CARBON DIOXIDE

Carbon dioxide is a chemical compound with the chemical formula CO2. 
Carbon dioxide is made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. 
Carbon dioxide is found in a gas state at room temperature and at normally-encountered concentrations it is odorless. 

CAS:    124-38-9
MF:    CO2
MW:    44.01
EINECS:    204-696-9

Synonyms
Carbon dioxide-free water;Standard solution for the determination of carbon dioxide;carbondioxide(non-specificname);carbondioxide,refrigeratedliquid;carbondioxide,solid;carbondioxidegas;carbondioxideliquide;carbondioxidesolid

As the source of carbon in the carbon cycle, atmospheric Carbon dioxide is the primary carbon source for life on Earth. 
In the air, carbon dioxide is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas. 
Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, and seawater.
Carbon dioxide is a trace gas in Earth's atmosphere at 428 parts per million (ppm),[a] or about 0.043% (as of July 2025) having risen from pre-industrial levels of 280 ppm or about 0.028%.
Burning fossil fuels is the main cause of these increased CO2 concentrations, which are the primary cause of climate change.
Carbon dioxide's concentration in Earth's pre-industrial atmosphere since late in the Precambrian was regulated by organisms and geological features. 
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.
In turn, oxygen is consumed and Carbon dioxide is released as waste by all aerobic organisms when they metabolize organic compounds to produce energy by respiration.
Carbon dioxide is released from organic materials when they decay or combust, such as in forest fires. 
When carbon dioxide dissolves in water, it forms carbonate and mainly bicarbonate (HCO3–), which causes ocean acidification as atmospheric Carbon dioxide levels increase.

Carbon dioxide is 53% denser than dry air, but is long-lived and thoroughly mixes in the atmosphere. 
About half of excess Carbon dioxide emissions to the atmosphere are absorbed by land and ocean carbon sinks.
These sinks can become saturated and are volatile, as decay and wildfires result in the CO2 being released back into the atmosphere.
CO2, or the carbon it holds, is eventually sequestered (stored for the long term) in rocks and organic deposits like coal, petroleum and natural gas.
Nearly all CO2 produced by humans goes into the atmosphere. 
Less than 1% of CO2 produced annually is put to commercial use, mostly in the fertilizer industry and in the oil and gas industry for enhanced oil recovery. 
Other commercial applications include food and beverage production, metal fabrication, cooling, fire suppression and stimulating plant growth in greenhouses.

Carbon dioxide (CO2) is the 18th most frequently produced chemical in the United States. 
Carbon dioxide has numerous uses, including in refrigeration, in the manufacture of carbonated drinks (e.g., soda pop), in fire extinguishers, in providing an inert atmosphere (unreactive environment), and as a moderator for some types of nuclear reactors.
Carbon dioxide is used quite extensively to refrigerate dairy products, meat products, frozen foods, and other perishable foods while in transit.
Carbon dioxide is also used as a cooling agent in many industrial processes, such as grinding heat-sensitive materials, rubber tumbling, cold-treating metals, shrink fitting of machinery parts, vacuum cold traps, and so on.
Gaseous carbon dioxide is used to carbonate soft drinks, for pH control in water treatment, in chemical processing, as a food preservative, as an inert blanket in chemical and food processing and metal welding, as a growth stimulant for plant life, for hardening molds and cores in foundries, and in pneumatic devices.
Carbon dioxide is used as an expendable refrigerant for freezing and chilling food products; for low-temperature testing of aviation, missile, and electronic components; for stimulation of oil and gas wells; for rubber tumbling; and for controlling chemical reactions.
Carbon dioxide is also used as a fire extinguishing agent in portable and built-in fire extinguishing systems.

Carbon dioxide is a colorless, odorless, noncombustible gas present throughout the atmosphere and is an essential compound for life on Earth. 
Carbon dioxide is found on other planets in the solar system. 
Mars’s icecaps are primarily frozen carbon dioxide and Venus’s atmosphere is mostly carbon dioxide. 
Carbon dioxide occurs naturally as approximately 0.03% v/v of the atmosphere.
Carbon dioxide, also known as dry ice, is usually encountered as white-colored pellets or blocks.
A one-carbon compound with formula CO2 in which the carbon is attached to each oxygen atom by a double bond. 
A colourless, odourless gas under normal conditions, Carbon dioxide is produced during respiration by all animals, fungi and microorganism that depend directly or indirectly on living or decaying plants for food.
The solution of carbon dioxide in a liquid under pressure, as in carbonated soft drinks.
The addition of carbon dioxide to compounds, e.g. the insertion of carbon dioxide into Grignard reagents.

A colourlessodourless gas, CO2, soluble in water,ethanol, and acetone; d. 1.977 g dm–3(0°C); m.p. –56.6°C; b.p. –78.5°C. 
Carbon dioxide occursin the atmosphere (0.04% by volume)but has a short residence timein this phase as it is both consumedby plants during photosynthesis andproduced by respiration and by combustion.
Carbon dioxide is readily prepared in thelaboratory by the action of diluteacids on metal carbonates or of heaton heavy-metal carbonates. 
Carbondioxide is a by-product from themanufacture of lime and from fermentationprocesses.
Carbon dioxide has a small liquidrange and liquid carbon dioxide isproduced only at high pressures. 
The molecule CO2 is linear with each oxygenmaking a double bond to the carbon.Chemically, it is unreactive andwill not support combustion. 
Carbon dioxide dissolves in water to give carbonicacid.
Large quantities of solid carbondioxide (dry ice) are used in processesrequiring large-scale refrigeration. 
Carbon dioxide is also used in fire extinguishers as adesirable alternative to water formost fires, and as a constituent ofmedical gases as it promotes exhalation.
Carbon dioxide is also used in carbonateddrinks.
The level of carbon dioxide in the atmosphere has increased by some12% in the last 100 years, mainly becauseof extensive burning of fossilfuels and the destruction of largeareas of rain forest. 
This has beenpostulated as the main cause of theaverage increase of 0.5°C in global temperatures over the same period,through the greenhouse effect.
Steps are now being taken to preventfurther increases in atmospheric CO2 concentration and subsequent globalwarming.

Carbon dioxide is a colourless and odourless gas that is a natural component of the air and part of the global carbon cycle. 
Carbon dioxide plays an important role in photosynthesis, in which plants convert CO₂ into oxygen. 
At the same time, Carbon dioxide is a significant greenhouse gas that contributes to global warming and climate change. 
Carbon dioxide's concentration is influenced by natural processes and human activities such as the burning of fossil fuels. 
Monitoring and controlling CO₂ emissions are therefore central to environmental protection and climate policy.
Carbon dioxide is a colorless, odorless gas at room temperature and pressure, known for its role in the Earth's atmosphere and biological processes. 
Carbon dioxide is a linear molecule, consisting of one carbon atom covalently bonded to two oxygen atoms, with a molecular weight of approximately 44.01 g/mol. 
Carbon dioxide is produced naturally through processes such as respiration, combustion, and decomposition, and it is also a byproduct of various industrial activities. 
Carbon dioxide is soluble in water, forming carbonic acid, which plays a crucial role in the carbon cycle and ocean chemistry. 
Carbon dioxide is a greenhouse gas, contributing to global warming by trapping heat in the atmosphere. 
Carbon dioxide's concentration is monitored due to its environmental impact, particularly in relation to climate change. 
In terms of safety, Carbon dioxide is generally non-toxic at low concentrations, but high levels can lead to asphyxiation by displacing oxygen in the air. 
Carbon dioxide's CAS number, 124-38-9, is used for identification in chemical databases and regulatory frameworks.

Carbon dioxide Chemical Properties
Melting point: −78.5 °C(lit.)
Boiling point: -78.46°C
density: 1.977（0℃）
vapor density: 1.52 (vs air)
vapor pressure: 56.5 atm ( 20 °C)
refractive index: 1.0004
storage temp.: −70°C
solubility: At 20 °C and at a pressure of 101 kPa, 1 volume dissolves in about 1 volume of water.
form: colorless gas
color: colorless
Odor: at 100.00%. odorless
Water Solubility: mL CO2/100mL H2O at 760mm: 171 (0°C), 88 (20°C), 36 (60°C) [MER06]
Thermal Conductivity: 0.016632 W/(m·K)
Merck: 13,1819
BRN: 1900390
Henry's Law Constant: 3.4×10-4 mol/(m3Pa) at 25℃, Burkholder et al. (2019)
Exposure limits    TLV-TWA 5000 ppm (～9000 mg/m3) (ACGIH, MSHA, and OSHA); STEL 30,000 ppm (ACGIH).
Dielectric constant: 1.6（0℃）
Stability: Stable. Incompatible with chemically active metals, such as alkali metals.
Cosmetics Ingredients Functions: PROPELLANT
InChI: 1S/CO2/c2-1-3
InChIKey: CURLTUGMZLYLDI-UHFFFAOYSA-N
LogP: 0.830 (est)
Surface tension: 1.19mN/m at 293.15K
CAS DataBase Reference: 124-38-9(CAS DataBase Reference)
EPA Substance Registry System: Carbon dioxide (124-38-9)
CAS Number Unlabeled: 124-38-9

Carbon dioxide,CO2, also known as carbonic anhydride and carbonic acid gas, is a colorless,odorless gas that liquifies at -65 °C(-86 OF) and solidifies in dry ice at -78.2 °C(-107 OF). 
Carbon dioxide is soluble in water,alcohol, and most alkaline solutions. 
In a relatively slow reaction,carbon dioxide hydrates in water to become carbonic acid and is corrosive. 
In petroleum production, the velocity of the carbon dioxide gas can increase the corrosion rate to very high levels,with the presence of salts becoming unimportant. 
Carbon dioxide is used in preparing carbonated beverages, fire extinguishers, dry ice refrigerants,and as a raw material in the production of sodium carbonate and sodium bicarbonate using the Solvay procedure.

Physical properties    
Colorless, odorless and tasteless gas; 1.53 times heavier than air; density 1.80 g/L at 25°C; can be liquefied under pressure; liquefies at -56.6°C at 5.2 atm; density of liquid CO2 at 0°C and 34 atm 0.914 g/mL; solidifies to white snow-like flakes known as dry ice, density 1.56 g/cm3 at -79°C; dry ice sub limes to CO2 gas at -78.5°C; critical temperature 31°C; critical pressure 72.79 atm, critical density 94 cm3/mol; moderately soluble in water, solubility 173 mL and 88mL CO2/100 mL water at 0°C and 20°C, respectively; solubility increases with pressure.

Uses    
In the carbonation of beverages; manufacture of carbonates; in fire prevention and extinction; for inerting flammable materials during manufacture, handling and transfer; as propellant in aerosols; as dry ice for refrigeration; to produce harmless smoke or fumes on stage; as rice fumigant; as antiseptic in bacteriology and in the frozen food industry. 
Supercritical or liquid CO2 used in extraction of caffeine and hops aroma; dry cleaning; metal degreasing; cleaning semiconductor chips; paint spraying; polymer modification. 
Environmentally benign alternative to potentially hazardous solvents in organic and polymer chemistry.
Carbon Dioxide is a gas obtained during fermentation of glucose (grain sugar) to ethyl alcohol. Carbon dioxide is used in pressure-packed foods as a propellant or aerating agent and is also used in the carbonation of beverages. 
Carbon dioxide is released as a result of the acid carbonate reaction of leavening agents in baked goods to produce an increase in volume. 
As a solid, Carbon dioxide is termed dry ice and is used for freezing and chilling.

Carbon dioxide has several major uses： Solid carbon dioxide, dry ice, is used as a refrigerant. 
Another major use of carbon dioxide is in the soda industry. 
Soda is sodium carbonate monohydrate (Na2CO3 H2O). 
Other forms of soda include washing soda, which is sodium carbonate decahydrate (Na2CO3 10H2O), and baking soda, which is sodium bicarbonate (NaHCO3).
Carbon dioxide is used as a gas in fire extinguishers, as an inflation gas for flotation devices, and as a propellant (for example in air guns). 
In recent years, the use of carbon dioxide as a supercritical fluid in green chemistry applications has increased. 
A supercritical fluid is a fluid with a temperature and pressure above its critical point.

Pharmaceutical Applications    
Carbon dioxide and other compressed gases such as nitrogen and nitrous oxide are used as propellants for topical pharmaceutical aerosols. 
They are also used in other aerosol products that work satisfactorily with the coarse aerosol spray that is produced with compressed gases, e.g. cosmetics, furniture polish, and window cleaners.
The advantages of compressed gases as aerosol propellants are that they are less expensive; are of low toxicity; and are practically odorless and tasteless. 
Also, in comparison to liquefied gases, their pressures change relatively little with temperature. 
However, the disadvantages of compressed gases are that there is no reservoir of propellant in the aerosol and pressure consequently decreases as the product is used. 
This results in a change in spray characteristics. 

Additionally, if a product that contains a compressed gas as a propellant is actuated in an inverted position, the vapor phase, rather than the liquid phase, is discharged. 
Most of the propellant is contained in the vapor phase and therefore some of the propellant will be lost and the spray characteristics will be altered. 
Also, sprays produced using compressed gases are very wet. Valves, such as the vapor tap or double dip tube, are currently available and will overcome these problems.
Carbon dioxide is also used to displace air from pharmaceutical products by sparging and hence to inhibit oxidation. 
As a food additive Carbon dioxide is used to carbonate beverages and to preserve foods such as bread from spoilage by mold formation, the gas being injected into the space between the product and its packaging.
Solid carbon dioxide is also widely used to refrigerate products temporarily, while liquid carbon dioxide, which can be handled at temperatures up to 318℃ under high pressure, is used as a solvent for flavors and fragrances, primarily in the perfumery and food manufacturing industries.

Foods
Carbon dioxide is a food additive used as a propellant and acidity regulator in the food industry. 
Carbon dioxide is approved for usage in the EU[121] (listed as E number E290), US, Australia and New Zealand.
A candy called Pop Rocks is pressurized with carbon dioxide gas at about 4,000 kPa (40 bar; 580 psi). 
When placed in the mouth, Carbon dioxide 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.
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.

Production Methods    
Carbon dioxide accounts for 0.037% by volume of the atmosphere.
Several methods can be used to produce large volumes of CO2. 
The combustion of coke or other carbonaceous substances produces results in CO2: C(coke) + O2 → CO2(g).
In combustion processes, CO2 is concentrated by separating it from other gases using scrubbing and absorption techniques. 
Another source of CO2 involves the calcination (slow heating) of carbonates such as limestone, CaCO3: CaCO3(s)→ CaO + CO2(g).
This process takes place in a lime kiln in the production of precipitated calcium carbonate at temperatures of from 500°C to 900°C. 
Carbon dioxide is also produced as a by-product in fermentation reactions to produce alcohols. 
An example is the fermentation of glucose, C6H12O6 to ethanol (C2H5OH): C6H12O6(aq)→ 2C2H5OH(aq) + 2CO2(g). 
Carbon dioxide is produced as a by-product in a number of syntheses, such as the Haber process, to produce ammonia.

Preparation    
Carbon dioxide is produced as a by-product in many processes. 
Carbon dioxide is pro duced as a by-product in the manufacture of lime from calcium carbonate:

CaCO3 →CaO + CO2
CO2 also is derived from synthesis gas which is a mixture of CO, CO2, H2 and N2 from air obtained by steam reforming. 
Carbon dioxide also is obtained by combustion of natural gas:
CH4 + 2O2 → CO2 + 2H2O
Carbon dioxide also is obtained as a by-product in the Haber-Bosch process for the man ufacture of ammonia. 
The method involves passing steam and air over hot coke.
Carbon dioxide also is produced along with ethanol from fermentation of carbohydrates by yeast:
C6H12O6→2CO2 + 2C2H5OH
In the laboratory, CO2 may be produced by the reaction of any carbonate with a dilute mineral acid:
CaCO3 + 2HCl → CaCl2 + CO2 + H2O

Production Methods    
Carbon dioxide is obtained industrially in large quantities as a byproduct in the manufacture of lime; by the incineration of coke or other carbonaceous material; and by the fermentation of glucose by yeast. 
In the laboratory Carbon dioxide may be prepared by dropping acid on a carbonate.