Calcium oxide
Calcium oxide CaO, is a chemical compound of calcium and oxygen. It is also known as lime or quicklime, a white or grayish white solid produced in large quantities through the roasting of calcium carbonate so as to drive off carbon dioxide (calcination). At room temperature, CaO will spontaneously absorb carbon dioxide from the atmosphere, reversing the reaction, and absorb water, converting itself into calcium hydroxide and releasing heat. It is called quick or living lime because of the bubbling that occurs during the reaction.
The phrase limelight comes from its use as stage lighting, as when heated to incandescence in an oxyhydrogen flame -a brilliant white light is emitted. It is also sometimes used directly as a fertilizer but is best-known as an alternative to cementitious based mortars, renders and bases.
In large amounts it is used to produce calcium carbide, CaC2 or carbide, (calcium acetylide). This compound decomposes in water, forming acetylene gas which is flammable and calcium hydroxide, Ca(OH)2. It can be used to produce acetylene fuel for welding and it can be used for carbide lamps, such as those used lighthouses. Calcium carbide also is used to make calcium cyanamide, CaCN2, a fertilizer component and starting material for certain plastic resins.
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