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|Section2= |Section3= |Section5= |Section6= |Section7= |Section8= }} 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, in which carbonates, oxides and hydroxides of calcium, silicon, magnesium, aluminium, and iron predominate. By contrast, "quicklime" specifically applies to the single chemical compound calcium oxide. Calcium oxide which survives processing without reacting in building products such as cement is called free lime.〔("free lime" ). DictionaryOfConstruction.com.〕 Quicklime is relatively inexpensive. Both it and a chemical derivative (calcium hydroxide, of which quicklime is the base anhydride) are important commodity chemicals. ==Preparation== Calcium oxide is usually made by the thermal decomposition of materials such as limestone, or seashells, that contain calcium carbonate (CaCO3; mineral calcite) in a lime kiln. This is accomplished by heating the material to above ,〔Merck Index of chemicals and Drugs , 9th edition monograph 1650〕 a process called calcination or ''lime-burning'', to liberate a molecule of carbon dioxide (CO2); leaving quicklime. : CaCO3(s) → CaO(s) + CO2(g) The quicklime is not stable and, when cooled, will spontaneously react with CO2 from the air until, after enough time, it will be completely converted back to calcium carbonate unless slaked with water to set as lime plaster or lime mortar. Annual worldwide production of quicklime is around 283 million metric tons. China is by far the world's largest producer, with a total of around 170 million tonnes per year. The United States is the next largest, with around 20 million tonnes per year. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Calcium oxide」の詳細全文を読む スポンサード リンク
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