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|Section2= |Section3= |Section5= |Section6= |Section7= |Section8= }} Carbon dioxide (chemical formula CO2) is a colorless, odorless gas vital to life on Earth. This naturally occurring chemical compound is composed of a carbon atom covalently double bonded to two oxygen atoms. Carbon dioxide exists in the Earth's atmosphere as a trace gas at a concentration of about 0.04 percent (400 ppm) by volume.〔 Natural sources include volcanoes, hot springs and geysers and it is freed from carbonate rocks by dissolution in water and acids. Since carbon dioxide is soluble in water, it occurs naturally in groundwater, rivers and lakes, in ice caps and glaciers and in seawater. It is present in deposits of petroleum and natural gas.〔(【引用サイトリンク】title=General Properties and Uses of Carbon Dioxide, Good Plant Design and Operation for Onshore Carbon Capture Installations and Onshore Pipelines )〕 Atmospheric carbon dioxide is the primary source of carbon in life on Earth and its concentration in Earth's pre-industrial atmosphere since late in the Precambrian was regulated by photosynthetic organisms and geological phenomena. As part of the carbon cycle, plants, algae, and cyanobacteria use light energy to photosynthesize carbohydrate from carbon dioxide and water, with oxygen produced as a waste product. Carbon dioxide is produced by plants during respiration.〔(Food Factories ). www.legacyproject.org. Retrieved 2011-10-10.〕 Carbon dioxide () is a product of respiration of all aerobic organisms. It is returned to water via the gills of fish and to the air via the lungs of air-breathing land animals, including humans. Carbon dioxide is produced during the processes of decay of organic materials and the fermentation of sugars in bread, beer and winemaking. It is produced by combustion of wood, carbohydrates and fossil fuels such as coal, peat, petroleum and natural gas. It is a versatile industrial material, used, for example, as an inert gas in welding and fire extinguishers, as a pressurizing gas in air guns and oil recovery, as a chemical feedstock and in liquid form as a solvent in decaffeination of coffee and supercritical drying. It is added to drinking water and carbonated beverages including beer and champagne to add sparkle. The frozen solid form of CO2, known as "dry ice" is used as a refrigerant and as an abrasive in dry-ice blasting. Carbon dioxide is an important greenhouse gas. Burning of carbon-based fuels since the industrial revolution has rapidly increased its concentration in the atmosphere, leading to global warming. It is also a major cause of ocean acidification since it dissolves in water to form carbonic acid.〔National Research Council. "Summary." (Ocean Acidification: A National Strategy to Meet the Challenges of a Changing Ocean ). Washington, DC: The National Academies Press, 2010. 1. Also published in print by National Academic Press.〕 == Background == Carbon dioxide was the first gas to be described as a discrete substance. In about 1640, the Flemish chemist Jan Baptist van Helmont observed that when he burned charcoal in a closed vessel, the mass of the resulting ash was much less than that of the original charcoal. His interpretation was that the rest of the charcoal had been transmuted into an invisible substance he termed a "gas" or "wild spirit" (''spiritus sylvestre'').〔Ebbe Almqvist (2003): ''History of industrial gases'', Springer, 2003, ISBN 9780306472770, p. 93〕 The properties of carbon dioxide were studied more thoroughly in the 1750s by the Scottish physician Joseph Black. He found that limestone (calcium carbonate) could be heated or treated with acids to yield a gas he called "fixed air." He observed that the fixed air was denser than air and supported neither flame nor animal life. Black also found that when bubbled through limewater (a saturated aqueous solution of calcium hydroxide), it would precipitate calcium carbonate. He used this phenomenon to illustrate that carbon dioxide is produced by animal respiration and microbial fermentation. In 1772, English chemist Joseph Priestley published a paper entitled ''Impregnating Water with Fixed Air'' in which he described a process of dripping sulfuric acid (or ''oil of vitriol'' as Priestley knew it) on chalk in order to produce carbon dioxide, and forcing the gas to dissolve by agitating a bowl of water in contact with the gas. Carbon dioxide was first liquefied (at elevated pressures) in 1823 by Humphry Davy and Michael Faraday. The earliest description of solid carbon dioxide was given by Adrien-Jean-Pierre Thilorier, who in 1835 opened a pressurized container of liquid carbon dioxide, only to find that the cooling produced by the rapid evaporation of the liquid yielded a "snow" of solid CO2.〔Thilorier, Adrien-Jean-Pierre (1835) ("Solidification de l’acide carbonique" ) (Solidification of carbonic acid), ''Comptes rendus'' ..., 1 : 194–196〕〔("Solidification of carbonic acid" ), ''The London and Edinburgh Philosophical Magazine'', 8 : 446–447 (1836).〕 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「Carbon dioxide」の詳細全文を読む スポンサード リンク
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