Calcium Oxide

Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature. The broadly used term lime connotes calcium-containing inorganic materials, which include carbonates, oxides and hydroxides of calcium, silicon, magnesium, aluminium, and iron predominate, such as limestone. By contrast, quicklime specifically applies to a single chemical compound.

Quicklime is relatively inexpensive. Both it and a chemical derivative (calcium hydroxide) are important commodity chemicals.