Calcium oxide
Calcium oxide is usually made by the thermal decomposition of CaCO3, heating materials such as limestone to around 500°C and so removing the carbon dioxide in a reversible reaction. It is one of the first chemical reactions discovered by man and was known in prehistory: see limekiln.
As hydrated or slaked lime, Ca(OH)2, it was used in mortar and plaster to increase the rate of hardening. Hydrated lime is very simple to make as lime is a basic anhydride and reacts vigorously with water. Lime was also used in glass production and its ability to work with silicates is also used in modern metal production (steel, magnesium, aluminum and other non-ferrous metals) industries to remove impurities as slag.
It is also used in water and sewage treatment to reduce acidity, to soften, as a flocculant and to remove phosphates and other impurities; in paper making to dissolve lignin, as a coagulant and in bleaching; in agriculture to improve acid soils; and in pollution control - in gas scrubbers to desulphurize waste gases and to treat many liquid effluents. It is a refactory and a dehydrating agent and is used to purify citric acid, glucose, dyes and as a CO2 absorber. It is also used in pottery, concrete, paints and the food industry.
Calcium oxide (CaO), commonly known as lime or quicklime, is a widely used chemical compound. It is a white, caustic and alkaline crystalline solid. As a commercial product lime often also contains magnesium oxide, silicon oxide and smaller amounts of aluminium and iron oxides.
General
Name
Calcium oxide
Chemical formula
CaO
Appearance
White solid
Physical
Formula weight
56.1 amu
Melting point
3200 K (2927 °C)
Boiling point
3773 K (3500 °C)
Density
3.3 ×103 kg/m3
Crystal structure
NaCl
Solubility
hydrolysed
Thermochemistry
ΔfH0gas
43.93 kJ/mol
ΔfH0liquid
-557.33 kJ/mol
ΔfH0solid
-635.09 kJ/mol
S0gas, 1 bar
219.71 J/mol·K
S0liquid, 1 bar
62.31 J/mol·K
S0solid
38.19 J/mol·K
Safety
Ingestion
Dangerous—causes GI irritation, larger doses could be fatal.
Inhalation
Dangerous - irritation; chemical bronchitis or even death for larger exposures.
Skin
Irritation and possible burns.
Eyes
May cause permanent damage.
More info
Hazardous Chemical Database (http://ull.chemistry.uakron.edu/erd/chemicals/7/6247.html)
SI units were used where possible. Unless otherwise stated, standard conditions were used.