Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic and alkaline crystalline solid at room temperature.
The broadly used term lime connotes calcium-containing inorganic materials, in which carbonates, oxides and hydroxides of calcium, silicon, magnesium, aluminum, & iron predominate, such as limestone. By contrast, quicklime specifically applies to a single chemical compound.
Calcium oxide is usually made by the thermal decomposition of materials such as limestone, that contain calcium carbonate (CaCO3; mineral calcite) in a lime kiln. This is accomplished by heating the material to above 825 °C, a process called calcination or lime-burning, to liberate a molecule of carbon dioxide (CO2); leaving quicklime. The quicklime is not stable and, when cooled, will spontaneously react with CO2 from the air until, after enough time, it is completely converted back to calcium carbonate.
Inhalation of dust is highly irritating and possibly corrosive to the upper respiratory tract. May cause coughing, sneezing, labored breathing, and possibly burns with perforation of the nasal septum.
Corrosive. May attack the esophagus. Abdominal pain, nausea, vomiting may result. May cause serious alkali burns in mouth and throat.
Irritant; may cause severe corrosive damage.
Severe irritant, may damage eye tissues. Causes redness, tearing, blurred vision, pain.
Chronic inhalation of dust may cause inflammation of the respiratory passages, ulcers of the mucous membranes, and possible perforation of nasal septum.
Aggravation of Pre-existing Conditions:
Persons with pre-existing skin disorders or eye problems or impaired respiratory function may be more susceptible to the effects of the substance.
Use as a weapon
Historian and philosopher David Hume, in his history of England, recounts that early in the reign of Henry III, the English Navy destroyed an invading French fleet by blinding the enemy fleet with quicklime:
D’Albiney employed a stratagem against them, which is said to have contributed to the victory: Having gained the wind of the French, he came down upon them with violence; and throwing in their faces a great quantity of quicklime, which he purposely carried on board, he so blinded them, that they were disabled from defending themselves.
Quicklime is also thought to have been a component of Greek fire. Upon contact with water, quicklime would increase its temperature above 150 °C and ignite the fuel.
Because of vigorous reaction of quicklime with water, quicklime causes severe irritation when inhaled or placed in contact with moist skin or eyes. Inhalation may cause coughing, sneezing, labored breathing. It may then evolve into burns with perforation of the nasal septum, abdominal pain, nausea and vomiting. Although quicklime is not considered a fire hazard, its reaction with water can release enough heat to ignite combustible materials.
^ Merck Index of chemicals and Drugs , 9th edition monograph 1650
^ U.S. Patent 3,955,554, Solar heating system.
^ Gray, Theodore (September 2007). "Limelight in the Limelight". Popular Science: 84. http://www.popsci.com/node/9652.
^ Miller, M. Michael (2007). "Lime". Minerals Yearbook. U.S. Geological Survey. p. 43.13. http://minerals.usgs.gov/minerals/pubs/commodity/lime/myb1-2007-lime.pdf.
^ David Hume (1688). History of England. I. http://www.gutenberg.org/files/19212/19212-h/19212-h.htm#2H_4_0002.
^ Croddy, Eric (2002). Chemical and biological warfare: a comprehensive survey for the concerned citizen. Springer. p. 128. ISBN 0387950761. http://books.google.com/?id=MQMGhInCvlgC&pg=PA128.
^ CaO MSDS
A discussion of lime and its uses (US context) by the US Geological Survey
Factors Affecting the Quality of Quicklime
American Scientist (discussion of 14C dating of mortar)
Chemical of the Week - Lime
Lime production process presentation
Material Safety Data Sheet