CaO – calcium oxide – is a white, caustic, crystalline substance that yields a strong alkali Ca(OH)2 in water and is capable of corroding organic tissues. It is also known as quicklime or burnt lime. Quicklime is usually obtained by roasting limestone in a furnace at about 1000 °C. This compound is useful in many processes. For instance, it is used in water and sewage treatment to reduce acidity and to remove phosphates and other impurities. It is also used in gas scrubbers to desulfurize waste gases as part of pollution control efforts. In agriculture, it can be used to improve acidic soil. It is also used in the production of concrete and paints, and as an acidity regulator in food.