The use of red copper rods is much wider than that of pure iron, with 50% of copper being electrolytic purified into pure copper every year, which is used in the electrical industry. The red copper mentioned here must be very pure, with a copper content of over 99.95%. A very small amount of impurities, especially phosphorus, arsenic, aluminum, etc., can greatly reduce the conductivity of copper. The oxygen content in copper (which is easily mixed with a small amount of oxygen during copper smelting) has a significant impact on the conductivity, and copper used in the electrical industry generally must be oxygen free. In addition, impurities such as lead, antimony, and bismuth can prevent the crystallization of copper from binding together, resulting in heat embrittlement and affecting the processing of pure copper. This high-purity pure copper is generally refined by electrolysis: impure copper (i.e. crude copper) is used as the anode, pure copper is used as the cathode, and copper sulfate solution is used as the electrolyte. After the current passes, the impure copper on the anode gradually melts, and pure copper gradually precipitates on the cathode. Copper refined in this way; The purity can reach 99.99%.