calcium oxide

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calcium oxide,

chemical compound, CaO, a colorless, cubic crystalline or white amorphous substance. It is also called lime, quicklime, or caustic lime, but commercial lime often contains impurities, e.g., silica, iron, alumina, and magnesia. It is prepared by heating calcium carbonatecalcium carbonate,
CaCO3, white chemical compound that is the most common nonsiliceous mineral. It occurs in two crystal forms: calcite, which is hexagonal, and aragonite, which is rhombohedral.
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 (e.g., limestonelimestone,
sedimentary rock wholly or in large part composed of calcium carbonate. It is ordinarily white but may be colored by impurities, iron oxide making it brown, yellow, or red and carbon making it blue, black, or gray. The texture varies from coarse to fine.
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) in a special lime kiln to about 500°C; to 600°C;, decomposing it into the oxide and carbon dioxide. Calcium oxide is widely used in industry, e.g., in making porcelain and glass; in purifying sugar; in preparing bleaching powderbleaching powder,
white or nearly white powder that is usually a mixture of calcium chloride hypochlorite, CaCl(OCl); calcium hypochlorite, Ca(OCl)2; and calcium chloride, CaCl2.
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, calcium carbide, and calcium cyanamide; in water softeners; and in mortars and cements. In agriculture it is used for treating acidic soils (limingliming
, application to the soil of calcium in various forms, generally as ground limestone, but also as marl, chalk, shells, or hydrated lime. Lime benefits soil by neutralizing acidity, improving texture, and increasing the activity of soil microorganisms.
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). It is incandescent when heated to high temperatures; the Drummond light, or limelight, provides a brilliant white light by heating a cylinder of lime with the flame of an oxyhydrogen torch. Calcium oxide is a basic anhydride, reacting with water to form calcium hydroxidecalcium hydroxide,
Ca(OH)2, colorless crystal or white powder. It is prepared by reacting calcium oxide (lime) with water, a process called slaking, and is also known as hydrated lime or slaked lime. When heated above 580°C; it dehydrates, forming the oxide.
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; during the reaction (slaking) much heat is given off and the solid nearly doubles its volume.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Calcium Oxide


(also quicklime), CaO, a compound of calcium and oxygen; colorless crystals with a density of 3.4 g/cm3 and a melting point of 2585°C. The industrial product is a white porous substance. Calcium oxide reacts vigorously with water, liberating a considerable amount of heat and forming calcium hydroxide: CaO + H2O = Ca(OH)2 (slaking process). Calcium oxide is obtained by the calcination of limestone or chalk. It is widely used in construction, the chemical industry, metallurgy, agriculture, and water purification.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

calcium oxide

[′kal·se·əm ′äk‚sīd]
(inorganic chemistry)
CaO A caustic white solid sparingly soluble in water; the commercial form is prepared by roasting calcium carbonate limestone in kilns until all the carbon dioxide is driven off; used as a refractory, in pulp and paper manufacture, and as a flux in manufacture of steel. Also known as burnt lime; calx; caustic lime.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


A white or grayish-white caustic substance, calcium oxide, usually obtained by heating limestone or marble at a high temperature; used chiefly in plasters, mortars, and cements. In the past, in many areas along the seacoast where limestone was scarce, seashells were heated to obtain lime. See also hydrated lime, hydraulic lime, mortar, shell lime, slaked lime.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

calcium oxide

a white crystalline base used in the production of calcium hydroxide and bleaching powder and in the manufacture of glass, paper, and steel. Formula: CaO
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
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The effectiveness and sustainability of Cao Tieu Tri An Tri Nam has made it indispensable for the treatment of hemorrhoids.
Cao, meanwhile, acknowledged her husband's role in her professional development, saying he pushed her to keep working on her doctorate degree in biology when she felt like giving up.
'All goods of foreign origin imported into the Philippines or their containers, shall be conspicuously marked in any official language of the Philippines as legibly, indelibly and permanently as the nature of the goods or container will permit and in such a manner as to indicate to an ultimate purchaser or end-user or consumer in the Philippines the name of the country of origin of the goods,' the CAO read.
When Cao Cao was released temporarily to breed with a wild male, a team of panda trainers and keepers followed her closely, checking for signs of injury or hunger.
Cao also used data on tuition from the Integrated Postsecondary Education Data System (IPEDS), a federal database for higher education information, and cross-referenced that with New York's tuition assistance program.
Performers wear black and white costumes with angled details and Cao Cao and his soldiers wear elements of red to distinguish themselves.
No calcium oxide was observed because a decomposition of CaC[O.sub.3] to CaO occurs at temperature higher than 600[degrees]C [12].
CHINA CHAMPIONSHIP Eurosport 1, from 7.30am RYAN DAY has been a man to follow this season and tends to perform well in China, but at the prices it could be worth punters trying to find a way to support home player Cao Yupeng against the Welsh ace, writes Adrian Humphries.
Alan Gormley, Chief Analytics Officer, Mobacar who will be speaking at the event, stated about the evolving role of the CAO in a recent interview with Corinium:
[10] produced biodiesel from palm oil using CaO catalyst which synthesized various seashells that include mussel, cockle, and scallop and reported surface areas ([S.sub.BET]) of 89.91 [m.sup.2]/g, 59.87 [m.sup.2]/g, and 74.96 [m.sup.2]/g, respectively.