- Lime (mineral)
Lime is a general term for various naturally occurring
minerals and materials derived from them, in which carbonates, oxides and hydroxides of calciumpredominate. It is also name for single mineral (native lime) of the CaO composition, occurring very rarely. The word 'lime' originates with its earliest use as building mortar and has the the sense of 'sticking or adhering'. [http://www.etymonline.com/index.php?term=lime]
These materials are still used in large quantities as building and engineering materials (including
limestoneproducts, concreteand mortar) and as chemicalfeedstocks, among other uses. Lime industries and the use of many of the resulting products date from prehistoricperiods in both the Old Worldand the New World.
The rocks and minerals from which these materials are derived, typically
limestoneor chalk, are composed primarily of calcium carbonate. They may be cut, crushed or pulverized and chemically altered. "Burning" ( calcination) converts them into the highly causticmaterial "quicklime" ( calcium oxide, CaO) and, through subsequent addition of water, into the less caustic(but still strongly alkaline) "slaked lime" or "hydrated lime" ( calcium hydroxide, Ca(OH)2), the process of which is called "slaking of lime".
When the term is encountered in an agricultural context, it probably refers to
agricultural lime. Otherwise it most commonly means slaked lime, as the more dangerous form is usually described more specifically as quicklimeor "burnt lime".
Lime production process
* Limestone is extracted from quarries or mines.
* Part of the extracted stone, selected according to its chemical composition and granulometry, is calcinated at about 1000°C in different types of kiln, fired by such fuels as natural gas, coal, fuel oil, lignite, etc.
Quicklime is produced according to the reaction: CaCO3 + heat --> CaO + CO2
* Quicklime can be hydrated, i.e. combined with water.
Hydrated lime is produced according to the reaction: CaO + H2O --> Ca(OH)2
* [http://www.carmeuse.com/page.asp?langue=EN&id=12 Lime production process presentation]
calcium oxide, the main component of dry mineral lime.
calcium hydroxide, the hydrated form.
gypsum: a similar mineral.
sascab: a building and paving material ( Central America).
* J.A.H. Oates, Projet de. Lime and Limestone – Chemistry and Technology, Production and Uses. Wiley-VCH, ISBN 3-527-29527-5 (1998)
* [http://minerals.usgs.gov/minerals/pubs/commodity/lime/ US Geological Survey]
* [http://www.lime.org The National Lime Association (US & Canada)]
* [http://www.santacruzpl.org/history/work/limeglos.shtml Glossary by Robert W. Piwarzyk, Santa Cruz Public Libraries, Ca]
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