Carbon dioxide

• BPCarbon Dioxide
• JPCarbon Dioxide
• Ph. Eur.Carbon Dioxide
• USP–NFCarbon Dioxide

Carbonei dioxidum; carbonic acid gas; carbonic anhydride; dry ice (solid form); E290

Carbon dioxide · [124-38-9]

UNII 142M471B3J · PubChem CID 280

CO2 · 44.01

Propellant / inert gas

Typical concentrations: — · Dosage forms: Liquid

Used as an inert gas to displace air from the headspace of ampoules, vials and liquid containers and to blanket oxygen-sensitive products during manufacture, and as a propellant for topical aerosols. It is generated in situ in effervescent tablets and granules by the reaction of an acid with a carbonate. Supercritical carbon dioxide is used for extraction and for particle engineering, and the solid (dry ice) is used for cooling.

A colourless, odourless, non-flammable gas with a faintly acidic taste. It is supplied as a liquefied gas under pressure in cylinders, or as a solid.

Sublimation point

−78.5 °C at atmospheric pressure (the solid sublimes without melting)

Critical point

≈ 31.1 °C and 7.38 MPa

Gas density

≈ 1.98 g/L at 0 °C and 101.3 kPa (about 1.5 times that of air)

Solubility

moderately soluble in water, giving a weakly acidic solution of carbonic acid

Chemically stable and inert under normal conditions. Store cylinders in a cool, well-ventilated place away from heat.

Reacts with alkalis and alkaline solutions to form carbonates, and with reactive metals such as magnesium and sodium at high temperatures. Dissolved carbon dioxide lowers the pH of aqueous solutions and may precipitate drugs that are less soluble at lower pH.

Recovered as a by-product of fermentation, ammonia and hydrogen production, or from combustion gases and natural sources, then purified, dried and liquefied by compression and cooling.

Not toxic at low concentrations, but it is an asphyxiant at high concentrations: raised levels cause headache, rapid breathing and dizziness, and very high levels cause loss of consciousness. The occupational exposure limit is 5000 ppm (8-hour TWA). Contact with the solid or rapidly expanding liquid causes cold burns.

Handle cylinders according to compressed-gas safety rules and use only in well-ventilated areas, since the gas is heavier than air and collects in low places. Wear insulated gloves and eye protection when handling dry ice or the liquid.

GRAS listed. Accepted as a food additive in Europe (E290). Included in medicines licensed in Europe.

Nitrogen; nitrous oxide.

As an aerosol propellant it behaves as a compressed gas, but because part of it dissolves in the product the fall in pressure as the container empties is smaller than with nitrogen. In effervescent products the amount of carbon dioxide released depends on the stoichiometry and moisture content of the acid–carbonate couple.