Nomenclature
CAS number: 124-38-9
Carbonic acid gas; carbonic anhydride.
CO
2; mol wt 44.01.
C 27.29%, O 72.71%.
Description and references
Occurs in the atms of many planets. In our
solar system, e.g., on Venus, the optical layer thickness due to CO2 is 100,000 cm/atm, but only 220 cm/atm on Earth. Analyses
of air in the temperate zones of the Earth show 0.027 to 0.036% (v/v)
of CO2: G. P. Kuiper, The Atmospheres
of the Earth and the Planets (Univ. of Chicago Press,
1949); Landolt-Bornstein, Zahlenwerte vol. III (Springer-Verlag, 6th ed., 1952) pp 59 and 585.
Constituent of carbonate type of minerals and products of animal
metabolism. Necessary for the respiration cycle of plants and animals.
Obtained industrially as a by-product in the manuf of lime during
the “burning” of limestone (CaCO3). Also produced by burning
coke or other carbonaceous material. In the U.S.A. large amounts
are produced by fermentation (Backus process and Reich process).
When glucose is fermented by yeast, the chief products are ethyl alcohol
and CO2. Prepd in the laboratory by dropping acid on a
carbonate: E. H. Archibald, The Preparation
of Pure Inorganic Substances (Wiley, New York, 1932) p
196; Loomis, Walters, J. Am. Chem. Soc. 48, 3103 (1926). Purification: Glemser in Handbook of Preparative Inorganic Chemistry G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) p 647.
Discovery of a second polymorph of dry ice: L.-G. Liu, Nature 303, 508 (1983). Reviews: E. L. Quinn, J. Chem. Educ. 7, 151-162 and 403-419 (1930); J. Kuprianoff, Die feste Kohlens"aure (Trockeneis) (Enke,
Stuttgart, 1939); E. L. Quinn, C. L. Jones, Carbon Dioxide (Reinhold, New York, 1947); W. R. Ballou,
in Kirk-Othmer Encyclopedia of Chemical Technology vol. 4 (Interscience, New York, 3rd ed., 1978) pp 725-742.
Reviews of supercritical CO2 (scCO2) solvent uses and environmental benefits in polymer chemistry:
S. L. Wells, J. DeSimone, Angew. Chem. Int.
Ed. 40, 518-527 (2001); in catalysis: W. Leitner, Acc. Chem. Res. 35, 746-756 (2002).
Properties
Colorless, odorless gas. Non-flammable. Faint acid taste. Usually a nonsupporter
of combustion, athough burning magnesium continues to burn when transferred
into a CO2 atm. Usually marketed in steel cylinders (under
sufficient pressure to keep it liquid) or in solid form as Dry Ice (compressed carbon dioxide snow, d 1.35). When shipped in steel cylinders, CO2 is in the form of gas over liquid and at 20° exerts a pressure
of 830 psi. Use gloves when handling dry ice, as its temp is at least -78.5°;
momentary skin contact with dry ice has caused serious frostbites
and blisters. At atmospheric pressures the solid form changes into
the gaseous phase without liquefaction. d (gas) 1.527 (air = 1); d (gas) 1.557 (N2 = 1); abs d 0.1146 lb/cu ft at 25°; vol at
25°: 8.76 cu ft/lb. d (gas, 0°) 1.976 g/l at 760 mm; d (liq, 0°) 0.914 at 34.3 atm; d (solid, -56.6°) 1.512. Sublimes at -78.48° (760 mm). mp5.2 atm -56.6°. The gas is not affected by heat until temp reaches about
2000°. Crit temp 31.3°; crit press 72.9 atm; crit density 0.464.
Triple point -56.6° at 5.11 atm. Vapor press at -120°: 10.5 mm;
at -100°: 104.2 mm; at -82°: 569.1 mm. Heat of formation 94.05
kcal/mol. Latent heat of vaporization 83.12 g cal/g. Specific heat
0.19 to 0.21 Btu/lb. Soly in water (ml CO2/100 ml H2O at 760 mm): 0° = 171; 20° = 88; 60° = 36. More sol at
higher pressures. Less sol in alcohol, other neutral organic solvents.
Absorbed by alkaline solns with the formation of carbonates.Caution
Potential symptoms of overexposure
are headache, dizziness, restlessness and paresthesia; dyspnea; sweating,
malaise; increased heart rate and cardiac output; elevated blood pressure;
coma; asphyxia; convulsions; direct contact with liquid or dry ice
may cause frostbite. See NIOSH
Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997)
p 52.Use
In the carbonation of beverages; manuf of carbonates;
in fire prevention and extinction; for inerting flammable materials
during manuf, 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 CO
2 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.
Therapeutic Category
Respiratory stimulant.
Therapeutic Category (Veterinary)
Respiratory stimulant (inhalant).
Keywords
Respiratory Stimulant