Calcium oxide, commonly known as lime, is a chemical compound with the formula CaO. Calcium oxide, also known as quicklime, is an alkaline substance that has been in use since the medieval age. It is believed that quicklime is one of the oldest chemicals known to the human race.
Calcium oxide is widely used in industry, e.g., in making porcelain and glass; in purifying sugar; in preparing bleaching powder, calcium carbide, and calcium cyanamide; in water softeners; and in mortars and cements. In agriculture it is used for treating acidic soils (liming).