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Calcium oxide

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Calcium oxide
Systematic name Calcium Oxide
Other names Quicklime; lime; calx
Molecular formula CaO
Molar mass Molar mass::56.08 g/mol
Appearance white solid
CAS number CAS number::1305-78-8
Density and phase [[Density::3.34 g/cm3, solid]]
Solubility in water 0.189 g/100 ml (0°C)
Melting point Melting point::2572°C
Boiling point Boiling point::2850°C
Crystal structure Rhombohedral
MSDS Calcium Oxide Safety Data Sheet
Main hazards corrosive
NFPA 704

NFPA 704 svg.png

Flash point non-flammable
R/S statement R: 34
S: 26-36/37/39-45
RTECS number EW3100000
Related compounds
Other anions Calcium sulfide Calcium hydroxide
Other cations

Beryllium oxide
Magnesium oxide
Strontium oxide
Barium oxide

Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Disclaimer and references

Calcium oxide, or quicklime, has been used by man for centuries. It is cheap to make and is used in the production of a variety of products. It is not found naturally in nature, but is produced through the burning of calcium carbonate. It is one of the most used substances in America even though it is highly reactive in pure form.[1]


Calcium Oxide exists as a odorless crystalline solid. In its pure form it can be found as a white crystal or a white powder. It can also take the form of gray or white colored lumps.[2] It has an extremely high boiling point at 2572°C. Around this temperature the lime becomes incandescent and gives off a strong light. [1] The substance is corrosive but not flammable.[3]

Quicklime can react with several substances including water, glycerol, sugars, and acids. When calcium oxide is combined with water it produces a violent reaction that can reach 800°C. [3] This reaction then results in the formation of calcium hydroxide (CaH2) or slaked lime. It will also react with carbon dioxide to produce calcium carbonate.[2] Calcium oxide also reacts with acids to make calcium salts and with acidic oxides to produce silicates and phosphates. [4] Lime can also react with sodium carbonate and silica sand to produce an amorphous glass-like substance and other silicates to produce various substances.[1]


20-year-old calcium oxide, doesn't react with water
Due to its reaction with water and carbon dioxide, calcium oxide is not found naturally.[2] However, this does not mean that it is a rare substance. Quick lime has been manufactured for longer than human history records and is one of the oldest chemically produced substances by man.[1] Its origins have been traced through time to the civilizations of Rome, Greece, and Egypt.[4] Even today it is produced on a massive scale. Out of the U.S. alone 22 million tons were manufactured in the year 2000.[1]

The production of calcium oxide is a simple and easy process. Calcium carbonate is first heated from 500-600°C. This causes the intramolecular bonds to weaken. This reaction causes calcium carbonate to split and results in the chemicals calcium oxide and carbon dioxide. However, since calcium oxide reacts with carbon dioxide, the calcium dioxide needs to be pumped away from the calcium oxide during the reaction. The entire process appears like this: CaCO3(s)--> CaO(s) + CO2(g)[1]


Calcium oxide has many different uses and is used widely today. The compound is essential in construction work since it is a central ingredient in high grade steel, cement, mortar, and plaster. It is also used in the manufacture of rubber, soap, varnish, and refractories as well as medicinal products, insect killers, and plant and animal food. It is used in agriculture as a way of improving the quality of the soil. As stated earlier, it is a ingredient in some silicate glass products, and it is used in the production of calcium carbide, basic calcium nitrate and calcium bisulphite. It is also used in de-hairing animal hides. [1] [4]

Lime has had one other use in theater. Before electric lighting was invented, lime would be heated to a very high temperature until it gave off a bright incandescent glow. These were used as stage lights and it is the source of the stage term - "lime light".[1]

Affects to Health

Any contact with Calcium oxide is very dangerous. It will cause blistering and inflammation when in contact with the skin, and can cause corneal damage or blindness if it makes contact with the eyes. If swallowed or inhaled it can cause irritation in the respiratory tract and gastrointestinal tract. This is typically characterized by burning sneezing and coughing and over exposure can result in choking, lung damage, unconsciousness, or death. The amount of damage depends on the length of exposure.


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 LIME: CALCIUM OXIDE — CaO Prof. Shakhashiri,, accessed 2/3/11
  2. 2.0 2.1 2.2 Calcium Oxide Net Industries , Accessed 2/3/11.
  3. 3.0 3.1 Material Safety Data Sheet calcium oxide MSDS, 11/01/2010
  4. 4.0 4.1 4.2 Calcium Oxide (CaO), accessed 2/3/11