Calcium Oxide

Calcium oxide, commonly known as quicklime or burnt lime, is a white, caustic, alkaline, crystalline solid. Calcium oxide is usually made by the thermal decomposition of materials containing calcium carbonate (e.g. limestone). By heating the material to above 825 °C a process called calcination or lime-burning, to liberate a molecule of carbon dioxide (CO2), is accomplished leaving quicklime. The quicklime is not stable and, when cooled, will spontaneously react with CO2 from the air, to Calcium Carbonate. In water Calcium oxide reacts to form Calcium Hydroxide.


Molar Weight56.077 g/mol
Melting Point2,613°C
Boiling Point2,850°C
Density3.34 g/cm³
FormsWhite, Crystalline, Solid

Uses and Applications

Key applications

  • Wastewater treatment
  • Pulp and paper
  • Building & Construction products


  • Pulp & Paper
  • Coatings & Construction
  • Polymers
  • Mining
  • Water Treatment
  • Food
  • Chemical Processing

Synonyms: Quicklime, Burnt lime, Unslaked lime, E529

Chemical Formula: CaO

CAS Number: 1305-78-8