Carbon dioxide (CO2) is a colourless gas with a sour taste and a mild harsh odour. It is one of the most important greenhouse gases linked to global warming, but it is a minor component of the Earth's atmosphere (about 3 volumes in 10,000), formed in the combustion of carbon-containing materials, fermentation, and animal respiration, and used by plants in carbohydrate photosynthesis.
Jan Baptista van Helmont, a Belgian scientist, identified carbon dioxide as a distinct gas early in the 17th century after observing it as a result of both fermentation and combustion. At 31 °C (87.4 °F), it liquefies to 75 kilogrammes per square centimetre (1,071 pounds per square inch), or 16–24 kg per sq cm (230–345 lb per sq in.) at 23–12 °C (10–10 °F). Carbon dioxide is used as a refrigerant, to inflate life rafts and life jackets, to blast coal, to foam rubber and plastics, to promote plant growth in greenhouses, to immobilise animals before slaughter, and to make carbonated beverages.
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