Calcium sulfite is a chemical compound with the formula CaSO₃. It is a white, crystalline solid that is primarily used in various industrial applications, including the production of gypsum and as a reducing agent in the treatment of flue gases. Calcium sulfite can also be found in some food preservation processes. In addition to its industrial uses, calcium sulfite plays a role in environmental management. It is often used in water treatment to remove impurities and can help reduce sulfur dioxide emissions from power plants. Its ability to react with other compounds makes it valuable in both chemical and environmental applications.