A chemical compound with the formula CaO which is a whitish, odorless solid that does not dissolve well in water. It will, however, react with water (H20) to form calcium hydroxide (CaOH, a base). It has a melting point of 2614 degrees Celsius and a boiling point of 2850 degrees Celsius. It can be made by heating calcium carbonate (CaCO3, limestone) until carbon dioxide (CO2) is released. It has a great many industrial uses.