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.
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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
References in periodicals archive ?
4, hydration of calcium oxide CaO is going partially according to reaction CaO + [Ca.sup.2+] + [H.sub.2]O = 2CaO[H.sup.+].
Among the applied alleviating additives, bentonite and calcium oxide (in smaller degree) proved the most effective as regards the number of those bacteria in samples contaminated with petroleum-derived substances, especially with petrol.
Explains Entry, "We already knew, from work others had done, that chemicals like aluminum sulfate and calcium oxide can slow the loss of phosphorus.
The alkalinity of cement is due to calcium oxide. In reported cases of cement burn,[1-3] most patients were unaware of the hazards of prolonged contact with cement.
He had invented a mixture containing naphtha, plus potassium nitrate and calcium oxide, perhaps (we don't know the exact recipe), which not only burned but would continue to burn on water even more fiercely.
The scientists achieved a 5-log reduction of bacteria at 25 C in 40 minutes using a concentration of 0.01% calcium oxide; in 30 minutes using 0.02% calcium oxide; in 20 minutes using 0.03% calcium oxide; and in 12 minutes using 0.04% calcium oxide.
Besides, thermodynamically speaking, it can be assumed that this type of oxide has been formed during the reaction between an acidic compound (manganese oxide) and an alkaline oxide (calcium oxide).
Then there is a completely different approach which, instead of employing solvents, uses calcium or carbonate looping technology--essentially taking limestone and reducing it to calcium oxide. For capture purposes, the C[O.sub.2] absorbs reactively on the calcium oxide, being converted to calcium carbonate.
The reactor concentrates solar energy using mirrors, in a chamber containing calcium oxide. At 400 degree Celsius, heat causes the calcium oxide to react with CO2 to form calcium carbonate.
There are other viable metal oxides for activating cure systems, for example, calcium oxide. While calcium oxide is a good choice (it does not form a prodegradant complex), it is not as active as zinc oxide.
The oil shale ash melting characteristics ([t.sub.A]--the initial deformation temperature; [t.sub.B]--the softening temperature and [t.sub.C]--the fluid temperature) depending on the calcium oxide content of ash have been investigated.