Borax is the most important compound of boron. When welding metal, people use borax to purify the metal surface. Boric acid is also a commonly used disinfectant in hospitals. Boron is often listed as a rare element abroad. China is rich in borax, so boron is not a rare element in China, but a high-yield element. The chemical formula of borax should be written as Na2B4 O5 (OH) 4 8H2O borax is colorless crystal, which can be dehydrated into anhydrous sodium tetraborate when heated to 400 ~ 500℃ and melted into glass at 878℃. Because the melt contains acid oxide B2O3, the metal oxide can be dissolved. When welding metal, this property can be used to remove oxides on the metal surface. Many metal oxides often show characteristic colors after being dissolved in molten borax, such as cobalt metaborate Co(BO2)2 is blue, nickel metaborate Ni(BO2)2 is brown, and chromium metaborate Cr(BO2)3 is blue-green. Borax has a wide range of uses, which can be used as a filler for washing powder and soap, as well as a raw material for manufacturing optical glass, enamel and porcelain glaze, and can also be used for manufacturing artificial gem and flux. After refining, it can be used to clear heat and detoxify. It is cool and tastes sweet and salty. Can be used for treating sore throat, dental abscess, aphtha, blindness and other diseases. Borax is also commonly used as a metal rust remover, and in agriculture, borax can be used as boron fertilizer. Boron compound borane can also be used as high-energy rocket fuel.