Calcium Oxide

Title: Calcium Oxide
CAS Registry Number: 1305-78-8
Additional Names: Lime; burnt lime; calx; quicklime
Molecular Formula: CaO
Molecular Weight: 56.08
Percent Composition: Ca 71.47%, O 28.53%
Literature References: Properly stored lime of commerce contains 90-95% free CaO. Commercial production from limestone: W. L. Faith et al., Industrial Chemicals (John Wiley, New York, 3rd ed., 1965) pp 482-487. Lab prepn by ignition of CaCO3: Ehrlich in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) p 931. Review: R. S. Boynton in Kirk-Othmer Encyclopedia of Chemical Technology vol. 14 (Wiley-Interscience, New York, 3rd ed., 1981) pp 343-382.
Properties: Crystals, white or grayish-white lumps, or granular powder; commercial material sometimes has a yellowish or brownish tint, due to iron. mp 2572°; bp 2850°; d 3.32-3.35. Readily absorbs CO2 and H2O from air, becoming air-slaked. Sol in water forming Ca(OH)2 and generating a large quantity of heat; sol in acids, glycerol, sugar soln; practically insol in alc. Keep tightly closed and dry.
Melting point: mp 2572°
Boiling point: bp 2850°
Density: d 3.32-3.35
CAUTION: Potential symptoms of overexposure are irritation of eyes, skin, upper respiratory tract; ulceration or perforation of nasal septum; pneumonia; dermatitis. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 48.
Use: In bricks, plaster, mortar, stucco and other building and construction materials; manuf of steel, aluminum, magnesium, and flotation of non-ferrous ores; manuf of glass, paper, Na2CO3 (Solvay process), Ca salts and many other industrial chemicals; dehairing hides; clarification of cane and beet sugar juices; in fungicides, insecticides, drilling fluids, lubricants; water and sewage treatment; in laboratory to absorb CO2 (the combination with NaOH is known as soda-lime, q.v.).
Calcium Palmitate Calcium Permanganate Calcium Peroxide Calcium Phenolsulfonate Calcium Phenoxide

Calcium oxide
Calcium oxide
Identifiers
CAS number 1305-78-8 YesY
PubChem 14778
ChemSpider 14095
UNII C7X2M0VVNH
UN number 1910
RTECS number EW3100000
ATCvet code QP53AX18
Jmol-3D images Image 1
Properties
Molecular formula CaO
Molar mass 56.0774 g/mol
Appearance White to pale yellow/brown powder
Odor odorless
Density 3.34 g/cm3[1]
Melting point 2613 °C, 2886 K, 4735 °F[1]
Boiling point 2850 °C, 3123 K (100 hPa)[2]
Solubility in water 1.19 g/L (25 °C), 0.57 g/L (100 °C), exothermic reaction[3]
Solubility in acids soluble (also in glycerol, sugar solution)
Solubility in methanol insoluble (also in diethyl ether, n-octanol)
Acidity (pKa) 12.8
Thermochemistry
Std molar
entropy So298
40 J·mol−1·K−1[4]
Std enthalpy of
formation ΔfHo298
−635 kJ·mol−1[4]
Hazards
MSDS [1]
EU Index Not listed
NFPA 704
NFPA 704.svg
0
3
2
Flash point Non-flammable
Related compounds
Other anions Calcium sulfide
Calcium hydroxide
Other cations Beryllium oxide
Magnesium oxide
Strontium oxide
Barium oxide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature. The broadly used term "lime" connotes calcium-containing inorganic materials, which include carbonates, oxides and hydroxides of calcium, silicon, magnesium, aluminium, and iron predominate, such as limestone. By contrast, "quicklime" specifically applies to a single chemical compound.

Quicklime is relatively inexpensive. Both it and a chemical derivative (calcium hydroxide, of which quicklime is the base anhydride) are important commodity chemicals.