![]() 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). In the seventeenth century, 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. See also: Supercritical carbon dioxide and dry iceĬarbon dioxide was one of the first gases to be described as a substance distinct from air. Unlike silica and germania glasses, however, carbonia glass is not stable at normal pressures and reverts back to gas when pressure is released. This discovery confirmed the theory that carbon dioxide could exist in a glass state similar to other members of its elemental family, like silicon ( silica glass) and germanium. This form of glass, called carbonia, was produced by supercooling heated CO 2 at extreme pressure (40–48 GPa or about 400,000 atmospheres) in a diamond anvil. Īn alternative form of solid carbon dioxide, an amorphous glass-like form, is possible, although not at atmospheric pressure. The critical point is 7.38 MPa at 31.1 ☌. ![]() Liquid carbon dioxide forms only at pressures above 5.1 atm the triple point of carbon dioxide is about 518 kPa at −56.6 ☌ (See phase diagram, above). The largest non-cooling use for dry ice is blast cleaning. It can often be found in grocery stores and laboratories, and it is also used in the shipping industry. A convenient property for this purpose is that solid carbon dioxide sublimes directly into the gas phase leaving no liquid. Dry ice is commonly used as a cooling agent, and it is relatively inexpensive. ![]() It was first observed in 1825 by the French chemist Charles Thilorier. Solid carbon dioxide is normally called " dry ice", a generic trademark. It has no electrical dipole, and as it is fully oxidized, it is moderately reactive and is non-flammable, but will support the combustion of metals such as magnesium.Īt −78.51 ° C or −109.3 ° F, carbon dioxide changes directly from a solid phase to a gaseous phase through sublimation, or from gaseous to solid through deposition. The carbon dioxide molecule (O=C=O) contains two double bonds and has a linear shape. Īt standard temperature and pressure, the density of carbon dioxide is around 1.98 kg/m 3, about 1.5 times that of air. Amounts above 5,000 ppm are considered very unhealthy, and those above about 50,000 ppm (equal to 5% by volume) are considered dangerous to animal life. This sensation can also occur during an attempt to stifle a burp after drinking a carbonated beverage. These effects result from the gas dissolving in the mucous membranes and saliva, forming a weak solution of carbonic acid. When inhaled at concentrations much higher than usual atmospheric levels, it can produce a sour taste in the mouth and a stinging sensation in the nose and throat. Carbon dioxideįor more details on this topic, see Carbon dioxide (data page).Carbon dioxide is a colourless, odorless gas. Carbon dioxide is a greenhouse gas as it transmits visible light but absorbs strongly in the infrared and near-infrared. Carbon dioxide exists in Earth's atmosphere currently at a globally averaged concentration of approximately 385 parts per million by volume. It is a gas at standard temperature and pressure. 4.7 Pharmaceutical and other chemical processingĬarbon dioxide ( chemical formula: CO 2) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom.In its solid state, carbon dioxide is commonly called dry ice.ĬO 2 is an acidic oxide: an aqueous solution turns litmus from blue to pink.ĬO 2 in concentrations of 7% to 10% cause dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour. At 1 atm it is a solid at temperatures below −78 ☌. Over very long time scales (thousands to millions of years), concentrations are influenced by emissions from volcanoes and other geothermal processes such as hot springs and geysers and by the dissolution of carbonates in crustal rocks.Ĭarbon dioxide has no liquid state at pressures below 5.1 atm. Carbon dioxide is generated as a by-product of the combustion of fossil fuels or the burning of vegetable matter, among other chemical processes. It is, therefore, a major component of the carbon cycle. It is produced during respiration by plants, and by all animals, fungi and microorganisms that depend on living and decaying plants for food, either directly or indirectly. Carbon dioxide is used by plants during photosynthesis to make sugars which may either be consumed again in respiration or used as the raw material to produce polysaccharides such as starch and cellulose, proteins and the wide variety of other organic compounds required for plant growth and development.
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