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 carbonate calcium 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.
..... Click the link for more information. (e.g., limestone limestone, 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.
..... Click the link for more information. ) 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 powder bleaching 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.
..... Click the link for more information. , calcium carbide, and calcium cyanamide; in water softeners; and in mortars and cements. In agriculture it is used for treating acidic soils (liming liming (līm`ĭng), application to the soil of calcium in various forms, generally as ground limestone, but also as marl, chalk,
..... Click the link for more information. ). 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 hydroxide calcium 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.
..... Click the link for more information. ; during the reaction (slaking) much heat is given off and the solid nearly doubles its volume.

lime

or quicklime or calcium oxide

Inorganic compound, white or grayish white solid, chemical formula CaO, made by roasting limestone (calcium carbonate, CaCO₃) until all the carbon dioxide (CO₂) is driven off. One of the four most important basic chemical commodities, it is used as a refractory, as a flux in steel manufacture, as a CO₂ absorbent, to remove contaminants from stack gases, to neutralize various acids, in pulp and paper, in insecticides and fungicides, in sewage treatment, and in the manufacture of glass, calcium carbide, and sodium carbonate. Adding water to lime yields calcium hydroxide (slaked lime, calcium hydrate, hydrated lime, or caustic lime), which is used in mortar, plasters, cements, whitewash, hide dehairing, and water softening and purification and as a source of other calcium salts.

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

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.