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{{Chembox new| Name = Calcium oxide| ImageFile = Calcium-oxide-3D-vdW.png| ImageSize = 200px| ImageName = Calcium oxide| IUPACName = Calcium Oxide| Section2 = {{Chembox Properties| Formula = CaO (2845 [kelvin)| BoilingPt = 2850 celsius (3123 kelvin) -->
| Section3 = {{Chembox Structure| Structure = Cubic (crystal system) -->
-->
Calcium oxide (
CaO), commonly known as
burnt lime,
lime or
quicklime, is a widely used
chemical compound. It is a white,
Caustic (substance) and
alkaline
crystalline solid. As a commercial product lime often also contains
magnesium oxide, silicon oxide and smaller amounts of
aluminium oxide and
iron oxide.
Calcium oxide is usually made by the thermal decomposition of materials such as limestone, that contain calcium carbonate (CaCO3; mineral name:
calcite) in a lime kiln. This is accomplished by heating the material to above 825°
celsius,Merck Index of chemicals and Drugs , 9th ed. monograph 1650 a process called calcination or
lime-burning, to liberate a molecule of carbon dioxide(CO2); leaving CaO. This process is reversible, since once the quicklime product has cooled, it immediately begins to absorb
carbon dioxide from the air, until, after enough time, it is completely converted back to
calcium carbonate. Calcination of limestone is one of the first chemical reactions discovered by man and was known in
prehistory.
Usage
As hydrated or
slaked lime, Ca(OH)2 (mineral name:
portlandite), it is used in mortar (masonry) and
plaster to increase the rate of hardening as well as to improve adhesion.
Hydrated lime is very simple to make as lime is a basic anhydride and reacts vigorously with water. Lime is also used in
glass production and its ability to react with silicates is also used in modern metal production (
steel,
magnesium, aluminium and other metals) industries to remove impurities as slag.
It is also used in water and sewage treatment to reduce
acidity, to soften, as a
flocculation, and to remove phosphates and other impurities; in paper making to dissolve lignin, as a
coagulant, and in
bleaching; in agriculture to improve acidic
soils; and in
pollution control, in gas scrubbers to sulfurize waste gases and to treat many liquid effluents. It has traditionally been used in the burial of bodies in open graves, to hide the smell of decomposition, as well as in forensic science, to reveal fingerprints. It is a refractory and a dehydrating agent and is used to purify
citric acid, glucose,
dyes and as a CO2 absorber. It is also used in
pottery, paints and the food industry. Furthermore, quicklime is used in epidemics, plagues, and disasters to disintegrate bodies in order to help fight the spread of disease. CaO is a key ingredient in the
nixtamalization process used to create
maize hominy and masa or tortilla dough.
A relatively inexpensive substance, CaO produces heat
energy by the formation of the hydrate, as in the following equation:US Patent 3,955,554,
Solar heating system.
:CaO + H2O ↔ Ca(OH)2 + 488 BTU/lb of CaO
The hydrate can be reconverted to calcium oxide by removing the water in the reversible equation. If the hydrated lime is heated to redness, the CaO will be regenerated to reverse the reaction. As it hydrates, an exothermic reaction results. One pound of water combines with approximately 3 1/9 pounds of calcium oxide to give calcium hydroxide plus 1618
British thermal unit's of energy. This process can be used to provide a convenient portable source of heat, as for on-the-spot food warming in a
self-heating can.
World lime annual production is around 130 million tonnes, with the USA and China the largest producers, each producing around 20 million tonnes.
See also
External links
- An authoritative discussion of lime and its uses (US context) by the US Geological Survey
- Factors Affecting the Quality of Quicklime
- American Scientist (discussion of C14 dating of mortar)
References
{{Chembox new| Name = Calcium oxide| ImageFile = Calcium-oxide-3D-vdW.png| ImageSize = 200px| ImageName = Calcium oxide| IUPACName = Calcium Oxide| Section2 = {{Chembox Properties| Formula =
CaO (2845 [kelvin)| BoilingPt = 2850 celsius (3123 kelvin) -->
| Section3 = {{Chembox Structure| Structure = Cubic (crystal system) -->
-->
Calcium oxide (
CaO), commonly known as
burnt lime,
lime or
quicklime, is a widely used
chemical compound. It is a white,
Caustic (substance) and alkaline crystalline solid. As a commercial product lime often also contains
magnesium oxide, silicon oxide and smaller amounts of aluminium oxide and iron oxide.
Calcium oxide is usually made by the thermal decomposition of materials such as
limestone, that contain
calcium carbonate (CaCO3; mineral name:
calcite) in a
lime kiln. This is accomplished by heating the material to above 825°
celsius,Merck Index of chemicals and Drugs , 9th ed. monograph 1650 a process called
calcination or
lime-burning, to liberate a molecule of carbon dioxide(CO2); leaving CaO. This process is reversible, since once the quicklime product has cooled, it immediately begins to absorb carbon dioxide from the air, until, after enough time, it is completely converted back to calcium carbonate. Calcination of limestone is one of the first chemical reactions discovered by man and was known in
prehistory.
Usage
As hydrated or slaked lime, Ca(OH)2 (mineral name: portlandite), it is used in
mortar (masonry) and plaster to increase the rate of hardening as well as to improve adhesion. Hydrated lime is very simple to make as lime is a basic
anhydride and reacts vigorously with water. Lime is also used in
glass production and its ability to react with silicates is also used in modern metal production (steel,
magnesium, aluminium and other metals) industries to remove impurities as
slag.
It is also used in water and sewage treatment to reduce acidity, to soften, as a
flocculation, and to remove phosphates and other impurities; in paper making to dissolve
lignin, as a
coagulant, and in bleaching; in agriculture to improve acidic soils; and in pollution control, in gas scrubbers to
sulfurize waste gases and to treat many liquid effluents. It has traditionally been used in the burial of bodies in open graves, to hide the smell of decomposition, as well as in forensic science, to reveal fingerprints. It is a refractory and a dehydrating agent and is used to purify citric acid,
glucose,
dyes and as a CO2 absorber. It is also used in
pottery,
paints and the food industry. Furthermore, quicklime is used in epidemics, plagues, and disasters to disintegrate bodies in order to help fight the spread of disease. CaO is a key ingredient in the
nixtamalization process used to create
maize hominy and
masa or tortilla dough.
A relatively inexpensive substance, CaO produces heat
energy by the formation of the hydrate, as in the following equation:US Patent 3,955,554,
Solar heating system.
:CaO + H2O ↔ Ca(OH)2 + 488 BTU/lb of CaO
The hydrate can be reconverted to calcium oxide by removing the water in the reversible equation. If the hydrated lime is heated to redness, the CaO will be regenerated to reverse the reaction. As it hydrates, an exothermic reaction results. One pound of water combines with approximately 3 1/9 pounds of calcium oxide to give calcium hydroxide plus 1618 British thermal unit's of energy. This process can be used to provide a convenient portable source of heat, as for on-the-spot food warming in a self-heating can.
World lime annual production is around 130 million tonnes, with the USA and China the largest producers, each producing around 20 million tonnes.
See also
- Calcium hydroxide
- Common chemicals
- Limelight
- Magnesium oxide
External links
- An authoritative discussion of lime and its uses (US context) by the US Geological Survey
- Factors Affecting the Quality of Quicklime
- American Scientist (discussion of C14 dating of mortar)
References
Calcium oxide - Wikipedia, the free encyclopedia
Calcium oxide (CaO), commonly known as burnt lime, lime or quicklime, is a widely used chemical compound. It is a white, caustic and alkaline crystalline solid.
Chemical Safety Data: Calcium oxide
Chemical Safety Data: Calcium oxide ... Common synonyms: Quicklime, burnt lime: Formula: CaO: Physical properties: Form: White to light grey powdery solid
Safety (MSDS) data for calcium oxide
Safety (MSDS) data for calcium oxide. Safety data for calcium oxide. Click here for data on calcium oxide in student-friendly format, from the HSci project
CALCIUM OXIDE
1. Product Identification Synonyms: Lime unslaked; lime burnt; quicklime; calx; lime purified CAS No.: 1305-78-8 Molecular Weight: 56.08
Definition: calcium oxide from Online Medical Dictionary
The Online Medical Dictionary is a searchable dictionary of definitions from medicine, science and technology.
calcium oxide definition of calcium oxide in the Free Online ...
Encyclopedia article about calcium oxide. Information about calcium oxide in the Columbia Encyclopedia, Computer Desktop Encyclopedia, computing dictionary.
Chemical of the Week -- Lime
LIME: CALCIUM OXIDE -- CaO. Calcium oxide is a white crystalline solid with a melting point of 2572°C. It is manufactured by heating limestone, coral, sea shells, or chalk, which ...
calcium oxide - Hutchinson encyclopedia article about calcium oxide
Hutchinson encyclopedia article about calcium oxide. calcium oxide. Information about calcium oxide in the Hutchinson encyclopedia.
Calcium Oxide That I Use
calcium oxide - What does CAO stand for? Acronyms and abbreviations by ...
What does CAO stand for? Definition of calcium oxide in the list of acronyms and abbreviations provided by the Free Online Dictionary and Thesaurus.
