Sulfite is generally used as an inhibitor, including sodium sulfite, sulfur dioxide, sulfite and so on. Sodium sulfite and sulfur dioxide, though weaker than sodium cyanide, are less toxic, easily oxidized by air, and wastewater is easy to be treated. When sodium sulfite or sulfite is used as an inhibitor for gold, silver and other precious metals, the precious metals will not be lost. Minerals that are inhibited by sodium sulfite or sulphuric acid are easily activated by copper sulphate. Sodium sulfite and sulfite are effective inhibitors of sphalerite and pyrite, but they can activate chalcopyrite instead of inhibiting chalcopyrite. Generally used in weak acid conditions. Sodium thiosulfate and sodium pyrosulfite can be used instead of sodium sulfite or sulfite to inhibit sphalerite and pyrite. Sulfite in pulp is prone to oxidation failure, in order to stabilize the process, the solution needs to be disposed on the day of use, and usually the method of adding in stages.