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Carbon dioxide

Names
Other names Carbonic acid gas Carbonic anhydride Carbonic dioxide Carbon(IV) oxide R-744 (refrigerant) R744 (refrigerant alternative spelling) Dry ice (solid phase)
Identifiers
CAS Number	124-38-9
3D model (JSmol)	Interactive image Interactive image
3DMet	B01131
Beilstein Reference	1900390
ChEBI	CHEBI:16526
ChEMBL	ChEMBL1231871
ChemSpider	274
ECHA InfoCard	100.004.271
EC Number	204-696-9
E number	E290 (preservatives)
Gmelin Reference	989
KEGG	D00004
MeSH	Carbon+dioxide
PubChem CID	280
RTECS number	FF6400000
UNII	142M471B3J
UN number	1013 (gas), 1845 (solid)
CompTox Dashboard (EPA)	DTXSID4027028
InChI InChI=1S/CO2/c2-1-3  Key: CURLTUGMZLYLDI-UHFFFAOYSA-N  InChI=1/CO2/c2-1-3 Key: CURLTUGMZLYLDI-UHFFFAOYAO
SMILES O=C=O C(=O)=O
Properties
Chemical formula	CO2
Molar mass	44.009 g·mol−1
Appearance	Colorless gas
Odor	Low concentrations: none High concentrations: sharp; acidic[1]
Density	1562 kg/m3 (solid at 1 atm (100 kPa) and −78.5 °C (−109.3 °F)) 1101 kg/m3 (liquid at saturation −37 °C (−35 °F)) 1.977 kg/m3 (gas at 1 atm (100 kPa) and 0 °C (32 °F))
Critical point (T, P)	304.128(15) K[2] (30.978(15) °C), 7.3773(30) MPa[2] (72.808(30) atm)
Sublimation conditions	194.6855(30) K (−78.4645(30) °C) at 1 atm (0.101325 MPa)
Solubility in water	1.45 g/L at 25 °C (77 °F), 100 kPa (0.99 atm)
Vapor pressure	5.7292(30) MPa, 56.54(30) atm (20 °C (293.15 K))
Acidity (pKa)	6.35, 10.33
Magnetic susceptibility (χ)	−20.5·10−6 cm3/mol
Thermal conductivity	0.01662 W·m−1·K−1 (300 K (27 °C; 80 °F))[3]
Refractive index (nD)	1.00045
Viscosity	14.90 μPa·s at 25 °C (298 K)[4] 70 μPa·s at −78.5 °C (194.7 K)
Dipole moment	0 D
Structure
Crystal structure	Trigonal
Molecular shape	Linear
Thermochemistry
Heat capacity (C)	37.135 J/K·mol
Std molar entropy (S⦵298)	214 J·mol−1·K−1
Std enthalpy of formation (ΔfH⦵298)	−393.5 kJ·mol−1
Pharmacology
ATC code	V03AN02 (WHO)
Hazards
NFPA 704 (fire diamond)	[7][8] 2 0 0 SA
Lethal dose or concentration (LD, LC):
LCLo (lowest published)	90,000 ppm (human, 5 min)[6]
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 5000 ppm (9000 mg/m3)[5]
REL (Recommended)	TWA 5000 ppm (9000 mg/m3), ST 30,000 ppm (54,000 mg/m3)[5]
IDLH (Immediate danger)	40,000 ppm[5]
Safety data sheet (SDS)	Sigma-Aldrich
Related compounds
Other anions	Carbon disulfide Carbon diselenide Carbon ditelluride
Other cations	Silicon dioxide Germanium dioxide Tin dioxide Lead dioxide
Related carbon oxides	Carbon monoxide Carbon suboxide Dicarbon monoxide Carbon trioxide
Related compounds	Carbonic acid Carbonyl sulfide
Supplementary data page
Carbon dioxide (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).  verify (what is  ?) Infobox references

Carbon dioxide (chemical formula CO₂) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas. It is a trace gas in Earth’s atmosphere at 421 parts per million (ppm), or about 0.04% by volume (as of May 2022), having risen from pre-industrial levels of 280 ppm.^[9][10] Burning fossil fuels is the primary cause of these increased CO₂ concentrations and also the primary cause of climate change.^[11] Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, and seawater. When carbon dioxide dissolves in water, it forms carbonate and mainly bicarbonate (HCO⁻
₃), which causes ocean acidification as atmospheric CO₂ levels increase.^[12]

As the source of available carbon in the carbon cycle, atmospheric CO₂ is the primary carbon source for life on Earth. Its concentration in Earth’s pre-industrial atmosphere since late in the Precambrian has been regulated by organisms and geological phenomena. Plants, algae and cyanobacteria use energy from sunlight to synthesize carbohydrates from carbon dioxide and water in a process called photosynthesis, which produces oxygen as a waste product.^[13] In turn, oxygen is consumed and CO₂ is released as waste by all aerobic organisms when they metabolize organic compounds to produce energy by respiration.^[14] CO₂ is released from organic materials when they decay or combust, such as in forest fires. Since plants require CO₂ for photosynthesis, and humans and animals depend on plants for food, CO₂ is necessary for the survival of life on earth.

Carbon dioxide is 53% more dense than dry air, but is long lived and thoroughly mixes in the atmosphere. About half of excess CO₂ emissions to the atmosphere are absorbed by land and ocean carbon sinks.^[15] These sinks can become saturated and are volatile, as decay and wildfires result in the CO₂ being released back into the atmosphere.^[16] CO₂ is eventually sequestered (stored for the long term) in rocks and organic deposits like coal, petroleum and natural gas. Sequestered CO₂ is released into the atmosphere through burning fossil fuels or naturally by volcanoes, hot springs, geysers, and when carbonate rocks dissolve in water or react with acids.

CO₂ 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, and as a supercritical fluid solvent in decaffeination of coffee and supercritical drying.^[17] It is a byproduct of fermentation of sugars in bread, beer and wine making, and is added to carbonated beverages like seltzer and beer for effervescence. It has a sharp and acidic odor and generates the taste of soda water in the mouth,^[18] but at normally encountered concentrations it is odorless.^[1]

Chemical and physical properties

Structure, bonding and molecular vibrations

The symmetry of a carbon dioxide molecule is linear and centrosymmetric at its equilibrium geometry. The length of the carbon-oxygen bond in carbon dioxide is 116.3 pm, noticeably shorter than the roughly 140-pm length of a typical single C–O bond, and shorter than most other C–O multiply-bonded functional groups such as carbonyls.^[19] Since it is centrosymmetric, the molecule has no electric dipole moment.

As a linear triatomic molecule, CO₂ has four vibrational modes as shown in the diagram. In the symmetric and the antisymmetric stretching modes, the atoms move along the axis of the molecule. There are two bending modes, which are degenerate, meaning that they have the same frequency and same energy, because of the symmetry of the molecule. When a molecule touches a surface or touches another molecule, the two bending modes can differ in frequency because the interaction is different for the two modes. Some of the vibrational modes are observed in the infrared (IR) spectrum: the antisymmetric stretching mode at wavenumber 2349 cm⁻¹ (wavelength 4.25 μm) and the degenerate pair of bending modes at 667 cm⁻¹ (wavelength 15 μm). The symmetric stretching mode does not create an electric dipole so is not observed in IR spectroscopy, but it is detected in by Raman spectroscopy at 1388 cm⁻¹ (wavelength 7.2 μm).^[20]

In the gas phase, carbon dioxide molecules undergo significant vibrational motions and do not keep a fixed structure. However, in a Coulomb explosion imaging experiment, an instantaneous image of the molecular structure can be deduced. Such an experiment^[21] has been performed for carbon dioxide.
The result of this experiment, and the conclusion of theoretical calculations^[22] based on an ab initio potential energy surface of the molecule, is that none of the
molecules in the gas phase are ever exactly linear. This counter-intuitive result is trivially due to
the fact that the nuclear motion volume element vanishes for linear geometries.^[22]
This is so for all molecules (except diatomics!).

In aqueous solution

Carbon dioxide is soluble in water, in which it reversibly forms H₂CO₃ (carbonic acid), which is a weak acid since its ionization in water is incomplete.

The hydration equilibrium constant of carbonic acid is, at 25 °C:

Hence, the majority of the carbon dioxide is not converted into carbonic acid, but remains as CO₂ molecules, not affecting the pH.

The relative concentrations of CO₂, H₂CO₃, and the deprotonated forms HCO−3 (bicarbonate) and CO2−3(carbonate) depend on the pH. As shown in a Bjerrum plot, in neutral or slightly alkaline water (pH > 6.5), the bicarbonate form predominates (>50%) becoming the most prevalent (>95%) at the pH of seawater. In very alkaline water (pH > 10.4), the predominant (>50%) form is carbonate. The oceans, being mildly alkaline with typical pH = 8.2–8.5, contain about 120 mg of bicarbonate per liter.

Being diprotic, carbonic acid has two acid dissociation constants, the first one for the dissociation into the bicarbonate (also called hydrogen carbonate) ion (HCO−3):

K_a1 = 2.5×10⁻⁴ mol/L; pK_a1 = 3.6 at 25 °C.^[19]

This is the true first acid dissociation constant, defined as

where the denominator includes only covalently bound H₂CO₃ and does not include hydrated CO_2(aq). The much smaller and often-quoted value near 4.16×10⁻⁷ is an apparent value calculated on the (incorrect) assumption that all dissolved CO₂ is present as carbonic acid, so that

Since most of the dissolved CO₂remains as CO₂ molecules, K_a1(apparent) has a much larger denominator and a much smaller value than the true K_a1.^[23]

The bicarbonate ion is an amphoteric species that can act as an acid or as a base, depending on pH of the solution. At high pH, it dissociates significantly into the carbonate ion (CO2−3):

K_a2 = 4.69×10⁻¹¹ mol/L; pK_a2 = 10.329

In organisms carbonic acid production is catalysed by the enzyme, carbonic anhydrase.

Chemical reactions of CO₂

CO₂ is a potent electrophile having an electrophilic reactivity that is comparable to benzaldehyde or strong α,β-unsaturated carbonyl compounds. However, unlike electrophiles of similar reactivity, the reactions of nucleophiles with CO₂ are thermodynamically less favored and are often found to be highly reversible.^[24] Only very strong nucleophiles, like the carbanions provided by Grignard reagents and organolithium compounds react with CO₂ to give carboxylates:

where M = Li or Mg Br and R = alkyl or aryl.

In metal carbon dioxide complexes, CO₂ serves as a ligand, which can facilitate the conversion of CO₂ to other chemicals.^[25]

The reduction of CO₂ to CO is ordinarily a difficult and slow reaction:

Photoautotrophs (i.e. plants and cyanobacteria) use the energy contained in sunlight to photosynthesize simple sugars from CO₂ absorbed from the air and water:

The redox potential for this reaction near pH 7 is about −0.53 V versus the standard hydrogen electrode. The nickel-containing enzyme carbon monoxide dehydrogenase catalyses this process.^[26]

Physical properties

Carbon dioxide is colorless. At low concentrations the gas is odorless; however, at sufficiently high concentrations, it has a sharp, acidic odor.^[1] At standard temperature and pressure, the density of carbon dioxide is around 1.98 kg/m³, about 1.53 times that of air.^[27]

Carbon dioxide has no liquid state at pressures below 0.51795(10) MPa^[2] (5.11177(99) atm). At a pressure of 1 atm (0.101325 MPa), the gas deposits directly to a solid at temperatures below 194.6855(30) K^[2] (−78.4645(30) °C) and the solid sublimes directly to a gas above this temperature. In its solid state, carbon dioxide is commonly called dry ice.

Liquid carbon dioxide forms only at pressures above 0.51795(10) MPa^[2] (5.11177(99) atm); the triple point of carbon dioxide is 216.592(3) K^[2] (−56.558(3) °C) at 0.51795(10) MPa^[2] (5.11177(99) atm) (see phase diagram). The critical point is 304.128(15) K^[2] (30.978(15) °C) at 7.3773(30) MPa^[2] (72.808(30) atm). Another form of solid carbon dioxide observed at high pressure is an amorphous glass-like solid.^[28] This form of glass, called carbonia, is produced by supercooling heated CO₂ at extreme pressures (40–48 GPa, or about 400,000 atmospheres) in a diamond anvil. This discovery confirmed the theory that carbon dioxide could exist in a glass state similar to other members of its elemental family, like silicon dioxide (silica glass) and germanium dioxide. Unlike silica and germania glasses, however, carbonia glass is not stable at normal pressures and reverts to gas when pressure is released.

At temperatures and pressures above the critical point, carbon dioxide behaves as a supercritical fluid known as supercritical carbon dioxide.

Table of thermal and physical properties of saturated liquid carbon dioxide:^[29][30]

Temperature (°C)	Density (kg/m^3)	Specific heat (kJ/kg K)	Kinematic viscosity (m^2/s)	Conductivity (W/m K)	Thermal diffusivity (m^2/s)	Prandtl Number	Bulk modulus (K^-1)
-50	1156.34	1.84	1.19E-07	0.0855	4.02E-08	2.96	—
-40	1117.77	1.88	1.18E-07	0.1011	4.81E-08	2.46	—
-30	1076.76	1.97	1.17E-07	0.1116	5.27E-08	2.22	—
-20	1032.39	2.05	1.15E-07	0.1151	5.45E-08	2.12	—
-10	983.38	2.18	1.13E-07	0.1099	5.13E-08	2.2	—
0	926.99	2.47	1.08E-07	0.1045	4.58E-08	2.38	—
10	860.03	3.14	1.01E-07	0.0971	3.61E-08	2.8	—
20	772.57	5	9.10E-08	0.0872	2.22E-08	4.1	1.40E-02
30	597.81	36.4	8.00E-08	0.0703	0.279E-08	28.7	—

Table of thermal and physical properties of carbon dioxide (CO2) at atmospheric pressure:^[29][30]

Temperature (K)	Density (kg/m^3)	Specific heat (kJ/kg °C)	Dynamic viscosity (kg/m s)	Kinematic viscosity (m^2/s)	Thermal conductivity (W/m °C)	Thermal diffusivity (m^2/s)	Prandtl Number
220	2.4733	0.783	1.11E-05	4.49E-06	0.010805	5.92E-06	0.818
250	2.1657	0.804	1.26E-05	5.81E-06	0.012884	7.40E-06	0.793
300	1.7973	0.871	1.50E-05	8.32E-06	0.016572	1.06E-05	0.77
350	1.5362	0.9	1.72E-05	1.12E-05	0.02047	1.48E-05	0.755
400	1.3424	0.942	1.93E-05	1.44E-05	0.02461	1.95E-05	0.738
450	1.1918	0.98	2.13E-05	1.79E-05	0.02897	2.48E-05	0.721
500	1.0732	1.013	2.33E-05	2.17E-05	0.03352	3.08E-05	0.702
550	0.9739	1.047	2.51E-05	2.57E-05	0.03821	3.75E-05	0.685
600	0.8938	1.076	2.68E-05	3.00E-05	0.04311	4.48E-05	0.668
650	0.8143	1.1	2.88E-05	3.54E-05	0.0445	4.97E-05	0.712
700	0.7564	1.13E+00	3.05E-05	4.03E-05	0.0481	5.63E-05	0.717
750	0.7057	1.15	3.21E-05	4.55E-05	0.0517	6.37E-05	0.714
800	0.6614	1.17E+00	3.37E-05	5.10E-05	0.0551	7.12E-05	0.716

Biological role

Carbon dioxide is an end product of cellular respiration in organisms that obtain energy by breaking down sugars, fats and amino acids with oxygen as part of their metabolism. This includes all plants, algae and animals and aerobic fungi and bacteria. In vertebrates, the carbon dioxide travels in the blood from the body’s tissues to the skin (e.g., amphibians) or the gills (e.g., fish), from where it dissolves in the water, or to the lungs from where it is exhaled. During active photosynthesis, plants can absorb more carbon dioxide from the atmosphere than they release in respiration.

Photosynthesis and carbon fixation

Carbon fixation is a biochemical process by which atmospheric carbon dioxide is incorporated by plants, algae and (cyanobacteria) into energy-rich organic molecules such as glucose, thus creating their own food by photosynthesis. Photosynthesis uses carbon dioxide and water to produce sugars from which other organic compounds can be constructed, and oxygen is produced as a by-product.

Ribulose-1,5-bisphosphate carboxylase oxygenase, commonly abbreviated to RuBisCO, is the enzyme involved in the first major step of carbon fixation, the production of two molecules of 3-phosphoglycerate from CO₂ and ribulose bisphosphate, as shown in the diagram at left.

RuBisCO is thought to be the single most abundant protein on Earth.^[31]

Phototrophs use the products of their photosynthesis as internal food sources and as raw material for the biosynthesis of more complex organic molecules, such as polysaccharides, nucleic acids and proteins. These are used for their own growth, and also as the basis of the food chains and webs that feed other organisms, including animals such as ourselves. Some important phototrophs, the coccolithophores synthesise hard calcium carbonate scales.^[32] A globally significant species of coccolithophore is Emiliania huxleyi whose calcite scales have formed the basis of many sedimentary rocks such as limestone, where what was previously atmospheric carbon can remain fixed for geological timescales.

Plants can grow as much as 50 percent faster in concentrations of 1,000 ppm CO₂ when compared with ambient conditions, though this assumes no change in climate and no limitation on other nutrients.^[33] Elevated CO₂ levels cause increased growth reflected in the harvestable yield of crops, with wheat, rice and soybean all showing increases in yield of 12–14% under elevated CO₂ in FACE experiments.^[34][35]

Increased atmospheric CO₂ concentrations result in fewer stomata developing on plants^[36] which leads to reduced water usage and increased water-use efficiency.^[37] Studies using FACE have shown that CO₂ enrichment leads to decreased concentrations of micronutrients in crop plants.^[38] This may have knock-on effects on other parts of ecosystems as herbivores will need to eat more food to gain the same amount of protein.^[39]

The concentration of secondary metabolites such as phenylpropanoids and flavonoids can also be altered in plants exposed to high concentrations of CO₂.^[40][41]

Plants also emit CO₂ during respiration, and so the majority of plants and algae, which use C3 photosynthesis, are only net absorbers during the day. Though a growing forest will absorb many tons of CO₂ each year, a mature forest will produce as much CO₂ from respiration and decomposition of dead specimens (e.g., fallen branches) as is used in photosynthesis in growing plants.^[42] Contrary to the long-standing view that they are carbon neutral, mature forests can continue to accumulate carbon^[43] and remain valuable carbon sinks, helping to maintain the carbon balance of Earth’s atmosphere. Additionally, and crucially to life on earth, photosynthesis by phytoplankton consumes dissolved CO₂ in the upper ocean and thereby promotes the absorption of CO₂ from the atmosphere.^[44]

Toxicity

Carbon dioxide content in fresh air (averaged between sea-level and 10 kPa level, i.e., about 30 km (19 mi) altitude) varies between 0.036% (360 ppm) and 0.041% (412 ppm), depending on the location.^{[46][clarification needed]}

CO₂ is an asphyxiant gas and not classified as toxic or harmful in accordance with Globally Harmonized System of Classification and Labelling of Chemicals standards of United Nations Economic Commission for Europe by using the OECD Guidelines for the Testing of Chemicals. In concentrations up to 1% (10,000 ppm), it will make some people feel drowsy and give the lungs a stuffy feeling.^[45] Concentrations of 7% to 10% (70,000 to 100,000 ppm) may cause suffocation, even in the presence of sufficient oxygen, manifesting as dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour.^[47] The physiological effects of acute carbon dioxide exposure are grouped together under the term hypercapnia, a subset of asphyxiation.

Because it is heavier than air, in locations where the gas seeps from the ground (due to sub-surface volcanic or geothermal activity) in relatively high concentrations, without the dispersing effects of wind, it can collect in sheltered/pocketed locations below average ground level, causing animals located therein to be suffocated. Carrion feeders attracted to the carcasses are then also killed. Children have been killed in the same way near the city of Goma by CO₂ emissions from the nearby volcano Mount Nyiragongo.^[48] The Swahili term for this phenomenon is mazuku.

Adaptation to increased concentrations of CO₂ occurs in humans, including modified breathing and kidney bicarbonate production, in order to balance the effects of blood acidification (acidosis). Several studies suggested that 2.0 percent inspired concentrations could be used for closed air spaces (e.g. a submarine) since the adaptation is physiological and reversible, as deterioration in performance or in normal physical activity does not happen at this level of exposure for five days.^[49][50] Yet, other studies show a decrease in cognitive function even at much lower levels.^[51][52] Also, with ongoing respiratory acidosis, adaptation or compensatory mechanisms will be unable to reverse such condition.

Below 1%

There are few studies of the health effects of long-term continuous CO₂ exposure on humans and animals at levels below 1%. Occupational CO₂ exposure limits have been set in the United States at 0.5% (5000 ppm) for an eight-hour period.^[53] At this CO₂ concentration, International Space Station crew experienced headaches, lethargy, mental slowness, emotional irritation, and sleep disruption.^[54] Studies in animals at 0.5% CO₂ have demonstrated kidney calcification and bone loss after eight weeks of exposure.^[55] A study of humans exposed in 2.5 hour sessions demonstrated significant negative effects on cognitive abilities at concentrations as low as 0.1% (1000 ppm) CO₂ likely due to CO₂ induced increases in cerebral blood flow.^[51] Another study observed a decline in basic activity level and information usage at 1000 ppm, when compared to 500 ppm.^[52] However a review of the literature found that most studies on the phenomenon of carbon dioxide induced cognitive impairment to have a small effect on high-level decision making and most of the studies were confounded by inadequate study designs, environmental comfort, uncertainties in exposure doses and differing cognitive assessments used.^[56] Similarly a study on the effects of the concentration of CO₂ in motorcycle helmets has been criticized for having dubious methodology in not noting the self-reports of motorcycle riders and taking measurements using mannequins. Further when normal motorcycle conditions were achieved (such as highway or city speeds) or the visor was raised the concentration of CO₂ declined to safe levels (0.2%).^[57][58]

Ventilation

Poor ventilation is one of the main causes of excessive CO₂ concentrations in closed spaces, leading to poor indoor air quality. Carbon dioxide differential above outdoor concentrations at steady state conditions (when the occupancy and ventilation system operation are sufficiently long that CO₂ concentration has stabilized) are sometimes used to estimate ventilation rates per person.^{[citation needed]} Higher CO₂ concentrations are associated with occupant health, comfort and performance degradation.^[59][60] ASHRAE Standard 62.1–2007 ventilation rates may result in indoor concentrations up to 2,100 ppm above ambient outdoor conditions. Thus if the outdoor concentration is 400 ppm, indoor concentrations may reach 2,500 ppm with ventilation rates that meet this industry consensus standard. Concentrations in poorly ventilated spaces can be found even higher than this (range of 3,000 or 4,000 ppm).

Miners, who are particularly vulnerable to gas exposure due to insufficient ventilation, referred to mixtures of carbon dioxide and nitrogen as «blackdamp», «choke damp» or «stythe». Before more effective technologies were developed, miners would frequently monitor for dangerous levels of blackdamp and other gases in mine shafts by bringing a caged canary with them as they worked. The canary is more sensitive to asphyxiant gases than humans, and as it became unconscious would stop singing and fall off its perch. The Davy lamp could also detect high levels of blackdamp (which sinks, and collects near the floor) by burning less brightly, while methane, another suffocating gas and explosion risk, would make the lamp burn more brightly.

In February 2020, three people died from suffocation at a party in Moscow when dry ice (frozen CO₂) was added to a swimming pool to cool it down.^[61] A similar accident occurred in 2018 when a woman died from CO₂ fumes emanating from the large amount of dry ice she was transporting in her car.^[62]

Outdoor areas with elevated concentrations

Local concentrations of carbon dioxide can reach high values near strong sources, especially those that are isolated by surrounding terrain. At the Bossoleto hot spring near Rapolano Terme in Tuscany, Italy, situated in a bowl-shaped depression about 100 m (330 ft) in diameter, concentrations of CO₂ rise to above 75% overnight, sufficient to kill insects and small animals. After sunrise the gas is dispersed by convection.^[63] High concentrations of CO₂ produced by disturbance of deep lake water saturated with CO₂ are thought to have caused 37 fatalities at Lake Monoun, Cameroon in 1984 and 1700 casualties at Lake Nyos, Cameroon in 1986.^[64]

Human physiology

Content

Reference ranges or averages for partial pressures of carbon dioxide (abbreviated pCO₂)

Blood compartment	(kPa)	(mm Hg)
Venous blood carbon dioxide	5.5–6.8	41–51[65]	41–51[65]
Alveolar pulmonary gas pressures	4.8	36	36
Arterial blood carbon dioxide	4.7–6.0	35–45[65]	35–45[65]

The body produces approximately 2.3 pounds (1.0 kg) of carbon dioxide per day per person,^[66] containing 0.63 pounds (290 g) of carbon. In humans, this carbon dioxide is carried through the venous system and is breathed out through the lungs, resulting in lower concentrations in the arteries. The carbon dioxide content of the blood is often given as the partial pressure, which is the pressure which carbon dioxide would have had if it alone occupied the volume.^[67] In humans, the blood carbon dioxide contents is shown in the adjacent table.

Transport in the blood

CO₂ is carried in blood in three different ways. (Exact percentages vary between arterial and venous blood).

• Majority (about 70% to 80%) is converted to bicarbonate ions HCO−3 by the enzyme carbonic anhydrase in the red blood cells,^[68] by the reaction CO₂ + H₂O → H₂CO₃ → H⁺ + HCO−3.
• 5–10% is dissolved in blood plasma^[68]
• 5–10% is bound to hemoglobin as carbamino compounds^[68]

Hemoglobin, the main oxygen-carrying molecule in red blood cells, carries both oxygen and carbon dioxide. However, the CO₂ bound to hemoglobin does not bind to the same site as oxygen. Instead, it combines with the N-terminal groups on the four globin chains. However, because of allosteric effects on the hemoglobin molecule, the binding of CO₂ decreases the amount of oxygen that is bound for a given partial pressure of oxygen. This is known as the Haldane Effect, and is important in the transport of carbon dioxide from the tissues to the lungs. Conversely, a rise in the partial pressure of CO₂ or a lower pH will cause offloading of oxygen from hemoglobin, which is known as the Bohr effect.

Regulation of respiration

Carbon dioxide is one of the mediators of local autoregulation of blood supply. If its concentration is high, the capillaries expand to allow a greater blood flow to that tissue.^[69]

Bicarbonate ions are crucial for regulating blood pH. A person’s breathing rate influences the level of CO₂ in their blood. Breathing that is too slow or shallow causes respiratory acidosis, while breathing that is too rapid leads to hyperventilation, which can cause respiratory alkalosis.^[70]

Although the body requires oxygen for metabolism, low oxygen levels normally do not stimulate breathing. Rather, breathing is stimulated by higher carbon dioxide levels. As a result, breathing low-pressure air or a gas mixture with no oxygen at all (such as pure nitrogen) can lead to loss of consciousness without ever experiencing air hunger. This is especially perilous for high-altitude fighter pilots. It is also why flight attendants instruct passengers, in case of loss of cabin pressure, to apply the oxygen mask to themselves first before helping others; otherwise, one risks losing consciousness.^[68]

The respiratory centers try to maintain an arterial CO₂ pressure of 40 mm Hg. With intentional hyperventilation, the CO₂ content of arterial blood may be lowered to 10–20 mm Hg (the oxygen content of the blood is little affected), and the respiratory drive is diminished. This is why one can hold one’s breath longer after hyperventilating than without hyperventilating. This carries the risk that unconsciousness may result before the need to breathe becomes overwhelming, which is why hyperventilation is particularly dangerous before free diving.^[71]

Concentrations and role in the environment

Atmosphere

Oceans

Ocean acidification

Carbon dioxide dissolves in the ocean to form carbonic acid (H₂CO₃), bicarbonate (HCO₃⁻) and carbonate (CO₃²⁻). There is about fifty times as much carbon dioxide dissolved in the oceans as exists in the atmosphere. The oceans act as an enormous carbon sink, and have taken up about a third of CO₂ emitted by human activity.^[90]

Hydrothermal vents

Carbon dioxide is also introduced into the oceans through hydrothermal vents. The Champagne hydrothermal vent, found at the Northwest Eifuku volcano in the Mariana Trench, produces almost pure liquid carbon dioxide, one of only two known sites in the world as of 2004, the other being in the Okinawa Trough.^[94] The finding of a submarine lake of liquid carbon dioxide in the Okinawa Trough was reported in 2006.^[95]

Production

Biological processes

Carbon dioxide is a by-product of the fermentation of sugar in the brewing of beer, whisky and other alcoholic beverages and in the production of bioethanol. Yeast metabolizes sugar to produce CO₂ and ethanol, also known as alcohol, as follows:

All aerobic organisms produce CO₂ when they oxidize carbohydrates, fatty acids, and proteins. The large number of reactions involved are exceedingly complex and not described easily. Refer to (cellular respiration, anaerobic respiration and photosynthesis). The equation for the respiration of glucose and other monosaccharides is:

Anaerobic organisms decompose organic material producing methane and carbon dioxide together with traces of other compounds.^[96] Regardless of the type of organic material, the production of gases follows well defined kinetic pattern. Carbon dioxide comprises about 40–45% of the gas that emanates from decomposition in landfills (termed «landfill gas»). Most of the remaining 50–55% is methane.^[97]

Industrial processes

Carbon dioxide can be obtained by distillation from air, but the method is inefficient. Industrially, carbon dioxide is predominantly an unrecovered waste product, produced by several methods which may be practiced at various scales.^[98]

Combustion

The combustion of all carbon-based fuels, such as methane (natural gas), petroleum distillates (gasoline, diesel, kerosene, propane), coal, wood and generic organic matter produces carbon dioxide and, except in the case of pure carbon, water. As an example, the chemical reaction between methane and oxygen:

Iron is reduced from its oxides with coke in a blast furnace, producing pig iron and carbon dioxide:^[99]

By-product from hydrogen production

Carbon dioxide is a byproduct of the industrial production of hydrogen by steam reforming and the water gas shift reaction in ammonia production. These processes begin with the reaction of water and natural gas (mainly methane).^[100] This is a major source of food-grade carbon dioxide for use in carbonation of beer and soft drinks, and is also used for stunning animals such as poultry. In the summer of 2018 a shortage of carbon dioxide for these purposes arose in Europe due to the temporary shut-down of several ammonia plants for maintenance.^[101]

Thermal decomposition of limestone

It is produced by thermal decomposition of limestone, CaCO₃ by heating (calcining) at about 850 °C (1,560 °F), in the manufacture of quicklime (calcium oxide, CaO), a compound that has many industrial uses:

Acids liberate CO₂ from most metal carbonates. Consequently, it may be obtained directly from natural carbon dioxide springs, where it is produced by the action of acidified water on limestone or dolomite. The reaction between hydrochloric acid and calcium carbonate (limestone or chalk) is shown below:

The carbonic acid (H₂CO₃) then decomposes to water and CO₂:

Such reactions are accompanied by foaming or bubbling, or both, as the gas is released. They have widespread uses in industry because they can be used to neutralize waste acid streams.

Commercial uses

Carbon dioxide is used by the food industry, the oil industry, and the chemical industry.^[98]
The compound has varied commercial uses but one of its greatest uses as a chemical is in the production of carbonated beverages; it provides the sparkle in carbonated beverages such as soda water, beer and sparkling wine.

Precursor to chemicals

This section needs expansion. You can help by adding to it. (July 2014)

In the chemical industry, carbon dioxide is mainly consumed as an ingredient in the production of urea, with a smaller fraction being used to produce methanol and a range of other products.^[102] Some carboxylic acid derivatives such as sodium salicylate are prepared using CO₂ by the Kolbe–Schmitt reaction.^[103]

In addition to conventional processes using CO₂ for chemical production, electrochemical methods are also being explored at a research level. In particular, the use of renewable energy for production of fuels from CO₂ (such as methanol) is attractive as this could result in fuels that could be easily transported and used within conventional combustion technologies but have no net CO₂ emissions.^[104]

Agriculture

Plants require carbon dioxide to conduct photosynthesis. The atmospheres of greenhouses may (if of large size, must) be enriched with additional CO₂ to sustain and increase the rate of plant growth.^[105][106] At very high concentrations (100 times atmospheric concentration, or greater), carbon dioxide can be toxic to animal life, so raising the concentration to 10,000 ppm (1%) or higher for several hours will eliminate pests such as whiteflies and spider mites in a greenhouse.^[107]

Foods

Carbon dioxide is a food additive used as a propellant and acidity regulator in the food industry. It is approved for usage in the EU^[108] (listed as E number E290), US^[109] and Australia and New Zealand^[110] (listed by its INS number 290).

A candy called Pop Rocks is pressurized with carbon dioxide gas^[111] at about 4,000 kPa (40 bar; 580 psi). When placed in the mouth, it dissolves (just like other hard candy) and releases the gas bubbles with an audible pop.

Leavening agents cause dough to rise by producing carbon dioxide.^[112] Baker’s yeast produces carbon dioxide by fermentation of sugars within the dough, while chemical leaveners such as baking powder and baking soda release carbon dioxide when heated or if exposed to acids.

Beverages

Carbon dioxide is used to produce carbonated soft drinks and soda water. Traditionally, the carbonation of beer and sparkling wine came about through natural fermentation, but many manufacturers carbonate these drinks with carbon dioxide recovered from the fermentation process. In the case of bottled and kegged beer, the most common method used is carbonation with recycled carbon dioxide. With the exception of British real ale, draught beer is usually transferred from kegs in a cold room or cellar to dispensing taps on the bar using pressurized carbon dioxide, sometimes mixed with nitrogen.

The taste of soda water (and related taste sensations in other carbonated beverages) is an effect of the dissolved carbon dioxide rather than the bursting bubbles of the gas. Carbonic anhydrase 4 converts to carbonic acid leading to a sour taste, and also the dissolved carbon dioxide induces a somatosensory response.^[113]

Winemaking

Carbon dioxide in the form of dry ice is often used during the cold soak phase in winemaking to cool clusters of grapes quickly after picking to help prevent spontaneous fermentation by wild yeast. The main advantage of using dry ice over water ice is that it cools the grapes without adding any additional water that might decrease the sugar concentration in the grape must, and thus the alcohol concentration in the finished wine. Carbon dioxide is also used to create a hypoxic environment for carbonic maceration, the process used to produce Beaujolais wine.

Carbon dioxide is sometimes used to top up wine bottles or other storage vessels such as barrels to prevent oxidation, though it has the problem that it can dissolve into the wine, making a previously still wine slightly fizzy. For this reason, other gases such as nitrogen or argon are preferred for this process by professional wine makers.

Stunning animals

Carbon dioxide is often used to «stun» animals before slaughter.^[114] «Stunning» may be a misnomer, as the animals are not knocked out immediately and may suffer distress.^[115][116]

Inert gas

Carbon dioxide is one of the most commonly used compressed gases for pneumatic (pressurized gas) systems in portable pressure tools. Carbon dioxide is also used as an atmosphere for welding, although in the welding arc, it reacts to oxidize most metals. Use in the automotive industry is common despite significant evidence that welds made in carbon dioxide are more brittle than those made in more inert atmospheres.^{[citation needed]} When used for MIG welding, CO₂ use is sometimes referred to as MAG welding, for Metal Active Gas, as CO₂ can react at these high temperatures. It tends to produce a hotter puddle than truly inert atmospheres, improving the flow characteristics. Although, this may be due to atmospheric reactions occurring at the puddle site. This is usually the opposite of the desired effect when welding, as it tends to embrittle the site, but may not be a problem for general mild steel welding, where ultimate ductility is not a major concern.

Carbon dioxide is used in many consumer products that require pressurized gas because it is inexpensive and nonflammable, and because it undergoes a phase transition from gas to liquid at room temperature at an attainable pressure of approximately 60 bar (870 psi; 59 atm), allowing far more carbon dioxide to fit in a given container than otherwise would. Life jackets often contain canisters of pressured carbon dioxide for quick inflation. Aluminium capsules of CO₂ are also sold as supplies of compressed gas for air guns, paintball markers/guns, inflating bicycle tires, and for making carbonated water. High concentrations of carbon dioxide can also be used to kill pests. Liquid carbon dioxide is used in supercritical drying of some food products and technological materials, in the preparation of specimens for scanning electron microscopy^[117] and in the decaffeination of coffee beans.

Fire extinguisher

Carbon dioxide can be used to extinguish flames by flooding the environment around the flame with the gas. It does not itself react to extinguish the flame, but starves the flame of oxygen by displacing it. Some fire extinguishers, especially those designed for electrical fires, contain liquid carbon dioxide under pressure. Carbon dioxide extinguishers work well on small flammable liquid and electrical fires, but not on ordinary combustible fires, because they do not cool the burning substances significantly, and when the carbon dioxide disperses, they can catch fire upon exposure to atmospheric oxygen. They are mainly used in server rooms.^[118]

Carbon dioxide has also been widely used as an extinguishing agent in fixed fire-protection systems for local application of specific hazards and total flooding of a protected space.^[119] International Maritime Organization standards recognize carbon-dioxide systems for fire protection of ship holds and engine rooms. Carbon-dioxide-based fire-protection systems have been linked to several deaths, because it can cause suffocation in sufficiently high concentrations. A review of CO₂ systems identified 51 incidents between 1975 and the date of the report (2000), causing 72 deaths and 145 injuries.^[120]

Supercritical CO₂ as solvent

Liquid carbon dioxide is a good solvent for many lipophilic organic compounds and is used to remove caffeine from coffee.^[17] Carbon dioxide has attracted attention in the pharmaceutical and other chemical processing industries as a less toxic alternative to more traditional solvents such as organochlorides. It is also used by some dry cleaners for this reason. It is used in the preparation of some aerogels because of the properties of supercritical carbon dioxide.

Medical and pharmacological uses

In medicine, up to 5% carbon dioxide (130 times atmospheric concentration) is added to oxygen for stimulation of breathing after apnea and to stabilize the O₂/CO₂ balance in blood.

Carbon dioxide can be mixed with up to 50% oxygen, forming an inhalable gas; this is known as Carbogen and has a variety of medical and research uses.

Another medical use are the mofette, dry spas that use carbon dioxide from post-volcanic discharge for therapeutic purposes.

Energy

Supercritical CO₂ is used as the working fluid in the Allam power cycle engine.

Fossil fuel recovery

Carbon dioxide is used in enhanced oil recovery where it is injected into or adjacent to producing oil wells, usually under supercritical conditions, when it becomes miscible with the oil. This approach can increase original oil recovery by reducing residual oil saturation by 7–23% additional to primary extraction.^[121] It acts as both a pressurizing agent and, when dissolved into the underground crude oil, significantly reduces its viscosity, and changing surface chemistry enabling the oil to flow more rapidly through the reservoir to the removal well.^[122] In mature oil fields, extensive pipe networks are used to carry the carbon dioxide to the injection points.

In enhanced coal bed methane recovery, carbon dioxide would be pumped into the coal seam to displace methane, as opposed to current methods which primarily rely on the removal of water (to reduce pressure) to make the coal seam release its trapped methane.^[123]

Bio transformation into fuel

It has been proposed that CO₂ from power generation be bubbled into ponds to stimulate growth of algae that could then be converted into biodiesel fuel.^[124] A strain of the cyanobacterium Synechococcus elongatus has been genetically engineered to produce the fuels isobutyraldehyde and isobutanol from CO₂ using photosynthesis.^[125]

Researchers have developed a process called electrolysis, using enzymes isolated from bacteria to power the chemical reactions which convert CO₂ into fuels.^{[126][127][128]}

Refrigerant

Liquid and solid carbon dioxide are important refrigerants, especially in the food industry, where they are employed during the transportation and storage of ice cream and other frozen foods. Solid carbon dioxide is called «dry ice» and is used for small shipments where refrigeration equipment is not practical. Solid carbon dioxide is always below −78.5 °C (−109.3 °F) at regular atmospheric pressure, regardless of the air temperature.

Liquid carbon dioxide (industry nomenclature R744 or R-744) was used as a refrigerant prior to the use^{[citation needed]} of dichlorodifluoromethane (R12, a chlorofluorocarbon (CFC) compound). CO₂ might enjoy a renaissance because one of the main substitutes to CFCs, 1,1,1,2-tetrafluoroethane (R134a, a hydrofluorocarbon (HFC) compound) contributes to climate change more than CO₂ does. CO₂ physical properties are highly favorable for cooling, refrigeration, and heating purposes, having a high volumetric cooling capacity. Due to the need to operate at pressures of up to 130 bars (1,900 psi; 13,000 kPa), CO₂ systems require highly mechanically resistant reservoirs and components that have already been developed for mass production in many sectors. In automobile air conditioning, in more than 90% of all driving conditions for latitudes higher than 50°, CO₂ (R744) operates more efficiently than systems using HFCs (e.g., R134a). Its environmental advantages (GWP of 1, non-ozone depleting, non-toxic, non-flammable) could make it the future working fluid to replace current HFCs in cars, supermarkets, and heat pump water heaters, among others. Coca-Cola has fielded CO₂-based beverage coolers and the U.S. Army is interested in CO₂ refrigeration and heating technology.^[129][130]

Minor uses

Carbon dioxide is the lasing medium in a carbon-dioxide laser, which is one of the earliest type of lasers.

Carbon dioxide can be used as a means of controlling the pH of swimming pools,^[131] by continuously adding gas to the water, thus keeping the pH from rising. Among the advantages of this is the avoidance of handling (more hazardous) acids. Similarly, it is also used in the maintaining reef aquaria, where it is commonly used in calcium reactors to temporarily lower the pH of water being passed over calcium carbonate in order to allow the calcium carbonate to dissolve into the water more freely, where it is used by some corals to build their skeleton.

Used as the primary coolant in the British advanced gas-cooled reactor for nuclear power generation.

Carbon dioxide induction is commonly used for the euthanasia of laboratory research animals. Methods to administer CO₂ include placing animals directly into a closed, prefilled chamber containing CO₂, or exposure to a gradually increasing concentration of CO₂. The American Veterinary Medical Association’s 2020 guidelines for carbon dioxide induction state that a displacement rate of 30–70% of the chamber or cage volume per minute is optimal for the humane euthanasia of small rodents.^{[132]: 5, 31} Percentages of CO₂ vary for different species, based on identified optimal percentages to minimize distress.^[132]: 22

Carbon dioxide is also used in several related cleaning and surface-preparation techniques.

History of discovery

Carbon dioxide was the first gas to be described as a discrete substance. In about 1640,^[133] 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 sylvestris).^[134]

The properties of carbon dioxide were further studied 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.^[135]

Carbon dioxide was first liquefied (at elevated pressures) in 1823 by Humphry Davy and Michael Faraday.^[136] The earliest description of solid carbon dioxide (dry ice) was given by the French inventor 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.^[137][138]

See also

References

External links

• Current global map of carbon dioxide concentration
• CDC – NIOSH Pocket Guide to Chemical Hazards – Carbon Dioxide
• Trends in Atmospheric Carbon Dioxide (NOAA)

Carbon dioxide

Names
Other names Carbonic acid gas Carbonic anhydride Carbonic dioxide Carbon(IV) oxide R-744 (refrigerant) R744 (refrigerant alternative spelling) Dry ice (solid phase)
Identifiers
CAS Number	124-38-9
3D model (JSmol)	Interactive image Interactive image
3DMet	B01131
Beilstein Reference	1900390
ChEBI	CHEBI:16526
ChEMBL	ChEMBL1231871
ChemSpider	274
ECHA InfoCard	100.004.271
EC Number	204-696-9
E number	E290 (preservatives)
Gmelin Reference	989
KEGG	D00004
MeSH	Carbon+dioxide
PubChem CID	280
RTECS number	FF6400000
UNII	142M471B3J
UN number	1013 (gas), 1845 (solid)
CompTox Dashboard (EPA)	DTXSID4027028
InChI InChI=1S/CO2/c2-1-3  Key: CURLTUGMZLYLDI-UHFFFAOYSA-N  InChI=1/CO2/c2-1-3 Key: CURLTUGMZLYLDI-UHFFFAOYAO
SMILES O=C=O C(=O)=O
Properties
Chemical formula	CO2
Molar mass	44.009 g·mol−1
Appearance	Colorless gas
Odor	Low concentrations: none High concentrations: sharp; acidic[1]
Density	1562 kg/m3 (solid at 1 atm (100 kPa) and −78.5 °C (−109.3 °F)) 1101 kg/m3 (liquid at saturation −37 °C (−35 °F)) 1.977 kg/m3 (gas at 1 atm (100 kPa) and 0 °C (32 °F))
Critical point (T, P)	304.128(15) K[2] (30.978(15) °C), 7.3773(30) MPa[2] (72.808(30) atm)
Sublimation conditions	194.6855(30) K (−78.4645(30) °C) at 1 atm (0.101325 MPa)
Solubility in water	1.45 g/L at 25 °C (77 °F), 100 kPa (0.99 atm)
Vapor pressure	5.7292(30) MPa, 56.54(30) atm (20 °C (293.15 K))
Acidity (pKa)	6.35, 10.33
Magnetic susceptibility (χ)	−20.5·10−6 cm3/mol
Thermal conductivity	0.01662 W·m−1·K−1 (300 K (27 °C; 80 °F))[3]
Refractive index (nD)	1.00045
Viscosity	14.90 μPa·s at 25 °C (298 K)[4] 70 μPa·s at −78.5 °C (194.7 K)
Dipole moment	0 D
Structure
Crystal structure	Trigonal
Molecular shape	Linear
Thermochemistry
Heat capacity (C)	37.135 J/K·mol
Std molar entropy (S⦵298)	214 J·mol−1·K−1
Std enthalpy of formation (ΔfH⦵298)	−393.5 kJ·mol−1
Pharmacology
ATC code	V03AN02 (WHO)
Hazards
NFPA 704 (fire diamond)	[7][8] 2 0 0 SA
Lethal dose or concentration (LD, LC):
LCLo (lowest published)	90,000 ppm (human, 5 min)[6]
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 5000 ppm (9000 mg/m3)[5]
REL (Recommended)	TWA 5000 ppm (9000 mg/m3), ST 30,000 ppm (54,000 mg/m3)[5]
IDLH (Immediate danger)	40,000 ppm[5]
Safety data sheet (SDS)	Sigma-Aldrich
Related compounds
Other anions	Carbon disulfide Carbon diselenide Carbon ditelluride
Other cations	Silicon dioxide Germanium dioxide Tin dioxide Lead dioxide
Related carbon oxides	Carbon monoxide Carbon suboxide Dicarbon monoxide Carbon trioxide
Related compounds	Carbonic acid Carbonyl sulfide
Supplementary data page
Carbon dioxide (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).  verify (what is  ?) Infobox references

Carbon dioxide (chemical formula CO₂) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas. It is a trace gas in Earth’s atmosphere at 421 parts per million (ppm), or about 0.04% by volume (as of May 2022), having risen from pre-industrial levels of 280 ppm.^[9][10] Burning fossil fuels is the primary cause of these increased CO₂ concentrations and also the primary cause of climate change.^[11] Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, and seawater. When carbon dioxide dissolves in water, it forms carbonate and mainly bicarbonate (HCO⁻
₃), which causes ocean acidification as atmospheric CO₂ levels increase.^[12]

As the source of available carbon in the carbon cycle, atmospheric CO₂ is the primary carbon source for life on Earth. Its concentration in Earth’s pre-industrial atmosphere since late in the Precambrian has been regulated by organisms and geological phenomena. Plants, algae and cyanobacteria use energy from sunlight to synthesize carbohydrates from carbon dioxide and water in a process called photosynthesis, which produces oxygen as a waste product.^[13] In turn, oxygen is consumed and CO₂ is released as waste by all aerobic organisms when they metabolize organic compounds to produce energy by respiration.^[14] CO₂ is released from organic materials when they decay or combust, such as in forest fires. Since plants require CO₂ for photosynthesis, and humans and animals depend on plants for food, CO₂ is necessary for the survival of life on earth.

Carbon dioxide is 53% more dense than dry air, but is long lived and thoroughly mixes in the atmosphere. About half of excess CO₂ emissions to the atmosphere are absorbed by land and ocean carbon sinks.^[15] These sinks can become saturated and are volatile, as decay and wildfires result in the CO₂ being released back into the atmosphere.^[16] CO₂ is eventually sequestered (stored for the long term) in rocks and organic deposits like coal, petroleum and natural gas. Sequestered CO₂ is released into the atmosphere through burning fossil fuels or naturally by volcanoes, hot springs, geysers, and when carbonate rocks dissolve in water or react with acids.

CO₂ 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, and as a supercritical fluid solvent in decaffeination of coffee and supercritical drying.^[17] It is a byproduct of fermentation of sugars in bread, beer and wine making, and is added to carbonated beverages like seltzer and beer for effervescence. It has a sharp and acidic odor and generates the taste of soda water in the mouth,^[18] but at normally encountered concentrations it is odorless.^[1]

Chemical and physical properties

Structure, bonding and molecular vibrations

The symmetry of a carbon dioxide molecule is linear and centrosymmetric at its equilibrium geometry. The length of the carbon-oxygen bond in carbon dioxide is 116.3 pm, noticeably shorter than the roughly 140-pm length of a typical single C–O bond, and shorter than most other C–O multiply-bonded functional groups such as carbonyls.^[19] Since it is centrosymmetric, the molecule has no electric dipole moment.

As a linear triatomic molecule, CO₂ has four vibrational modes as shown in the diagram. In the symmetric and the antisymmetric stretching modes, the atoms move along the axis of the molecule. There are two bending modes, which are degenerate, meaning that they have the same frequency and same energy, because of the symmetry of the molecule. When a molecule touches a surface or touches another molecule, the two bending modes can differ in frequency because the interaction is different for the two modes. Some of the vibrational modes are observed in the infrared (IR) spectrum: the antisymmetric stretching mode at wavenumber 2349 cm⁻¹ (wavelength 4.25 μm) and the degenerate pair of bending modes at 667 cm⁻¹ (wavelength 15 μm). The symmetric stretching mode does not create an electric dipole so is not observed in IR spectroscopy, but it is detected in by Raman spectroscopy at 1388 cm⁻¹ (wavelength 7.2 μm).^[20]

In the gas phase, carbon dioxide molecules undergo significant vibrational motions and do not keep a fixed structure. However, in a Coulomb explosion imaging experiment, an instantaneous image of the molecular structure can be deduced. Such an experiment^[21] has been performed for carbon dioxide.
The result of this experiment, and the conclusion of theoretical calculations^[22] based on an ab initio potential energy surface of the molecule, is that none of the
molecules in the gas phase are ever exactly linear. This counter-intuitive result is trivially due to
the fact that the nuclear motion volume element vanishes for linear geometries.^[22]
This is so for all molecules (except diatomics!).

In aqueous solution

Carbon dioxide is soluble in water, in which it reversibly forms H₂CO₃ (carbonic acid), which is a weak acid since its ionization in water is incomplete.

The hydration equilibrium constant of carbonic acid is, at 25 °C:

Hence, the majority of the carbon dioxide is not converted into carbonic acid, but remains as CO₂ molecules, not affecting the pH.

The relative concentrations of CO₂, H₂CO₃, and the deprotonated forms HCO−3 (bicarbonate) and CO2−3(carbonate) depend on the pH. As shown in a Bjerrum plot, in neutral or slightly alkaline water (pH > 6.5), the bicarbonate form predominates (>50%) becoming the most prevalent (>95%) at the pH of seawater. In very alkaline water (pH > 10.4), the predominant (>50%) form is carbonate. The oceans, being mildly alkaline with typical pH = 8.2–8.5, contain about 120 mg of bicarbonate per liter.

Being diprotic, carbonic acid has two acid dissociation constants, the first one for the dissociation into the bicarbonate (also called hydrogen carbonate) ion (HCO−3):

K_a1 = 2.5×10⁻⁴ mol/L; pK_a1 = 3.6 at 25 °C.^[19]

This is the true first acid dissociation constant, defined as

where the denominator includes only covalently bound H₂CO₃ and does not include hydrated CO_2(aq). The much smaller and often-quoted value near 4.16×10⁻⁷ is an apparent value calculated on the (incorrect) assumption that all dissolved CO₂ is present as carbonic acid, so that

Since most of the dissolved CO₂remains as CO₂ molecules, K_a1(apparent) has a much larger denominator and a much smaller value than the true K_a1.^[23]

The bicarbonate ion is an amphoteric species that can act as an acid or as a base, depending on pH of the solution. At high pH, it dissociates significantly into the carbonate ion (CO2−3):

K_a2 = 4.69×10⁻¹¹ mol/L; pK_a2 = 10.329

In organisms carbonic acid production is catalysed by the enzyme, carbonic anhydrase.

Chemical reactions of CO₂

CO₂ is a potent electrophile having an electrophilic reactivity that is comparable to benzaldehyde or strong α,β-unsaturated carbonyl compounds. However, unlike electrophiles of similar reactivity, the reactions of nucleophiles with CO₂ are thermodynamically less favored and are often found to be highly reversible.^[24] Only very strong nucleophiles, like the carbanions provided by Grignard reagents and organolithium compounds react with CO₂ to give carboxylates:

where M = Li or Mg Br and R = alkyl or aryl.

In metal carbon dioxide complexes, CO₂ serves as a ligand, which can facilitate the conversion of CO₂ to other chemicals.^[25]

The reduction of CO₂ to CO is ordinarily a difficult and slow reaction:

Photoautotrophs (i.e. plants and cyanobacteria) use the energy contained in sunlight to photosynthesize simple sugars from CO₂ absorbed from the air and water:

The redox potential for this reaction near pH 7 is about −0.53 V versus the standard hydrogen electrode. The nickel-containing enzyme carbon monoxide dehydrogenase catalyses this process.^[26]

Physical properties

Carbon dioxide is colorless. At low concentrations the gas is odorless; however, at sufficiently high concentrations, it has a sharp, acidic odor.^[1] At standard temperature and pressure, the density of carbon dioxide is around 1.98 kg/m³, about 1.53 times that of air.^[27]

Carbon dioxide has no liquid state at pressures below 0.51795(10) MPa^[2] (5.11177(99) atm). At a pressure of 1 atm (0.101325 MPa), the gas deposits directly to a solid at temperatures below 194.6855(30) K^[2] (−78.4645(30) °C) and the solid sublimes directly to a gas above this temperature. In its solid state, carbon dioxide is commonly called dry ice.

Liquid carbon dioxide forms only at pressures above 0.51795(10) MPa^[2] (5.11177(99) atm); the triple point of carbon dioxide is 216.592(3) K^[2] (−56.558(3) °C) at 0.51795(10) MPa^[2] (5.11177(99) atm) (see phase diagram). The critical point is 304.128(15) K^[2] (30.978(15) °C) at 7.3773(30) MPa^[2] (72.808(30) atm). Another form of solid carbon dioxide observed at high pressure is an amorphous glass-like solid.^[28] This form of glass, called carbonia, is produced by supercooling heated CO₂ at extreme pressures (40–48 GPa, or about 400,000 atmospheres) in a diamond anvil. This discovery confirmed the theory that carbon dioxide could exist in a glass state similar to other members of its elemental family, like silicon dioxide (silica glass) and germanium dioxide. Unlike silica and germania glasses, however, carbonia glass is not stable at normal pressures and reverts to gas when pressure is released.

At temperatures and pressures above the critical point, carbon dioxide behaves as a supercritical fluid known as supercritical carbon dioxide.

Table of thermal and physical properties of saturated liquid carbon dioxide:^[29][30]

Temperature (°C)	Density (kg/m^3)	Specific heat (kJ/kg K)	Kinematic viscosity (m^2/s)	Conductivity (W/m K)	Thermal diffusivity (m^2/s)	Prandtl Number	Bulk modulus (K^-1)
-50	1156.34	1.84	1.19E-07	0.0855	4.02E-08	2.96	—
-40	1117.77	1.88	1.18E-07	0.1011	4.81E-08	2.46	—
-30	1076.76	1.97	1.17E-07	0.1116	5.27E-08	2.22	—
-20	1032.39	2.05	1.15E-07	0.1151	5.45E-08	2.12	—
-10	983.38	2.18	1.13E-07	0.1099	5.13E-08	2.2	—
0	926.99	2.47	1.08E-07	0.1045	4.58E-08	2.38	—
10	860.03	3.14	1.01E-07	0.0971	3.61E-08	2.8	—
20	772.57	5	9.10E-08	0.0872	2.22E-08	4.1	1.40E-02
30	597.81	36.4	8.00E-08	0.0703	0.279E-08	28.7	—

Table of thermal and physical properties of carbon dioxide (CO2) at atmospheric pressure:^[29][30]

Temperature (K)	Density (kg/m^3)	Specific heat (kJ/kg °C)	Dynamic viscosity (kg/m s)	Kinematic viscosity (m^2/s)	Thermal conductivity (W/m °C)	Thermal diffusivity (m^2/s)	Prandtl Number
220	2.4733	0.783	1.11E-05	4.49E-06	0.010805	5.92E-06	0.818
250	2.1657	0.804	1.26E-05	5.81E-06	0.012884	7.40E-06	0.793
300	1.7973	0.871	1.50E-05	8.32E-06	0.016572	1.06E-05	0.77
350	1.5362	0.9	1.72E-05	1.12E-05	0.02047	1.48E-05	0.755
400	1.3424	0.942	1.93E-05	1.44E-05	0.02461	1.95E-05	0.738
450	1.1918	0.98	2.13E-05	1.79E-05	0.02897	2.48E-05	0.721
500	1.0732	1.013	2.33E-05	2.17E-05	0.03352	3.08E-05	0.702
550	0.9739	1.047	2.51E-05	2.57E-05	0.03821	3.75E-05	0.685
600	0.8938	1.076	2.68E-05	3.00E-05	0.04311	4.48E-05	0.668
650	0.8143	1.1	2.88E-05	3.54E-05	0.0445	4.97E-05	0.712
700	0.7564	1.13E+00	3.05E-05	4.03E-05	0.0481	5.63E-05	0.717
750	0.7057	1.15	3.21E-05	4.55E-05	0.0517	6.37E-05	0.714
800	0.6614	1.17E+00	3.37E-05	5.10E-05	0.0551	7.12E-05	0.716

Biological role

Carbon dioxide is an end product of cellular respiration in organisms that obtain energy by breaking down sugars, fats and amino acids with oxygen as part of their metabolism. This includes all plants, algae and animals and aerobic fungi and bacteria. In vertebrates, the carbon dioxide travels in the blood from the body’s tissues to the skin (e.g., amphibians) or the gills (e.g., fish), from where it dissolves in the water, or to the lungs from where it is exhaled. During active photosynthesis, plants can absorb more carbon dioxide from the atmosphere than they release in respiration.

Photosynthesis and carbon fixation

Carbon fixation is a biochemical process by which atmospheric carbon dioxide is incorporated by plants, algae and (cyanobacteria) into energy-rich organic molecules such as glucose, thus creating their own food by photosynthesis. Photosynthesis uses carbon dioxide and water to produce sugars from which other organic compounds can be constructed, and oxygen is produced as a by-product.

Ribulose-1,5-bisphosphate carboxylase oxygenase, commonly abbreviated to RuBisCO, is the enzyme involved in the first major step of carbon fixation, the production of two molecules of 3-phosphoglycerate from CO₂ and ribulose bisphosphate, as shown in the diagram at left.

RuBisCO is thought to be the single most abundant protein on Earth.^[31]

Phototrophs use the products of their photosynthesis as internal food sources and as raw material for the biosynthesis of more complex organic molecules, such as polysaccharides, nucleic acids and proteins. These are used for their own growth, and also as the basis of the food chains and webs that feed other organisms, including animals such as ourselves. Some important phototrophs, the coccolithophores synthesise hard calcium carbonate scales.^[32] A globally significant species of coccolithophore is Emiliania huxleyi whose calcite scales have formed the basis of many sedimentary rocks such as limestone, where what was previously atmospheric carbon can remain fixed for geological timescales.

Plants can grow as much as 50 percent faster in concentrations of 1,000 ppm CO₂ when compared with ambient conditions, though this assumes no change in climate and no limitation on other nutrients.^[33] Elevated CO₂ levels cause increased growth reflected in the harvestable yield of crops, with wheat, rice and soybean all showing increases in yield of 12–14% under elevated CO₂ in FACE experiments.^[34][35]

Increased atmospheric CO₂ concentrations result in fewer stomata developing on plants^[36] which leads to reduced water usage and increased water-use efficiency.^[37] Studies using FACE have shown that CO₂ enrichment leads to decreased concentrations of micronutrients in crop plants.^[38] This may have knock-on effects on other parts of ecosystems as herbivores will need to eat more food to gain the same amount of protein.^[39]

The concentration of secondary metabolites such as phenylpropanoids and flavonoids can also be altered in plants exposed to high concentrations of CO₂.^[40][41]

Plants also emit CO₂ during respiration, and so the majority of plants and algae, which use C3 photosynthesis, are only net absorbers during the day. Though a growing forest will absorb many tons of CO₂ each year, a mature forest will produce as much CO₂ from respiration and decomposition of dead specimens (e.g., fallen branches) as is used in photosynthesis in growing plants.^[42] Contrary to the long-standing view that they are carbon neutral, mature forests can continue to accumulate carbon^[43] and remain valuable carbon sinks, helping to maintain the carbon balance of Earth’s atmosphere. Additionally, and crucially to life on earth, photosynthesis by phytoplankton consumes dissolved CO₂ in the upper ocean and thereby promotes the absorption of CO₂ from the atmosphere.^[44]

Toxicity

Carbon dioxide content in fresh air (averaged between sea-level and 10 kPa level, i.e., about 30 km (19 mi) altitude) varies between 0.036% (360 ppm) and 0.041% (412 ppm), depending on the location.^{[46][clarification needed]}

CO₂ is an asphyxiant gas and not classified as toxic or harmful in accordance with Globally Harmonized System of Classification and Labelling of Chemicals standards of United Nations Economic Commission for Europe by using the OECD Guidelines for the Testing of Chemicals. In concentrations up to 1% (10,000 ppm), it will make some people feel drowsy and give the lungs a stuffy feeling.^[45] Concentrations of 7% to 10% (70,000 to 100,000 ppm) may cause suffocation, even in the presence of sufficient oxygen, manifesting as dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour.^[47] The physiological effects of acute carbon dioxide exposure are grouped together under the term hypercapnia, a subset of asphyxiation.

Because it is heavier than air, in locations where the gas seeps from the ground (due to sub-surface volcanic or geothermal activity) in relatively high concentrations, without the dispersing effects of wind, it can collect in sheltered/pocketed locations below average ground level, causing animals located therein to be suffocated. Carrion feeders attracted to the carcasses are then also killed. Children have been killed in the same way near the city of Goma by CO₂ emissions from the nearby volcano Mount Nyiragongo.^[48] The Swahili term for this phenomenon is mazuku.

Adaptation to increased concentrations of CO₂ occurs in humans, including modified breathing and kidney bicarbonate production, in order to balance the effects of blood acidification (acidosis). Several studies suggested that 2.0 percent inspired concentrations could be used for closed air spaces (e.g. a submarine) since the adaptation is physiological and reversible, as deterioration in performance or in normal physical activity does not happen at this level of exposure for five days.^[49][50] Yet, other studies show a decrease in cognitive function even at much lower levels.^[51][52] Also, with ongoing respiratory acidosis, adaptation or compensatory mechanisms will be unable to reverse such condition.

Below 1%

There are few studies of the health effects of long-term continuous CO₂ exposure on humans and animals at levels below 1%. Occupational CO₂ exposure limits have been set in the United States at 0.5% (5000 ppm) for an eight-hour period.^[53] At this CO₂ concentration, International Space Station crew experienced headaches, lethargy, mental slowness, emotional irritation, and sleep disruption.^[54] Studies in animals at 0.5% CO₂ have demonstrated kidney calcification and bone loss after eight weeks of exposure.^[55] A study of humans exposed in 2.5 hour sessions demonstrated significant negative effects on cognitive abilities at concentrations as low as 0.1% (1000 ppm) CO₂ likely due to CO₂ induced increases in cerebral blood flow.^[51] Another study observed a decline in basic activity level and information usage at 1000 ppm, when compared to 500 ppm.^[52] However a review of the literature found that most studies on the phenomenon of carbon dioxide induced cognitive impairment to have a small effect on high-level decision making and most of the studies were confounded by inadequate study designs, environmental comfort, uncertainties in exposure doses and differing cognitive assessments used.^[56] Similarly a study on the effects of the concentration of CO₂ in motorcycle helmets has been criticized for having dubious methodology in not noting the self-reports of motorcycle riders and taking measurements using mannequins. Further when normal motorcycle conditions were achieved (such as highway or city speeds) or the visor was raised the concentration of CO₂ declined to safe levels (0.2%).^[57][58]

Ventilation

Poor ventilation is one of the main causes of excessive CO₂ concentrations in closed spaces, leading to poor indoor air quality. Carbon dioxide differential above outdoor concentrations at steady state conditions (when the occupancy and ventilation system operation are sufficiently long that CO₂ concentration has stabilized) are sometimes used to estimate ventilation rates per person.^{[citation needed]} Higher CO₂ concentrations are associated with occupant health, comfort and performance degradation.^[59][60] ASHRAE Standard 62.1–2007 ventilation rates may result in indoor concentrations up to 2,100 ppm above ambient outdoor conditions. Thus if the outdoor concentration is 400 ppm, indoor concentrations may reach 2,500 ppm with ventilation rates that meet this industry consensus standard. Concentrations in poorly ventilated spaces can be found even higher than this (range of 3,000 or 4,000 ppm).

Miners, who are particularly vulnerable to gas exposure due to insufficient ventilation, referred to mixtures of carbon dioxide and nitrogen as «blackdamp», «choke damp» or «stythe». Before more effective technologies were developed, miners would frequently monitor for dangerous levels of blackdamp and other gases in mine shafts by bringing a caged canary with them as they worked. The canary is more sensitive to asphyxiant gases than humans, and as it became unconscious would stop singing and fall off its perch. The Davy lamp could also detect high levels of blackdamp (which sinks, and collects near the floor) by burning less brightly, while methane, another suffocating gas and explosion risk, would make the lamp burn more brightly.

In February 2020, three people died from suffocation at a party in Moscow when dry ice (frozen CO₂) was added to a swimming pool to cool it down.^[61] A similar accident occurred in 2018 when a woman died from CO₂ fumes emanating from the large amount of dry ice she was transporting in her car.^[62]

Outdoor areas with elevated concentrations

Local concentrations of carbon dioxide can reach high values near strong sources, especially those that are isolated by surrounding terrain. At the Bossoleto hot spring near Rapolano Terme in Tuscany, Italy, situated in a bowl-shaped depression about 100 m (330 ft) in diameter, concentrations of CO₂ rise to above 75% overnight, sufficient to kill insects and small animals. After sunrise the gas is dispersed by convection.^[63] High concentrations of CO₂ produced by disturbance of deep lake water saturated with CO₂ are thought to have caused 37 fatalities at Lake Monoun, Cameroon in 1984 and 1700 casualties at Lake Nyos, Cameroon in 1986.^[64]

Human physiology

Content

Reference ranges or averages for partial pressures of carbon dioxide (abbreviated pCO₂)

Blood compartment	(kPa)	(mm Hg)
Venous blood carbon dioxide	5.5–6.8	41–51[65]	41–51[65]
Alveolar pulmonary gas pressures	4.8	36	36
Arterial blood carbon dioxide	4.7–6.0	35–45[65]	35–45[65]

The body produces approximately 2.3 pounds (1.0 kg) of carbon dioxide per day per person,^[66] containing 0.63 pounds (290 g) of carbon. In humans, this carbon dioxide is carried through the venous system and is breathed out through the lungs, resulting in lower concentrations in the arteries. The carbon dioxide content of the blood is often given as the partial pressure, which is the pressure which carbon dioxide would have had if it alone occupied the volume.^[67] In humans, the blood carbon dioxide contents is shown in the adjacent table.

Transport in the blood

CO₂ is carried in blood in three different ways. (Exact percentages vary between arterial and venous blood).

• Majority (about 70% to 80%) is converted to bicarbonate ions HCO−3 by the enzyme carbonic anhydrase in the red blood cells,^[68] by the reaction CO₂ + H₂O → H₂CO₃ → H⁺ + HCO−3.
• 5–10% is dissolved in blood plasma^[68]
• 5–10% is bound to hemoglobin as carbamino compounds^[68]

Hemoglobin, the main oxygen-carrying molecule in red blood cells, carries both oxygen and carbon dioxide. However, the CO₂ bound to hemoglobin does not bind to the same site as oxygen. Instead, it combines with the N-terminal groups on the four globin chains. However, because of allosteric effects on the hemoglobin molecule, the binding of CO₂ decreases the amount of oxygen that is bound for a given partial pressure of oxygen. This is known as the Haldane Effect, and is important in the transport of carbon dioxide from the tissues to the lungs. Conversely, a rise in the partial pressure of CO₂ or a lower pH will cause offloading of oxygen from hemoglobin, which is known as the Bohr effect.

Regulation of respiration

Carbon dioxide is one of the mediators of local autoregulation of blood supply. If its concentration is high, the capillaries expand to allow a greater blood flow to that tissue.^[69]

Bicarbonate ions are crucial for regulating blood pH. A person’s breathing rate influences the level of CO₂ in their blood. Breathing that is too slow or shallow causes respiratory acidosis, while breathing that is too rapid leads to hyperventilation, which can cause respiratory alkalosis.^[70]

Although the body requires oxygen for metabolism, low oxygen levels normally do not stimulate breathing. Rather, breathing is stimulated by higher carbon dioxide levels. As a result, breathing low-pressure air or a gas mixture with no oxygen at all (such as pure nitrogen) can lead to loss of consciousness without ever experiencing air hunger. This is especially perilous for high-altitude fighter pilots. It is also why flight attendants instruct passengers, in case of loss of cabin pressure, to apply the oxygen mask to themselves first before helping others; otherwise, one risks losing consciousness.^[68]

The respiratory centers try to maintain an arterial CO₂ pressure of 40 mm Hg. With intentional hyperventilation, the CO₂ content of arterial blood may be lowered to 10–20 mm Hg (the oxygen content of the blood is little affected), and the respiratory drive is diminished. This is why one can hold one’s breath longer after hyperventilating than without hyperventilating. This carries the risk that unconsciousness may result before the need to breathe becomes overwhelming, which is why hyperventilation is particularly dangerous before free diving.^[71]

Concentrations and role in the environment

Atmosphere

Oceans

Ocean acidification

Carbon dioxide dissolves in the ocean to form carbonic acid (H₂CO₃), bicarbonate (HCO₃⁻) and carbonate (CO₃²⁻). There is about fifty times as much carbon dioxide dissolved in the oceans as exists in the atmosphere. The oceans act as an enormous carbon sink, and have taken up about a third of CO₂ emitted by human activity.^[90]

Hydrothermal vents

Carbon dioxide is also introduced into the oceans through hydrothermal vents. The Champagne hydrothermal vent, found at the Northwest Eifuku volcano in the Mariana Trench, produces almost pure liquid carbon dioxide, one of only two known sites in the world as of 2004, the other being in the Okinawa Trough.^[94] The finding of a submarine lake of liquid carbon dioxide in the Okinawa Trough was reported in 2006.^[95]

Production

Biological processes

Carbon dioxide is a by-product of the fermentation of sugar in the brewing of beer, whisky and other alcoholic beverages and in the production of bioethanol. Yeast metabolizes sugar to produce CO₂ and ethanol, also known as alcohol, as follows:

All aerobic organisms produce CO₂ when they oxidize carbohydrates, fatty acids, and proteins. The large number of reactions involved are exceedingly complex and not described easily. Refer to (cellular respiration, anaerobic respiration and photosynthesis). The equation for the respiration of glucose and other monosaccharides is:

Anaerobic organisms decompose organic material producing methane and carbon dioxide together with traces of other compounds.^[96] Regardless of the type of organic material, the production of gases follows well defined kinetic pattern. Carbon dioxide comprises about 40–45% of the gas that emanates from decomposition in landfills (termed «landfill gas»). Most of the remaining 50–55% is methane.^[97]

Industrial processes

Carbon dioxide can be obtained by distillation from air, but the method is inefficient. Industrially, carbon dioxide is predominantly an unrecovered waste product, produced by several methods which may be practiced at various scales.^[98]

Combustion

The combustion of all carbon-based fuels, such as methane (natural gas), petroleum distillates (gasoline, diesel, kerosene, propane), coal, wood and generic organic matter produces carbon dioxide and, except in the case of pure carbon, water. As an example, the chemical reaction between methane and oxygen:

Iron is reduced from its oxides with coke in a blast furnace, producing pig iron and carbon dioxide:^[99]

By-product from hydrogen production

Carbon dioxide is a byproduct of the industrial production of hydrogen by steam reforming and the water gas shift reaction in ammonia production. These processes begin with the reaction of water and natural gas (mainly methane).^[100] This is a major source of food-grade carbon dioxide for use in carbonation of beer and soft drinks, and is also used for stunning animals such as poultry. In the summer of 2018 a shortage of carbon dioxide for these purposes arose in Europe due to the temporary shut-down of several ammonia plants for maintenance.^[101]

Thermal decomposition of limestone

It is produced by thermal decomposition of limestone, CaCO₃ by heating (calcining) at about 850 °C (1,560 °F), in the manufacture of quicklime (calcium oxide, CaO), a compound that has many industrial uses:

Acids liberate CO₂ from most metal carbonates. Consequently, it may be obtained directly from natural carbon dioxide springs, where it is produced by the action of acidified water on limestone or dolomite. The reaction between hydrochloric acid and calcium carbonate (limestone or chalk) is shown below:

The carbonic acid (H₂CO₃) then decomposes to water and CO₂:

Such reactions are accompanied by foaming or bubbling, or both, as the gas is released. They have widespread uses in industry because they can be used to neutralize waste acid streams.

Commercial uses

Carbon dioxide is used by the food industry, the oil industry, and the chemical industry.^[98]
The compound has varied commercial uses but one of its greatest uses as a chemical is in the production of carbonated beverages; it provides the sparkle in carbonated beverages such as soda water, beer and sparkling wine.

Precursor to chemicals

This section needs expansion. You can help by adding to it. (July 2014)

In the chemical industry, carbon dioxide is mainly consumed as an ingredient in the production of urea, with a smaller fraction being used to produce methanol and a range of other products.^[102] Some carboxylic acid derivatives such as sodium salicylate are prepared using CO₂ by the Kolbe–Schmitt reaction.^[103]

In addition to conventional processes using CO₂ for chemical production, electrochemical methods are also being explored at a research level. In particular, the use of renewable energy for production of fuels from CO₂ (such as methanol) is attractive as this could result in fuels that could be easily transported and used within conventional combustion technologies but have no net CO₂ emissions.^[104]

Agriculture

Plants require carbon dioxide to conduct photosynthesis. The atmospheres of greenhouses may (if of large size, must) be enriched with additional CO₂ to sustain and increase the rate of plant growth.^[105][106] At very high concentrations (100 times atmospheric concentration, or greater), carbon dioxide can be toxic to animal life, so raising the concentration to 10,000 ppm (1%) or higher for several hours will eliminate pests such as whiteflies and spider mites in a greenhouse.^[107]

Foods

Carbon dioxide is a food additive used as a propellant and acidity regulator in the food industry. It is approved for usage in the EU^[108] (listed as E number E290), US^[109] and Australia and New Zealand^[110] (listed by its INS number 290).

A candy called Pop Rocks is pressurized with carbon dioxide gas^[111] at about 4,000 kPa (40 bar; 580 psi). When placed in the mouth, it dissolves (just like other hard candy) and releases the gas bubbles with an audible pop.

Leavening agents cause dough to rise by producing carbon dioxide.^[112] Baker’s yeast produces carbon dioxide by fermentation of sugars within the dough, while chemical leaveners such as baking powder and baking soda release carbon dioxide when heated or if exposed to acids.

Beverages

Carbon dioxide is used to produce carbonated soft drinks and soda water. Traditionally, the carbonation of beer and sparkling wine came about through natural fermentation, but many manufacturers carbonate these drinks with carbon dioxide recovered from the fermentation process. In the case of bottled and kegged beer, the most common method used is carbonation with recycled carbon dioxide. With the exception of British real ale, draught beer is usually transferred from kegs in a cold room or cellar to dispensing taps on the bar using pressurized carbon dioxide, sometimes mixed with nitrogen.

The taste of soda water (and related taste sensations in other carbonated beverages) is an effect of the dissolved carbon dioxide rather than the bursting bubbles of the gas. Carbonic anhydrase 4 converts to carbonic acid leading to a sour taste, and also the dissolved carbon dioxide induces a somatosensory response.^[113]

Winemaking

Carbon dioxide in the form of dry ice is often used during the cold soak phase in winemaking to cool clusters of grapes quickly after picking to help prevent spontaneous fermentation by wild yeast. The main advantage of using dry ice over water ice is that it cools the grapes without adding any additional water that might decrease the sugar concentration in the grape must, and thus the alcohol concentration in the finished wine. Carbon dioxide is also used to create a hypoxic environment for carbonic maceration, the process used to produce Beaujolais wine.

Carbon dioxide is sometimes used to top up wine bottles or other storage vessels such as barrels to prevent oxidation, though it has the problem that it can dissolve into the wine, making a previously still wine slightly fizzy. For this reason, other gases such as nitrogen or argon are preferred for this process by professional wine makers.

Stunning animals

Carbon dioxide is often used to «stun» animals before slaughter.^[114] «Stunning» may be a misnomer, as the animals are not knocked out immediately and may suffer distress.^[115][116]

Inert gas

Carbon dioxide is one of the most commonly used compressed gases for pneumatic (pressurized gas) systems in portable pressure tools. Carbon dioxide is also used as an atmosphere for welding, although in the welding arc, it reacts to oxidize most metals. Use in the automotive industry is common despite significant evidence that welds made in carbon dioxide are more brittle than those made in more inert atmospheres.^{[citation needed]} When used for MIG welding, CO₂ use is sometimes referred to as MAG welding, for Metal Active Gas, as CO₂ can react at these high temperatures. It tends to produce a hotter puddle than truly inert atmospheres, improving the flow characteristics. Although, this may be due to atmospheric reactions occurring at the puddle site. This is usually the opposite of the desired effect when welding, as it tends to embrittle the site, but may not be a problem for general mild steel welding, where ultimate ductility is not a major concern.

Carbon dioxide is used in many consumer products that require pressurized gas because it is inexpensive and nonflammable, and because it undergoes a phase transition from gas to liquid at room temperature at an attainable pressure of approximately 60 bar (870 psi; 59 atm), allowing far more carbon dioxide to fit in a given container than otherwise would. Life jackets often contain canisters of pressured carbon dioxide for quick inflation. Aluminium capsules of CO₂ are also sold as supplies of compressed gas for air guns, paintball markers/guns, inflating bicycle tires, and for making carbonated water. High concentrations of carbon dioxide can also be used to kill pests. Liquid carbon dioxide is used in supercritical drying of some food products and technological materials, in the preparation of specimens for scanning electron microscopy^[117] and in the decaffeination of coffee beans.

Fire extinguisher

Carbon dioxide can be used to extinguish flames by flooding the environment around the flame with the gas. It does not itself react to extinguish the flame, but starves the flame of oxygen by displacing it. Some fire extinguishers, especially those designed for electrical fires, contain liquid carbon dioxide under pressure. Carbon dioxide extinguishers work well on small flammable liquid and electrical fires, but not on ordinary combustible fires, because they do not cool the burning substances significantly, and when the carbon dioxide disperses, they can catch fire upon exposure to atmospheric oxygen. They are mainly used in server rooms.^[118]

Carbon dioxide has also been widely used as an extinguishing agent in fixed fire-protection systems for local application of specific hazards and total flooding of a protected space.^[119] International Maritime Organization standards recognize carbon-dioxide systems for fire protection of ship holds and engine rooms. Carbon-dioxide-based fire-protection systems have been linked to several deaths, because it can cause suffocation in sufficiently high concentrations. A review of CO₂ systems identified 51 incidents between 1975 and the date of the report (2000), causing 72 deaths and 145 injuries.^[120]

Supercritical CO₂ as solvent

Liquid carbon dioxide is a good solvent for many lipophilic organic compounds and is used to remove caffeine from coffee.^[17] Carbon dioxide has attracted attention in the pharmaceutical and other chemical processing industries as a less toxic alternative to more traditional solvents such as organochlorides. It is also used by some dry cleaners for this reason. It is used in the preparation of some aerogels because of the properties of supercritical carbon dioxide.

Medical and pharmacological uses

In medicine, up to 5% carbon dioxide (130 times atmospheric concentration) is added to oxygen for stimulation of breathing after apnea and to stabilize the O₂/CO₂ balance in blood.

Carbon dioxide can be mixed with up to 50% oxygen, forming an inhalable gas; this is known as Carbogen and has a variety of medical and research uses.

Another medical use are the mofette, dry spas that use carbon dioxide from post-volcanic discharge for therapeutic purposes.

Energy

Supercritical CO₂ is used as the working fluid in the Allam power cycle engine.

Fossil fuel recovery

Carbon dioxide is used in enhanced oil recovery where it is injected into or adjacent to producing oil wells, usually under supercritical conditions, when it becomes miscible with the oil. This approach can increase original oil recovery by reducing residual oil saturation by 7–23% additional to primary extraction.^[121] It acts as both a pressurizing agent and, when dissolved into the underground crude oil, significantly reduces its viscosity, and changing surface chemistry enabling the oil to flow more rapidly through the reservoir to the removal well.^[122] In mature oil fields, extensive pipe networks are used to carry the carbon dioxide to the injection points.

In enhanced coal bed methane recovery, carbon dioxide would be pumped into the coal seam to displace methane, as opposed to current methods which primarily rely on the removal of water (to reduce pressure) to make the coal seam release its trapped methane.^[123]

Bio transformation into fuel

It has been proposed that CO₂ from power generation be bubbled into ponds to stimulate growth of algae that could then be converted into biodiesel fuel.^[124] A strain of the cyanobacterium Synechococcus elongatus has been genetically engineered to produce the fuels isobutyraldehyde and isobutanol from CO₂ using photosynthesis.^[125]

Researchers have developed a process called electrolysis, using enzymes isolated from bacteria to power the chemical reactions which convert CO₂ into fuels.^{[126][127][128]}

Refrigerant

Liquid and solid carbon dioxide are important refrigerants, especially in the food industry, where they are employed during the transportation and storage of ice cream and other frozen foods. Solid carbon dioxide is called «dry ice» and is used for small shipments where refrigeration equipment is not practical. Solid carbon dioxide is always below −78.5 °C (−109.3 °F) at regular atmospheric pressure, regardless of the air temperature.

Liquid carbon dioxide (industry nomenclature R744 or R-744) was used as a refrigerant prior to the use^{[citation needed]} of dichlorodifluoromethane (R12, a chlorofluorocarbon (CFC) compound). CO₂ might enjoy a renaissance because one of the main substitutes to CFCs, 1,1,1,2-tetrafluoroethane (R134a, a hydrofluorocarbon (HFC) compound) contributes to climate change more than CO₂ does. CO₂ physical properties are highly favorable for cooling, refrigeration, and heating purposes, having a high volumetric cooling capacity. Due to the need to operate at pressures of up to 130 bars (1,900 psi; 13,000 kPa), CO₂ systems require highly mechanically resistant reservoirs and components that have already been developed for mass production in many sectors. In automobile air conditioning, in more than 90% of all driving conditions for latitudes higher than 50°, CO₂ (R744) operates more efficiently than systems using HFCs (e.g., R134a). Its environmental advantages (GWP of 1, non-ozone depleting, non-toxic, non-flammable) could make it the future working fluid to replace current HFCs in cars, supermarkets, and heat pump water heaters, among others. Coca-Cola has fielded CO₂-based beverage coolers and the U.S. Army is interested in CO₂ refrigeration and heating technology.^[129][130]

Minor uses

Carbon dioxide is the lasing medium in a carbon-dioxide laser, which is one of the earliest type of lasers.

Carbon dioxide can be used as a means of controlling the pH of swimming pools,^[131] by continuously adding gas to the water, thus keeping the pH from rising. Among the advantages of this is the avoidance of handling (more hazardous) acids. Similarly, it is also used in the maintaining reef aquaria, where it is commonly used in calcium reactors to temporarily lower the pH of water being passed over calcium carbonate in order to allow the calcium carbonate to dissolve into the water more freely, where it is used by some corals to build their skeleton.

Used as the primary coolant in the British advanced gas-cooled reactor for nuclear power generation.

Carbon dioxide induction is commonly used for the euthanasia of laboratory research animals. Methods to administer CO₂ include placing animals directly into a closed, prefilled chamber containing CO₂, or exposure to a gradually increasing concentration of CO₂. The American Veterinary Medical Association’s 2020 guidelines for carbon dioxide induction state that a displacement rate of 30–70% of the chamber or cage volume per minute is optimal for the humane euthanasia of small rodents.^{[132]: 5, 31} Percentages of CO₂ vary for different species, based on identified optimal percentages to minimize distress.^[132]: 22

Carbon dioxide is also used in several related cleaning and surface-preparation techniques.

History of discovery

Carbon dioxide was the first gas to be described as a discrete substance. In about 1640,^[133] 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 sylvestris).^[134]

The properties of carbon dioxide were further studied 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.^[135]

Carbon dioxide was first liquefied (at elevated pressures) in 1823 by Humphry Davy and Michael Faraday.^[136] The earliest description of solid carbon dioxide (dry ice) was given by the French inventor 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.^[137][138]

See also

References

External links

• Current global map of carbon dioxide concentration
• CDC – NIOSH Pocket Guide to Chemical Hazards – Carbon Dioxide
• Trends in Atmospheric Carbon Dioxide (NOAA)

Значение слова «Углерод»

— химический элемент, важнейшая составная часть всех органических веществ в природе

Транскрипция слова

[угл’иро́т]

MFA Международная транскрипция

[ʊɡlʲɪˈrot]

у	[у]	гласный, безударный
г	[г]	согласный, звонкий парный, твердый парный
л	[л’]	согласный, звонкий непарный (сонорный), мягкий парный
е	[и]	гласный, безударный
р	[р]	согласный, звонкий непарный (сонорный), твердый парный
о	[́о]	гласный, ударный
д	[т]	согласный, глухой парный, твердый парный

Букв: 7 Звуков: 7

Цветовая схема слова

углерод

Как произносится слово «Углерод»

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Как правильно пишется «Углерод»

углеро́д

углеро́д, -а

Как правильно перенести «Углерод»

уг—ле—ро́д

Часть речи

Часть речи слова «углерод» — Имя существительное

Морфологические признаки.

углерод (именительный падеж, единственного числа)

Постоянные признаки:

• нарицательное
• неодушевлённое
• мужской
• 2-e склонение

Непостоянные признаки:

• именительный падеж
• единственного числа

Может относится к разным членам предложения.

Склонение слова «Углерод»

Падеж	Единственное число	Множественное число
Именительный Кто? Что?	углеро́д	углеро́ды
Родительный Кого? Чего?	углеро́да	углеро́дов
Дательный Кому? Чему?	углеро́ду	углеро́дам
Винительный (неод.) Кого? Что?	углеро́д	углеро́ды
Творительный Кем? Чем?	углеро́дом	углеро́дами
Предложный О ком? О чём?	углеро́де	углеро́дах

Разбор по составу слова «Углерод»

Каким бывает «углерод»;

Синонимы к слову «углерод»

Ассоциации к слову «углерод»

Предложения со словом «углерод»

• Он знал, разумеется, что молекула двуокиси углерода поглощает энергию в инфракрасном диапазоне и что человечество выпускает эти молекулы в атмосферу в нарастающих количествах.

  Иэн Макьюэн, Солнечная

• От сгорания дизельного топлива в атмосферу поступают с выхлопными газами окись углерода, сера, мышьяк, свинец и другие токсические и канцерогенные вещества.

  Виктор Алексеев, Основы безопасности жизнедеятельности

• Количество лёгких ионов уменьшается с ухудшением микроклиматических условий в помещениях и с повышением содержания диоксида углерода.

  Владимир Николаевич Шилов, Гигиена. Конспект лекций, 2009

Происхождение слова «Углерод»

Из угле- (от уголь) + -род (от родить); первая часть — из праслав. *ǫglь, от кот. в числе прочего произошли:др.-русск. ѹгль, ѹгъль, ст.-слав. ѫгль (др.-греч. ἄνθραξ), болг. въ́гле, ср. р. «уголь», сербохорв. у̏гаљ (род. п. у̏гља), словенск. vọ̑gǝl (род. п. vọ̑gla), чешск. uhel, словацк. uhol, польск. węgiel, в.-луж. wuhl, wuhel, н.-луж. hugel; из праиндоевр. *egni- «огонь»; вторая часть — из праслав. *rodìti, от кот. в числе прочего произошли: др.-русск. родити, рожꙋ, ст.-слав. родити, рождѫ (др.-греч. γεννᾶν, τίκτειν), итер. раждати, русск. родить, рождать (церк.-слав. происхождения), укр. роди́ти, болг. родя́, сербохорв. ро̀дити, словенск. rodíti , чешск. rodit, словацк. rоdiť, польск. rodzić, в.-луж. rodźić, н.-луж. roźiś. Термин углерод, образованный по аналогии с водород, кислород как частичная калька лат. carbo, был введен в обиход Михаилом Соловьёвым в 1824 году.

Общие правила

§ 76. Пишутся слитно:

1. Все сложносокращённые слова, например: колхоз, эсминец, профсоюз, автотракторный.

2. Слова с приставками (включая вне-, после-, сверх-, а-, анти-, архи-, инфра-, контр-, ультра- и др.), а также с начальными составными частями пан-, квази-, псевдо- и др., например: довоенный, внеплановый, подотдел, аморальный, сверхприбыль, архинелепый, инфракрасный, контрудар, ультрафиолетовый, междуведомственный, панамериканизм, квазиученый, псевдоклассический.

Если приставка присоединяется к имени собственному, она пишется через дефис, например: Анти-Дюринг.

О написании с дефисом обер-, унтер-, лейб-, штаб-, вице-, экс- см. § 79, п. 13.

3. Сложные существительные, прилагательные и наречия, первым элементом которых является числительное, написанное буквами, например: пятилетка, трёхтонка, полуторагодовалый, двенадцатибалльный, двухсполовинный, троекратно.

Написание слитное и через дефис сложных иноязычных слов устанавливается в словарном порядке.

О написании через дефис собственных имён см. § 79, п. 6.

§ 77. Пишутся через дефис:

1. Лексические образования, представляющие собой:

а) повторение того же самого слова, например: маленький-маленький, еле-еле, чуть-чуть, постояли-постояли и разошлись (значение ограниченности во времени).

б) повторение того же слова или той же основы, но с разными окончаниями или приставками, например: день-деньской, рад-радёхонек, один-одинёшенек, давным-давно, черным-черно, мало-мальски, мало-помалу, крепко-накрепко, крест-накрест, толстый-претолстый, как-никак, волей-неволей, также один-единственный.

в) сочетание двух синонимических слов, например: нежданно-негаданно, тихо-смирно.

О постановке запятой (а не дефиса) при повторении слова см. § 149.

Примечание. Два одинаковых существительных в усилительном сочетании, из которых одно стоит в им. пад., а другое в твор. пад., пишутся раздельно, например: чудак чудаком, честь честью и т.п.

2. Графические буквенные сокращения сложных прилагательных, пишущихся слитно, для отличия от сокращённо написанных словосочетаний из прилагательного и существительного, например: ж.-д. – железнодорожный, но: ж. д. – железная дорога, с.-х. – сельскохозяйственный, но: с. х. – сельское хозяйство.

Дефис сохраняется в графических буквенных сокращениях слов, пишущихся через дефис, например: с.-д. – социал-демократ и социал-демократический, Ж.-Ж. Руссо – Жан-Жак Руссо.

3. Сложные слова, первым элементом которых является числительное (см. § 76, п. 3), если это числительное написано цифрами, например: 25-процентный, 10-летний, 35-летие.

4. Сложные порядковые числительные, если первая часть их написана цифрами, например: 183-миллионный, 5 1/2-тысячный.

5. Порядковые числительные, если они написаны цифрами с грамматическим окончанием, например: 15-й, 127-го.

6. Специальные термины и наименования, в том числе и аббревиатуры, в состав которых входит отдельная буква алфавита, например β-лучи (бета-лучи), или числительное, написанное цифрами и стоящее на втором месте, например ТУ-104, но: 4000 М (автопогрузчик с ковшом).

Имена существительные

§ 78. Пишутся слитно:

1. Сложные имена существительные, образованные при помощи соединительных гласных, а также все образования с аэро-, авиа-, авто-, мото-, вело-, кино-, фото-, стерео-, метео-, электро-, гидро-, агро-, зоо-, био-, микро-, макро-, нео-, например: водопровод, земледелец, льнозаготовки, паровозоремонт, аэропорт, авиаматка, автопробег, мотогонки, велодром, кинорежиссёр, фоторепортаж, стереотруба, метеосводка, электродвигатель, гидросооружения, агротехника, зоотехник, биостанция, микроснижение, макромир, неоламаркизм, веломотогонки, аэрофотосъёмка.

О написании через дефис имен существительных, образованных при помощи соединительных гласных, см. § 79, п. 3, 4.

2. Названия городов, второй составной частью которых является -град или -город, например, Ленинград, Калининград, Белгород, Ужгород, Ивангород.

3. Склоняемые сложные имена существительные с глагольной первой частью на -и, например: горицвет, держидерево, держиморда, вертишейка, вертихвостка, скопидом, сорвиголова.

§ 79. Пишутся через дефис:

1. Сложные существительные, имеющие значение одного слова и состоящие из двух самостоятельно употребляющихся существительных, соединённых без помощи соединительных гласных о и е, например:

а) жар-птица, бой-баба, дизель-мотор, кафе-ресторан, премьер-министр, генерал-майор, Бурят-Монголия (при склонении изменяется только второе существительное);

б) изба-читальня, купля-продажа, паинька-мальчик, пила-рыба, Москва-река (при склонении изменяются оба существительных).

2. Составные названия политических партий и направлений, а также их сторонников, например: социал-демократия, анархо-синдикализм, социал-демократ, анархо-синдикалист.

3. Сложные единицы измерения, независимо от того, образованы ли они при помощи соединительных гласных или без них, например: человеко-день, тонна-километр, киловатт-час. Слово трудодень пишется слитно.

4. Названия промежуточных стран света, русские и иноязычные, например: северо-восток и т.п., норд-ост и т.п.

5. Сочетания слов, имеющие значение существительных, если в состав таких сочетаний входят: а) глагол в личной форме, например: не-тронь-меня (растение), любишь-не-любишь (цветок); б) союз, например: иван-да-марья (растение); в) предлог, например: Ростов-на-Дону, Комсомольск-на-Амуре, Франкфурт-на-Майне.

6. Составные фамилии, образованные от двух личных наименований, например: Римский-Корсаков, Скворцов-Степанов, Мамин-Сибиряк, Мендельсон-Бартольди, Андерсен-Нексе.

7. Иноязычные составные фамилии с первой частью Сен- и Сент-, например: Сен-Симон, Сен-Жюст, Сен-Санс, Сент-Бёв. Так же пишутся восточные (тюркские, арабские и т.п.) личные наименования с начальной или конечной составной частью, обозначающей родственные отношения, социальное положение и т.д., например: Ибн-Фадлан, Кёр-оглы, Турсун-заде, Измаил-бей, Осман-паша.

Примечание 1. Составные имена с первой частью дон- пишутся через дефис только в тех случаях, когда вторая, основная часть имени в русском литературном языке отдельно не употребляется, например: Дон-Жуан, Дон-Кихот. Но если слово дон употребляется в значении «господин», оно пишется раздельно, например: дон Педро, дон Базилио.

Примечание 2. Артикли и частицы, входящие в состав иноязычных фамилий, пишутся отдельно, без дефиса, например: фон Бисмарк, ле Шапелье, де Костер, де Валера, Леонардо да Винчи, Лопе де Вега, Бодуэн де Куртене, фон дер Гольц. Артикли и частицы, без которых фамилии данного типа не употребляются, пишутся через дефис, например: Ван-Дейк.

В русской передаче некоторых иноязычных фамилий артикли и частицы пишутся слитно, хотя в соответствующих языках они пишутся отдельно, например: Лафонтен, Лагарп, Декандоль, Делиль.

Примечание 3. Не соединяются между собой дефисами имена разных категорий, например римские Гай Юлий Цезарь, подобно соответствующим русским имени, отчеству и фамилии.

Примечание 4. Личные имена и фамилии, соединённые с прозвищами, пишутся с последними раздельно, например: Илья Муромец, Всеволод Третий Большое Гнездо, Ванька Каин, Муравьёв Вешатель.

8. Географические названия, состоящие:

а) из двух существительных, например: Орехово-Зуево, Каменец-Подольск, Сердце-Камень (мыс);

б) из существительного и последующего прилагательного, например: Могилёв-Подольский, Гусь-Хрустальный, Москва-Товарная;

в) из сочетания артикля или частицы с знаменательной частью речи, например: Ле-Крезо (город), Ла-Каролина (город), Де-Кастри (залив).

Примечание. Раздельно пишутся географические названия:

а) состоящие из прилагательного и следующего за ним существительного или из числительного и следующего за ним существительного, например: Белая Церковь, Нижний Тагил, Великие Луки, Ясная Поляна, Семь Братьев;

б) представляющие собой сочетания имени и фамилии, имени и отчества, например: поселок Лев Толстой, станция Ерофей Павлович.

9. Названия населённых пунктов, в состав которых в качестве первой части входят: усть-, соль-, верх- и т.п., а также некоторые названия населенных пунктов с первой частью ново-, старо-, верхне-, нижне- и т.п., кроме тех, слитное написание которых закрепилось в справочных изданиях, на географических картах и т.п., например: Усть-Абакан, Соль-Илецк, Верх-Ирмень, Ново-Вязники, Нижне-Гнилое, но: Новосибирск, Малоархангельск, Старобельск, Новоалексеевка, Верхнеколымск, Нижнедевицк.

10. Составные географические названия, образованные как при помощи соединительной гласной, так и без неё из названий частей данного географического объекта, например: Австро-Венгрия, Эльзас-Лотарингия, но: Чехословакия.

11. Иноязычные словосочетания, являющиеся именами собственными, названиями неодушевлённых предметов, например: Аму-Дарья, Алма-Ата, Па-де-Кале, Булонь-сюр-Мер, Нью-Йорк, Пале-Рояль, Гранд-отель.

Примечание. Данное правило не распространяется на передаваемые русскими буквами составные иноязычные названия литературных произведений, газет, журналов, предприятий и т.п., которые пишутся раздельно, если выделяются в тексте кавычками, например: «Стандарт Ойл», «Коррьеро делла Рома».

12. Пол- (половина) с последующим родительным падежом существительного, если существительное начинается с гласной буквы или согласной л, например: пол-оборота, пол-яблока, пол-лимона, но: полметра, полчаса, полкомнаты; через дефис пишутся также сочетания пол- с последующим именем собственным, например: пол-Москвы, пол-Европы. Слова, начинающиеся с полу-, всегда пишутся слитно, например: в полуверсте от города, полустанок, полукруг.

13. Слова, первой составной частью которых являются иноязычные элементы обер-, унтер-, лейб-, штаб-, вице-, экс-, например: обер-мастер, унтер-офицер, лейб-медик, штаб-квартира, вице-президент, экс-чемпион.

Также пишется через дефис контр-адмирал (здесь контр- имеет не то значение, при котором оно пишется слитно).

14. Определяемое слово со следующим непосредственно за ним однословным приложением, например: мать-старуха, Маша-резвушка, Аника-воин.

Примечание 1. Между определяемым словом и стоящим перед ним однословным приложением, которое может быть приравнено по значению к прилагательному, дефис не пишется, например: красавец сынишка.

Примечание 2. Если определяемое слово или приложение само пишется через дефис, то между ними дефис не пишется, например: социал-демократы меньшевики.

Примечание 3. Дефис не пишется также:

а) в сочетании имени нарицательного со следующим за ним именем собственным, например: город Москва, река Волга, резвушка Маша;

б) в сочетании существительных, из которых первое обозначает родовое, а второе видовое понятие, например: птица зяблик, цветок магнолия;

в) после слов гражданин, товарищ, господин и т.п. в сочетании с существительным, например: гражданин судья, товарищ полковник, господин посол. О выделении приложения запятыми см. § 152.

15. Графические сокращения имён существительных, состоящие из начала и конца слова, например: о-во (общество), д-р (доктор), т-во (товарищество), б-ка (библиотека).

16. Дефис пишется после первой части сложного существительного при сочетании двух сложных существительных с одинаковой второй частью, если в первом из существительных эта общая часть опущена, например: шарико- и роликоподшипники (вместо шарикоподшипники и роликоподшипники), паро-, электро- и тепловозы (вместо паровозы, электровозы и тепловозы), парт- и профорганизации, северо- и юго-восток.

Имена прилагательные

§ 80. Пишутся слитно сложные имена прилагательные:

1. Образованные от слитно пишущихся сложных имён существительных, например: водопроводный (водопровод), земледельческий (земледелец, земледелие), новосибирский (Новосибирск).

2. Образованные из сочетаний слов, по своему значению подчинённых одно другому, например: железнодорожный (железная дорога), народнохозяйственный (народное хозяйство), естественнонаучный (естественные науки), сложноподчинённое (сложное по способу подчинения), рельсопрокатный (прокатывающий рельсы), общенародный (общий для народа), полезащитный (образующий защиту для полей), металлорежущий (режущий металл); сюда же относятся обозначающие единое понятие образования (в том числе и терминологические) из наречия и прилагательного (или причастия), например: малоупотребительный, близлежащий, животрепещущий, глубокоуважаемый, свежеиспеченный, ясновидящий, сильнодействующий, дикорастущий, вечнозелёный, гладкокрашеный.

Примечание. Сложные прилагательные, в состав которых входят наречия, не следует смешивать со словосочетаниями, состоящими из наречия и прилагательного (или причастия) и пишущимися раздельно, например: диаметрально противоположный, прямо противоположный, чисто русский, детски наивный, плохо скрываемый, отчётливо выраженный.

3. Употребляемые в качестве терминов и образованные из двух или трёх основ, независимо от характера последних, например: грудобрюшная (преграда), индоевропейские (языки), древневерхненемецкий (язык), двууглекислый (газ); также – глухонемой.

§ 81. Пишутся через дефис сложные имена прилагательные:

1. Образованные от существительных, пишущихся через дефис, от личных наименований – сочетаний имён и фамилий, а также от названий населённых пунктов, представляющих собой сочетания имён и фамилий, имён и отчеств, например:

дизель-моторный, социал-демократический, бурят-монгольский, северо-восточный, алма-атинский, орехово-зуевский, нижне-масловский, усть-абаканский, ромен-роллановский, вальтер-скоттовский, лев-толстовский, ерофей-павловичский.

Примечание 1. Пишется слитно прилагательное москворецкий.

Примечание 2. Имена прилагательные, образованные от имён собственных, пишущихся через дефис, и имеющие приставку, отсутствующую у существительного, пишутся слитно, например: приамударьинский, заиссыккульский.

2. Образованные из двух или более основ, обозначающих равноправные понятия, например: беспроцентно-выигрышный, выпукло-вогнутый, партийно-комсомольский, садово-огородный, мясо-молочный, англо-японский, русско-немецко-французский (словарь), сине-бело-красный (флаг).

3. Образованные из двух основ и обозначающие:

а) качество с дополнительным оттенком, например: раскатисто-громкий, горько-солёный;

б) оттенки цветов, например: бледно-розовый, ярко-синий, тёмно-русый, чёрно-бурый, синевато-голубой, золотисто-жёлтый, пепельно-серый, бутылочно-зелёный, лимонно-жёлтый, изжелта-красный.

4. Входящие в состав географических собственных имён и начинающиеся с восточно-, западно-, северно- и северо-, южно- и юго-, например: Западно-Казахстанская область, Восточно-Китайское море, Южно-Африканский Союз.

Примечание 1. Прилагательные, образованные из двух или более основ, не подходящие под перечисленные правила, пишутся через дефис, например:

литературно-художественный (альманах), политико-массовая (работа), словарно-технический (отдел), подзолисто-болотный, рыхло-комховато-пылеватый, удлинённо-ланцетовидный.

Примечание 2. Через дефис пишутся также слова, первой составной частью которых являются сам-, сама-, например: сам-друг, сам-третей, сам-пят, сама-пята.

Имена числительные

§ 82. Пишутся слитно во всех падежах:

1. Количественные числительные, последним элементом которых является -десят, -ста, -сот, например: пятьдесят, пятидесяти, триста, трёхсот, семьсот, семисот, но: пять тысяч, три миллиона, семь миллиардов.

2. Порядковые числительные, последним элементом которых является -сотый, -тысячный, -миллионный и т.д., если первая часть их написана буквами, например: восьмисотый, двадцатипятитысячный, стовосьмидесятитрёхмиллионный, но: восемьдесят шестой, тысяча девятьсот сорок первый.

Примечание. В сложных порядковых числительных, в состав которых входят дробные обозначения «с половиной», «с четвертью» и т.п., предпочтительно писать первую составную часть цифрами, например: 5 1/2-тысячное население.

Наречия

§ 83. Пишутся слитно:

1. Наречия, образованные соединением предлогов с наречиями, например: доныне, извне, навсегда, напротив, насквозь, позавчера, послезавтра, донельзя, навряд ли, задаром.

От таких наречий следует отличать пишущиеся раздельно сочетания предлогов с неизменяемыми словами, употребляемыми в этих случаях в значении существительных, например: до завтра, на авось, на нет (свести на нет), на ура.

2. Наречия, образованные соединением предлогов в и на с собирательными числительными, например: вдвое, втрое, вчетверо и т.д., надвое, натрое, но: по двое, по трое.

3. Наречия, образованные соединением предлогов с краткими прилагательными, например: влево, досуха, замертво, издалека, наскоро, понемногу, попусту, потихоньку, сгоряча.

4. Наречия, образованные соединением предлогов с полными прилагательными и местоимениями, например: вкрутую, вплотную, врукопашную, зачастую, напропалую, наудалую, впервые, наверное, вничью, вовсю.

Примечание. Пишутся раздельно наречия этого типа, составленные из предлога в и прилагательного, начинающегося с гласной, например: в открытую.

О наречиях, начинающихся с по- и пишущихся через дефис, см. § 84.

5. Наречия, образованные соединением предлогов с существительными, например: вперёд, сбоку, подчас, воочию, встарь, взапуски, наугад, вдобавок, наоборот, поневоле, всмятку, вприсядку. К наречиям этого типа принадлежат:

а) Слова с различными наречными значениями, имеющие в своём составе такие существительные или такие именные формы, которые в современном литературном языке не употребляются: вблизи, вдоволь, вдогонку, вдребезги, взаймы, взамен, взаперти, взапуски, взасос, взашей, вкось, вкривь, внаймы, внутри, внутрь, воочию, восвояси, вперевалку, вперегонки, впереди, вперемежку, вперемешку, вплавь, вповалку, впопыхах, вприглядку, впроголодь, впросак, впросонках, вразвалку, врасплох, врозь, всерьез, вскачь, вскользь, всмятку, встарь, втихомолку, второпях, втридорога, вчуже, дотла, замуж (от старой формы вин. пад.), запанибрата, изнутри, искони, исподволь, исподлобья, исподтишка, испокон, исполу, исстари, набекрень, наверняка, навзничь, навзрыд, навыворот, назади, наземь, наизусть, наискосок, наискось, наобум, наотмашь, наперегонки, наперекор, наперерез, наперечёт, наповал, напрямик, нарасхват, наружу, насмарку, настежь, настороже, натощак, наугад, наутёк, начеку, наяву, невдомёк, невзначай, невмоготу, невпопад, оземь, поделом, позади, понаслышке, поодаль, поперёк, пополам, пополудни, сдуру, сзади, снаружи, спозаранку, спросонок, спросонья, чересчур и т.п.

б) Слова с различными наречными значениями, если между предлогом (приставкой) и существительным, из которых образовалось наречие, не может быть без изменения смысла вставлено определяющее прилагательное, местоимение, числительное или если к существительному не может быть поставлен падежный вопрос:

вдобавок, вброд, влёт, вволю, вволюшку (наесться), взатяжку (курить), вконец (измучиться), вместе, вмиг, внакидку (носить пальто), внакладе, вновь, воистину, вокруг, вослед, вперебой, вперегиб, вплоть, впору (костюм), вовремя (приехать), впоследствии, вполовину, вправду, вправе (поступить так), впрок, вразбивку, вразброд, вразнобой, вразрез, вразрядку, врастяжку, вряд ли, вскорости, вслух, всухомятку, втайне, въявь, задаром, замужем, зараз, кряду, кстати, набок (надеть шляпу), навстречу, навыкат, навылет, навынос, навыпуск, навырез, навытяжку, наголову (разбить), назло, назубок (выучить), наизнанку, накануне, наконец, налицо, наоборот, наотрез, наперебой, наперевес, наполовину, наперерыв, наперехват, напоказ, напоследок, например, напрокат, напролёт, напролом, нараспашку, нараспев, наряду, насилу, насмерть (стоять; но: не на жизнь, а на смерть), наудачу, наутро (вернуться), начистоту, невмочь, обок (жить), отроду, отчасти, побоку, подряд, подчас, поневоле, поодиночке, поутру, сбоку, слишком, сплеча (рубить), сразу, сроду, сряду.

в) Слова с пространственным и временным значением, имеющие в своём составе существительные верх, низ, перед, зад, высь, даль, век, начало, несмотря на возможность постановки перед некоторыми из них определяющего слова: вверх, вверху, кверху, доверху, наверх, сверху; вниз, внизу, книзу, донизу, снизу; вперёд, наперёд; назад; ввысь; вдаль, вдали, издали; ввек, вовек, вовеки, навек, навеки; вначале, сначала; но при наличии пояснительных слов к соответствующим существительным указанные слова пишутся раздельно, например: на верх горы, в высь поднебесную, в даль степей, в дали голубой, во веки веков, на веки вечные, в начале жизни, с начала учебного года.

6. Однако не всякое сочетание существительного с предлогом, являющееся обстоятельством и близкое по значению к наречию, пишется слитно.

А. Следует писать раздельно сочетания предлогов с существительными:

а) если между предлогом и существительным можно вставить определяющее слово: на миг (на один миг), с маху (со всего маху), в тиши (в лесной тиши), на скаку (на всём скаку), в тупик (попал в такой тупик, что…);

б) если предлог оканчивается на согласную, а существительное начинается с гласной буквы: в обмен, в обрез, в обнимку, в отместку, в обтяжку, в обхват, в одиночку, в охапку, в упор, под уклон;

в) если существительное в определённом (одном) значении сохранило хотя бы некоторые падежные формы в сочетании с предлогами: на корточки, на корточках; на карачки, на карачках; на четвереньки, на четвереньках; за границу, за границей, из-за границы; под спуд, под спудом; на дом, на дому; на память, по памяти; на совесть, по совести; на руку, не с руки; в насмешку, с насмешкой; под мышками, под мышки, под мышкой, под мышку, из-под мышек; на цыпочки, на цыпочках; на поруки, на поруках; на запятки, на запятках.

Б. Раздельно пишутся также:

а) некоторые близкие по значению к наречиям сочетания существительных с предлогами:

без: без оглядки, без просыпу, без разбору, без толку, без удержу, без умолку, без устали;

до: до зарезу, до отвала, до отказа, до смерти, до упаду (но: доверху, донизу, см. выше п. 5, «в»);

на: на бегу, на лету, на ходу, на весу, на виду, на вид, на вес, на вкус, на глаз, на глазок, на грех, на диво, на ощупь, на славу, на смех;

с: с налёту, с разбегу, с разгона, с размаху, с наскока, с ходу;

б) сочетания отрицаний не и ни с предложными формами существительных, например: не в меру, не в зачёт, не под силу, не по вкусу, не к добру, ни на йоту, ни за грош, не к спеху,

в) существительные в предложном падеже множественного числа с предлогами в и на, обозначающие местонахождение, время, состояние (физическое и душевное), например: в головах, в ногах, на часах (стоять), на днях, на рысях, на радостях, в сердцах.

В случаях затруднений в правописании наречий, образованных соединением предлога с именами существительными, следует обращаться к орфографическому словарю.

От слитно пишущихся наречий следует отличать одинаково произносимые сочетания предлогов с существительными, пишущиеся раздельно, например: в пору юности, с боку на бок (переваливается), на голову (свалилось несчастье), на силу (не рассчитывали), на пример (сослался), в ряд (выстроились).

7. Пишутся слитно наречия, образовавшиеся путем слияния предлогов с местоимениями, например: почему, потому, поэтому, посему, отчего, оттого, зачем, затем, почём («по какой цене») и т.п., в отличие от сочетаний предлогов с местоимениями в косвенных падежах («по чему ты стучишь?», т.е. по какому предмету; «за чем ты пошёл?», т.е. за какой вещью ты пошёл).

§ 84. Пишутся через дефис наречия во-первых, во-вторых, в-третьих и т.д., а также наречия, образованные от прилагательных и местоимений, начинающиеся с по- и оканчивающиеся на -ки, -ьи, -ому, -ему, например: по-русски, по-немецки (а также по-латыни), по-птичьи, по-соловьиному, по-иному, по-моему, по-пустому, по-прежнему, по-видимому.

Примечание. Наречия, образованные из предлога по и краткой формы прилагательного, пишутся (согласно § 83, п. 3) слитно.

В наречиях с приставкой по-, образованных от составных имён прилагательных, пишущихся с дефисом, дефис пишется только после по-, например: по-социалдемократически.

Примечание. Пишется через дефис наречие на-гора (технический термин).

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Всего найдено: 7

Здравствуйте! Подскажите, как пишется «углеродно(-)нейтральный? Спасибо!

Ответ справочной службы русского языка

Корректно раздельное написание.

Здравствуйте! Скажите, пожалуйста, правильно ли расставлены знаки препинания в предложении. При вдохе оксида углерода кровь альвеолярных капилляров, вместо того чтобы обогащаться кислородом, обогащается угарным газом.

Ответ справочной службы русского языка

Знаки препинания расставлены верно.

Можно ли уже, на ваш взгляд, использовать в текстах (журнальных и т. п.) слово «карбон» в значении «углепластик»? Употребляется оно широко и звучит красиво :), но есть сомнения, поскольку имеется значение «каменноугольный период», а в исходном английском carbon – это просто «углерод«. Спасибо!

Ответ справочной службы русского языка

Если читателям журнала понятно, о чем идет речь, то почему бы и нет.

Здравствуйте! Правильно ли писать слитно слово «невиноградного» в словосочетании «углерод невиноградного происхождения»?

Ответ справочной службы русского языка

Слитное написание правильно.

Здравствуйте, не могли бы мне помочь, хотелось бы узнать есть ли в этом предложении запятая после слова свойств. Предложение целиком: Для обеспечения высоких прочностных свойств, роторы крупных турбогенераторов (свыше 500 МВт) изготавливают из цельной поковки высоколегированной стали, обладающей высокими механическими и магнитными свойствами, а роторы турбогенераторов малой мощности (до 100 МВт) — из углеродистой стали

Ответ справочной службы русского языка

Запятая после слова свойств не нужна.

Здравствуйте. Нужна ли запятая после «однако» в данном предложении: однако, исходя из теоретической возможности заполнения атомами углерода междоузлий подрешетки, более верно считать ее модификацией карбида?

Ответ справочной службы русского языка

Знаки препинания расставлены верно.

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баллиститные и смесевые твердые ракетные топлива и заряды из них для всех родов войск и вооружений, ракет-носителей и космических объектов.

Здесь создана непрерывная технология производства баллиститных порохов и твердых ракетных топлив, а также зарядов различных форм и габаритов с широким спектром управляемых свойств.
Разработана и внедрена безопасная промышленная технология производства смесевых твердых ракетных топлив с высоким уровнем энергомассовых характеристик и экологической частотой продуктов сгорания.

Федеральный центр является автором и разработчиком технологии изготовления корпусов твердотопливных ракетных двигателей из современных композиционных материалов, в том числе сверхпрочных цельномотанных корпусов типа «кокон».

За годы работы предприятием сдано в эксплуатацию более 460 номенклатур твердотопливных зарядов различного назначения.

Так для сухопутных войск страны отработаны заряды к 59 ракетным комплексам, в том числе к активно-реактивным снарядам «Ель-2», «Буревестник-2», «Баклан», «Краснополь».
К артиллерийским установкам и комплексам «Б-4М», «Пион», «Гиацинт», «2СЗМ», «Смельчак».
К реактивным системам залпового огня «Град», «Град-1», «Ураган».
Для войск ПВО страны отработаны заряды к 10 ракетным комплексам, среди них комплексы: «С-200», «Печора», «Куб», «Шторм»,
«Волга», «Тунгуска».
Военно-морскому флоту России сданы на вооружение заряды к 35 ракетным системам.
Для военно-воздушных сил страны отработаны заряды к 30 боевым ракетам.
В ракетных комплексам тактического и стратегического назначения «Темп-С», «Ока» и «Ока-У», «Точка» и «Точка-У», «Пионер», «Тополь», также используются заряды отработанные «Салютом».

Убедительным признанием его заслуг, в общем, для всех деле укреплении безопасности нашей страны, стало открытие монумента «Создателям ядерного щита России».

Федеральный центр «Салют» – один из ведущих научных центров страны по проблемам долговечности твердотопливных зарядов. По результатам проведенных здесь комплексных исследований продлены сроки эксплуатации зарядов к более чем 50 ракетным комплексам, стоящим на вооружении в России, Емени, Сирии, на Кубе, Замбии, Перу и ряде других стран.
Снятые с вооружения пороха и твердые ракетные топлива, после их утилизации эффективно используются для решения народно-хозяйственных задач, например: в качестве детонирующих зарядов сейсморазведки и для рыхления твердых горных пород, в качестве безкорпусного генератора давления в скважинах с целью изучения притока к ним нефти и газа.

С помощью гранипоров – гранулированных взрывчатых веществ на основе баллиститов, ведется разработка полезных ископаемых открытым способом.

Федеральный центр является неизменным участником практически всех космических программ, осуществляемых в России. По этим программам отработаны заряды и двигатели к 24 космическим комплексам. Это система аварийного спасения космонавтов, двигатели мягкой посадки, стабилизации, увода, разделения ступеней, торможения космических объектов для комплексов «Восток», «Восход», «Луна», «Марс», «Союз-ТМ», «Протон», «Морской старт», «Циклон», «Молния» и других.

В начале 90-х годов Федеральных центр приступил к разработке технологий двойного назначения и выпуска на их основе наукоемкой гражданской продукции. Так на базе оборонных технологий были созданы уникальные источники электрической энергии – импульсные МГД-генераторы. Они предназначены для глубинного зондирования земной коры и поиска полезных ископаемых.

Разработаны специальные, аэрозольобразующие составы с ингибирующими добавками для принципиально новых средств объемного пожаротушения. Это огнетушители «Степ» и «Степ2», которые эффективно заменяют хладоновые средства борьбы с огнём.
«Степ» и «Степ2» — надежная защита от пожара электростанций, производственных и складских помещений, всех видов транспорта, объектов добычи и переработки нефти и газа и ряда других объектов.
«Степ» и «Степ2» успешно прошли испытания в России и за рубежом. Сегодня они экспортируются во многие страны мира.

На основе использование твердотопливных газогенераторов и емкостей из композиционных материалов, созданы быстродействующие установки жидкостного тушения крупных пожаров. Создана опытно- промышленная установка для синтеза алмазов из специальных углеродосодержащих твердотопливных составов.
Основные области применениям таких алмазов шлифовально- полировальные пасты и алмазно-абразивные инструменты.
На базе технологии производства корпусов ракетных двигателей освоен выпуск различных емкостей: контейнеров, труб и другого химически стойкого оборудования. Разработана технология, налажен выпуск оборудования и материалов для керамической сварки, огнеупорных покрытий высокотемпературных печей.
На основе самораспространяющегося высокотемпературного синтеза, разработана технология переработки металлосодержащих отходов в стойкие неорганические пигменты различных цветов и оттенков.

Сегодня Федеральный центр является одним из крупнейших в России изготовителем субстанций для производства сердечно-сосудистых препаратов.

Среди других видов гражданской продукции «Салюта», следует отметить бездымные фейерверочные составы, полимерные магниты, технику и материалы для разметки дорог, лаки и краски.

«Салют» – один из участников проекта «СТАРТ 1». Его основу составляет носитель, созданный на базе многоступенчатой твердотопливной ракеты мобильного грунтового стратегического комплекса.

«СТАРТ 1» предназначен для вывода на околоземные орбиты космических аппаратов с целью развертывания систем спутниковой связи, создании новых материалов, разведки полезных ископаемых, экологического мониторинга и других целей.

Федеральный центр «Салют» приглашает все заинтересованные организации к сотрудничеству в области разработки производства и сбыта своей продукции.

Ответ справочной службы русского языка

К сожалению, мы не имеем возможности ответить на столь объёмный вопрос.

Оксид углерода (II) 
 1. Строение молекулы и физические свойства 
 2. Способы получения 
3. Химические свойства
3.1. Взаимодействие с кислородом
3.2. Взаимодействие с хлором
3.3. Взаимодействие с водородом
3.4. Взаимодействие с щелочами
3.5. Взаимодействие с оксидами металлов
3.6. Взаимодействие с прочими окислителями

Оксид углерода (II)

Строение молекулы и физические свойства

Оксид углерода (II) («угарный газ») –  это газ без цвета и запаха. Сильный яд. Небольшая концентрация угарного газа в воздухе может вызвать сонливость и головокружение. Большие концентрации угарного газа вызывают удушье.

Строение молекулы оксида углерода (II) – линейное. Между атомами углерода и кислорода образуется тройная связь, за счет дополнительной донорно-акцепторной связи:

Способы получения

В лаборатории угарный газ  можно получить действием концентрированной серной кислоты на муравьиную или щавелевую кислоты:

НСООН  →   CO   +  H₂O

H₂C₂O₄ → CO + CO₂ + H₂O

В промышленности угарный газ получают в газогенераторах при пропускании воздуха через раскаленный уголь:

C + O₂ → CO₂

CO₂ + C → 2CO

Еще один важный промышленный способ получения угарного газа — паровая конверсия метана. При взаимодействии перегретого водяного пара с метаном образуется угарный газ и водород:

СН₄ + Н₂O → СО + 3Н₂

Также возможна паровая конверсия угля:

C⁰ + H₂⁺O → C⁺²O + H₂⁰

Угарный газ в промышленности также можно получать неполным окислением метана:

2СН₄+О₂ → 2СО + 4Н₂

Химические свойства

Оксид углерода (II) –  несолеобразующий оксид. За счет углерода со степенью окисления +2 проявляет восстановительные свойства.

1. Угарный газ горит в атмосфере кислорода. Пламя окрашено в синий цвет:

2СO +  O₂ → 2CO₂

2. Оксид углерода (II) окисляется хлором в присутствии катализатора или под действием света с образованием фосгена. Фосген – ядовитый газ.

CO   +   Cl₂ → COCl₂

3. Угарный газ взаимодействует с водородом при повышенном давлении. Смесь угарного газа и водорода называется синтез-газ. В зависимости от условий из синтез-газа можно получить метанол, метан, или другие углеводороды.

Например, под давлением больше 20 атмосфер, при температуре 350°C и под действием катализатора угарный газ реагирует с водородом с образованием метанола:

СО + 2Н₂ → СН₃ОН

4. Под давлением оксид углерода (II) реагирует с щелочами. При этом образуется формиат – соль муравьиной кислоты.

Например, угарный газ реагирует с гидроксидом натрия с образованием формиата натрия:

CO + NaOH → HCOONa

5. Оксид углерода (II) восстанавливает металлы из оксидов.

Например, оксид углерода (II) реагирует с оксидом железа (III) с образованием железа и углекислого газа:

3CO   +   Fe₂O₃   →  2Fe   +   3CO₂

Оксиды меди (II) и никеля (II)  также восстанавливаются угарным газом:

СО     +   CuO   →    Cu    +   CO₂

СО     +   NiO   →   Ni    +   CO₂

6. Угарный газ окисляется и другими сильными окислителями до углекислого газа или карбонатов.

Например, пероксидом натрия:

CO   +   Na₂O₂ → Na₂CO₃