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.

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.

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.

lime

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.

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
References in periodicals archive ?
4, hydration of calcium oxide CaO is going partially according to reaction CaO + [Ca.
Active phase of calcium oxide used as solid base catalyst for transesterification of soybean oil with refluxing methanol.
The contrasts represented by letters B and C allowed the evaluation of linear and quadratic order effects, respectively, as a function of the calcium oxide doses on the sugar cane.
Portland cement and MTA are rich in calcium oxide, which is converted to calcium hydroxide in aqueous solution.
Calcium aluminate of this structure is not very rich in calcium oxide and has a very high melting point of over 1600[degrees]C Kiessling, (1978).
The aim of the research was to use compost, bentonite and calcium oxide to neutralise potentially negative influence of soil contamination with petrol and diesel oil on the number of oligotrophic and copiotrophic bacteria.
So, for binding of silica, which is originally present in the NTMK slag and forms in the reduction reaction, significant additives of calcium oxide are necessary.
All catalysts showed a promoting effect to some extent, the best result was achieved on using zinc oxide at a concentration of 2% (based on dry Cotton stalls) followed by calcium oxide and titanium oxide at a concentration of I%.
Many reports have been focused on the sol gel derived hydroxyapatite and that showed the presence of secondary phase like calcium oxide and pyrophosphate.
The contents are heated (heat is produced by a natural reaction from mineral, calcium oxide and water) to 145 degrees F in six to eight minutes - a hot spot will turn from pink to white on the thermal ink label.
THE WATER REACTS WITH THE CALCIUM OXIDE IN THE INNER CONE, HEATING THE PRODUCT.
The sand cores were made predominately out of silica sand, which contained a significant amount of aluminum oxide as well as ferric oxide and calcium oxide.