# Calcium oxide, CaO

Calcium oxide (CaO), commonly known as quicklime, is a widely used inorganic compound with a cubic crystal structure. It is a basic oxide with strong alkaline properties and is notable for its high melting point and thermal stability. In the field of optics, CaO is generally not used in its pure form but serves as an important component in various types of glass, including soda-lime glass and borosilicate glass. It acts as a stabilizer and helps in improving the chemical durability of the glass. Beyond optics, calcium oxide is extensively used in the production of cement, as an alkaline agent in chemical processes, and in flue-gas desulfurization. It is prepared on an industrial scale by the calcination of limestone, which drives off carbon dioxide, leaving behind calcium oxide. Its high reactivity with water—forming calcium hydroxide and releasing significant heat—requires careful handling. Overall, calcium oxide is a versatile material with applications extending beyond optics into construction, chemistry, and environmental engineering.

## Other names

- Lime
- Quicklime
- Burnt lime
- Unslaked lime
- Free lime
- Caustic lime
- Pebble lime
- Calcia
- Oxide of calcium

## Mineral

- Lime

## External links

- Calcium oxide - Wikipedia
- Calcium oxide - NIST Chemistry WebBook
- Calcium oxide - WebElements