Quick lime (CaO) is calcium oxide. It is prepared on a large scale by burning lime stone and fuel in vertical kilns at 1073 K. Air is passed from the bottom of the tower to sweep away carbon dioxide which is formed during the process.
CaCO3 CaO + CO2
The simultaneous removal of carbon dioxide prevents the backward reaction. Since silica is present as impurity in limestone, temperature should be kept very high otherwise fusible silicates will result.
- Calcium oxide is a white amorphous solid.
- It melts at 2870 K
- On exposure to air, it absorbs moisture and carbon dioxide to form a mixture of calcium hydroxide and calcium carbonate
- Manufacture of building material like cement.
- Purification of sugar process.
- Softening of hard water process.
- Drying of gases and alcohol.
- Manufacture of fertilisers, germicides and disinfectants.