kind of pure copper with high purity, is usually refined by electrolysis: Impure Copper (i.e. crude copper) is used as an anode, pure copper as a cathode, and copper sulfate solution as an electrolyte. When the current is smooth, the Impure Copper on the anode gradually melts, and the pure copper gradually accumulates on the cathode. The purity of copper obtained from white copper strip can reach 99.99%. Purple copper is a kind of copper which is similar to dirty. It can be regarded as pure copper in general. It has good conductivity and plasticity, but its strength and hardness are worse.