Dry ice

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Small pellets of dry ice subliming in air
Crystal structure of dry ice

Dry ice, sometimes referred to as "cardice" (chiefly by British chemists), is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue (other than incidental frost from moisture in the atmosphere). It is useful for preserving frozen foods, ice cream, etc., where mechanical cooling is unavailable.

Dry ice sublimes at −78.5 °C (−109.3 °F) at Earth atmospheric pressures. This extreme cold makes the solid dangerous to handle without protection due to burns caused by freezing (frostbite). While generally not very toxic, the outgassing from it can cause hypercapnia (abnormally elevated carbon dioxide levels in the blood) due to buildup in confined locations.


For supplementary chemical data, see Carbon dioxide data.

Dry ice is the solid form of carbon dioxide (chemical formula CO2), comprising two oxygen atoms bonded to a single carbon atom. It is colorless, with a sour zesty odor, non-flammable, and slightly acidic.[1]

Comparison of phase diagrams of carbon dioxide (red) and water (blue) as a log-lin chart with phase transitions points at 1 atmosphere

At pressures below 5.13 atm and temperatures below −56.4 °C (−69.5 °F) (the triple point), CO2 changes from a solid to a gas with no intervening liquid form, through a process called sublimation.[note 1] The opposite process is called deposition, where CO2 changes from the gas to solid phase (dry ice). At atmospheric pressure, sublimation/deposition occurs at −78.5 °C (−109.3 °F).

The density of dry ice varies, but usually ranges between about 1.4 and 1.6 g/cm3 (87 and 100 lb/cu ft).[2] The low temperature and direct sublimation to a gas makes dry ice an effective coolant, since it is colder than water ice and leaves no residue as it changes state.[3] Its enthalpy of sublimation is 571 kJ/kg (25.2 kJ/mol).

Dry ice is non-polar, with a dipole moment of zero, so attractive intermolecular van der Waals forces operate.[4] The composition results in low thermal and electrical conductivity.[5]


It is generally accepted that dry ice was first observed in 1835 by French inventor Adrien-Jean-Pierre Thilorier (1790–1844), who published the first account of the substance.[6][7] In his experiments, he noted that when opening the lid of a large cylinder containing liquid carbon dioxide, most of the liquid carbon dioxide quickly evaporated. This left only solid dry ice in the container. In 1924, Thomas B. Slate applied for a US patent to sell dry ice commercially. Subsequently, he became the first to make dry ice successful as an industry.[8] In 1925, this solid form of CO2 was trademarked by the DryIce Corporation of America as "Dry ice", thus leading to its common name.[9] That same year the DryIce Co. sold the substance commercially for the first time; marketing it for refrigerating purposes.[8]

The alternative name "Cardice" is a registered trademark of Air Liquide UK Ltd.[10] It is sometimes written as "card ice".[11]


Sublimation of dry ice when placed on the surface of water at room temperature

Dry ice is easily manufactured.[12][13] First, gases with a high concentration of carbon dioxide are produced. Such gases can be a byproduct of another process, such as producing ammonia from nitrogen and natural gas, or large-scale fermentation.[13] Second, the carbon dioxide-rich gas is pressurized and refrigerated until it liquifies. Next, the pressure is reduced. When this occurs some liquid carbon dioxide vaporizes, causing a rapid lowering of temperature of the remaining liquid. As a result, the extreme cold causes the liquid to solidify into a snow-like consistency. Finally, the snow-like solid carbon dioxide is compressed into either small pellets or larger blocks of dry ice.[14][15]

A teaching laboratory demonstration for the production of dry ice is to use a carbon dioxide fire extinguisher with a porous fabric collecting bag over the nozzle. The expansion of the gas lowers the temperature enough to produce dry ice snow that is collected in the bag. This is an inefficient process, and unsuitable for even lab-scale production. The expansion is inefficient, fire extinguishers are an expensive way to buy carbon dioxide, and there is the safety risk that extinguishers are left empty and not refilled.

Dry ice is typically produced in two standard forms: blocks and cylindrical pellets. A standard block weighing approximately 30 kg[citation needed] is most common. These are commonly used in shipping, because they sublime relatively slowly due to a low ratio of surface area to volume. Pellets are around 1 cm (0.4 in) in diameter and can be bagged easily. This form is suited to small scale use, for example at grocery stores and laboratories where it is stored in a thickly insulated chest.[16]



An ice cream cart

The most common use of dry ice is to preserve food,[1] using non-cyclic refrigeration.

It is frequently used to package items that must remain cold or frozen, such as ice cream or biological samples, without the use of mechanical cooling.

Dry ice can be used to flash-freeze food[17] or laboratory biological samples,[18] carbonate beverages,[17] and make ice cream.[19]

Dry ice can be used to arrest and prevent insect activity in closed containers of grains and grain products, as it displaces oxygen, but does not alter the taste or quality of foods. For the same reason, it can prevent or retard food oils and fats from becoming rancid.

Dry ice in water

When dry ice is placed in water, sublimation is accelerated, and low-sinking, dense clouds of smoke-like fog are created. This is used in fog machines, at theaters, haunted house attractions, and nightclubs for dramatic effects. Unlike most artificial fog machines, in which fog rises like smoke, fog from dry ice hovers near the ground.[15] Dry ice is useful in theater productions that require dense fog effects.[20] The fog originates from the bulk water into which the dry ice is placed, and not from atmospheric water vapor (as is commonly assumed).[21]

It is occasionally used to freeze and remove warts.[22] However, liquid nitrogen performs better in this role, since it is colder so requires less time to act, and less pressure.[23] Dry ice has fewer problems with storage, since it can be generated from compressed carbon dioxide gas as needed.[23]

Plumbers use equipment that forces pressurised liquid CO2 into a jacket around a pipe. The dry ice formed causes the water to freeze, forming an ice plug, allowing them to perform repairs without turning off the water mains. This technique can be used on pipes up to 4 inches (100 mm) in diameter.[24]

Dry ice can be used as bait to trap mosquitoes, bedbugs, and other insects, due to their attraction to carbon dioxide.[25]


Dry ice blasting used for cleaning a rubber mold

Dry ice can be used for loosening asphalt floor tiles or car sound deadening material making it easy to pry off,[26] as well as freezing water in valveless pipes to enable repair.[27]

One of the largest mechanical uses of dry ice is blast cleaning. Dry ice pellets are shot from a nozzle with compressed air, combining the power of the speed of the pellets with the action of the sublimation. This can remove residues from industrial equipment. Examples of materials removed include ink, glue, oil, paint, mold and rubber. Dry ice blasting can replace sandblasting, steam blasting, water blasting or solvent blasting. The primary environmental residue of dry ice blasting is the sublimed CO2, thus making it a useful technique where residues from other blasting techniques are undesirable.[28] Recently, blast cleaning has been introduced as a method of removing smoke damage from structures after fires.

Dry ice is also useful for the de-gassing of flammable vapours from storage tanks — the sublimation of dry ice pellets inside an emptied and vented tank causes an outrush of CO2 that carries with it the flammable vapours.[29]

The removal and fitting of cylinder liners in large engines requires the use of dry ice to chill and thus shrink the liner so that it freely slides into the engine block. When the liner then warms up, it expands, and the resulting interference fit holds it tightly in place. Similar procedures may be used in fabricating mechanical assemblies with a high resultant strength, replacing the need for pins, keys or welds.[30]

Dry-ice blasting, a form of carbon dioxide cleaning, is used in a number of industrial applications.

It is also useful as a cutting fluid.


In laboratories, a slurry of dry ice in an organic solvent is a useful freezing mixture for cold chemical reactions and for condensing solvents in rotary evaporators.[31] Dry ice/acetone forms a cold bath of –78 °C, which can be used for instance to prevent thermal runaway in a Swern oxidation.

The process of altering cloud precipitation can be done with the use of dry ice.[32] It was widely used in experiments in the US in the 1950s and early 60s before it was replaced by silver iodide.[32] Dry ice has the advantage of being relatively cheap and completely non-toxic.[32] Its main drawback is the need to be delivered directly into the supercooled region of clouds being seeded.[32]

Dry ice bombs

Main article: Dry ice bomb

A "dry ice bomb" is a balloon-like device using dry ice in a sealed container such as a plastic bottle. Water is usually added to accelerate the sublimation of the dry ice. As the dry ice sublimes, pressure increases, causing the bottle to burst.

The device was featured on MythBusters, episode 57 Mentos and Soda, which first aired on August 9, 2006.[33] It was also featured in an episode of Time Warp.

Extraterrestrial occurrence

Following the Mars flyby of the Mariner 4 spacecraft in 1966, scientists concluded that Mars' polar caps consist entirely of dry ice.[34] However, findings made in 2003 by researchers at the California Institute of Technology have shown that Mars' polar caps are almost completely made of water ice, and that dry ice only forms a thin surface layer that thickens and thins seasonally.[34][35] A phenomenon named dry ice storms was proposed to occur over the polar regions of Mars. They are comparable to Earth's thunderstorms, with crystalline CO2 taking the place of water in the clouds.[36]

In 2012, the European Space Agency's Venus Express probe detected a cold layer in the atmosphere of Venus where temperatures are close to the triple point of carbon dioxide and it is possible that flakes of dry ice precipitate.[37]


Dry ice pellet subliming in water

Prolonged exposure to dry ice can cause severe skin damage through frostbite, and the fog produced may also hinder attempts to withdraw from contact in a safe manner. Because it sublimes into large quantities of carbon dioxide gas, which could pose a danger of hypercapnia, dry ice should only be exposed to open air in a well-ventilated environment.[26] For this reason, dry ice is assigned the S-phrase S9 in the context of laboratory safety. Industrial dry ice may contain contaminants that make it unsafe for direct contact with foodstuffs.[38]

Although dry ice is not classified as a dangerous substance by the European Union,[39] or as a hazardous material by the United States Department of Transportation for ground transportation, when shipped by air or water, it is regulated as a dangerous good and IATA packing instruction 954 (IATA PI 954) requires that it be labeled specially, including a diamond-shaped black-and white label, UN 1845. Also, arrangements must be in place to ensure adequate ventilation so that pressure build-up does not rupture the packaging.[40] The Federal Aviation Administration in the US allows airline passengers to carry up to 2.5 kg per person either as checked baggage or carry-on baggage, when used to refrigerate perishables.[41]

Notes and references


  1. Above the triple point, CO2 goes through the more familiar transitions via a liquid phase.


  1. 1.0 1.1 Yaws 2001, p. 125
  2. Häring 2008, p. 200
  3. Yaws 2001, p. 124
  4. Khanna & Kapila 2008, p. 161
  5. Khanna & Kapila 2008, p. 163
  6. Thilorier (1835). "Solidification de l'Acide carbonique". Comptes rendus (in French). 1: 194–196.  See also: "Solidification of carbonic acid," The London and Edinburgh Philosophical Magazine, 8 : 446-447 (1836).
  7. Note:
    • The Bulletin des Lois du Royaume de France (Bulletin of the laws of the kingdom of France), 9th series, part ii, no. 92, page 74 (February 1832) lists: "24° M. Thilorier (Adrien-Jean-Pierre) employé à l'administration des postes, demeurant à Paris, place Vendôme, no 21, auquel il a été délivré le 16 mai dernier, le certificat de sa demande d'un brevet d'invention de dix ans pour le perfectionnement d'une machine à comprimer le gaz; …" (24th Mr. Thilorier (Adrien-Jean-Pierre) employed at the Post Office, residing in Paris, Place Vendôme, no. 21, where was delivered May 16th last, the certificate, by his request, for a patent of invention for ten years for the improvement of a machine to compress gas; … )
    • In a patent (no. 2896) which was filed on May 16, 1831 and which was published in 1836, Adrien-Jean-Pierre Thilorier, an employee of the French "Administration des postes" (i.e., Post Office) in Paris is identified explicitly as the inventor of a machine for compressing gases which in 1829 won the French Academy of Sciences' Montyon prize for mechanics. The patent describes the machine and its performance in detail. See: (French Ministry of Commerce), "Pour le perfectionnement d'une machine à comprimer le gaz, …" (For the improvement of a machine to compress gas, …), Description des Machines et Procédés consignés dans les brevets d'invention, … , 30 : 251-267 (1836).
  8. 8.0 8.1 Killeffer, D.H. (October 1930). "The Growing Industry-Dry-Ice". Industrial & Engineering Chemistry. Industrial & Engineering Chemistry. 22 (10): 1087. doi:10.1021/ie50250a022. 
  9. The Trade-mark Reporter. United States Trademark Association. 1930. ISBN 1-59888-091-8. 
  10. "Case details for Trade Mark 516211". UK Intellectual Property Office. Retrieved 2009-07-25. 
  11. Treloar 2003, p. 175
  12. "What is Dry Ice?". Continental Carbonic Products, Inc. Retrieved 2009-07-26. 
  13. 13.0 13.1 "Carbon Dioxide (CO2) Properties, Uses, Applications: CO2 Gas and Liquid Carbon Dioxide". Universal Industrial Gases, Inc. Retrieved 2009-07-26. 
  14. Good plant design and operation for onshore carbon capture installations and onshore pipelines. The Energy Institute. London. September 2010. p. 10
  15. 15.0 15.1 "How does dry ice work?". HowStuffWorks. Retrieved 2009-07-26. 
  16. "Dry Ice Sales - How to sell Dry Ice". dryiceinfo.com. Retrieved 6 July 2015. 
  17. 17.0 17.1 "Cool Uses for Dry Ice". Airgas.com. Retrieved 2009-07-25. 
  18. "Preparing Competent E. coli with RF1/RF2 solutions". Personal.psu.edu. Retrieved 2009-07-25. 
  19. Blumenthal, Heston (2006-10-29). "How to make the best treacle tart and ice cream in the world". London: The Sunday Times. Retrieved 2007-06-12. 
  20. McCarthy 1992
  21. Kuntzleman, Thomas S.; Ford, Nathan; No, Jin-Hwan; Ott, Mark E. (2015-04-14). "A Molecular Explanation of How the Fog Is Produced when Dry Ice Is Placed in Water". Journal of Chemical Education. 92 (4): 643–648. Bibcode:2015JChEd..92..643K. ISSN 0021-9584. doi:10.1021/ed400754n. 
  22. Lyell A. (1966). "Management of warts". British Medical Journal. 2 (5529): 1576–9. PMC 1944935Freely accessible. PMID 5926267. doi:10.1136/bmj.2.5529.1576. 
  23. 23.0 23.1 Goroll & Mulley 2009, p. 1317
  24. Treloar 2003, p. 528
  25. Reisen WK, Boyce K, Cummings RC, Delgado O, Gutierrez A, Meyer RP, Scott TW. (1999). "Comparative effectiveness of three adult mosquito sampling methods in habitats representative of four different biomes of California". J Am Mosq Control Assoc. 15 (1): 24–31. PMID 10342265. 
  26. 26.0 26.1 Horrell, Bill (February 1961). "Dry ice pops off Asphalt Tile". Popular Mechanics. 115 (2): 169. 
  27. Mundis, Warren J. (July 1960). "Dry Ice as a Plumbing Aid". Popular Science. 177 (1): 159. 
  28. Wolcott, John (January 2008). "Ice-blasting firm offers a cool way to clean up". The Daily Herald. Archived from the original on January 9, 2008. Retrieved 2008-01-20. 
  29. "All About Ice – Ice Carvings, Vodka Luges, Crushed and Dry Ice". allaboutice.com. Retrieved 6 July 2015. 
  30. "Bushing and Plain Bearings Press or Shrink Fit Design and Application - Engineers Edge". engineersedge.com. Retrieved 6 July 2015. 
  31. Housecroft 2001, p. 410
  32. 32.0 32.1 32.2 32.3 Keyes 2006, p. 83
  33. "Mythbusters episode 57". mythbustersresults.com. 
  34. 34.0 34.1 Mars Poles Covered by Water Ice, Research Shows. National Geographic. 13 February 2003. Retrieved 2009-07-26. 
  35. Byrne, S.; Ingersoll, AP (2003-02-14). "A Sublimation Model for Martian South Polar Ice Features". Science. American Association for the Advancement of Science. 299 (5609): 1051–3. Bibcode:2003Sci...299.1051B. PMID 12586939. doi:10.1126/science.1080148. Retrieved 2009-07-30. 
  36. Dry Ice Storms May Pelt Martian Poles, Experts Say. National Geographic. 19 December 2005. Retrieved 2009-07-26. 
  37. A curious cold layer in the atmosphere of Venus. European Space Agency (1 October 2012).
  38. Nelson, Lewis (2000). "Carbon Dioxide Poisoning". Emergency Medicine. Retrieved 2009-07-28. 
  39. "Regulation (EC) No 1272/2008 of the European Parliament". Retrieved 2009-07-31. 
  40. Requirements for Shipping Dry Ice (IATA PI 954). Environmental Resource Center. 24 May 2006. Retrieved 2009-07-31. 
  41. "Hazardous Materials Information for Passengers" (PDF). Retrieved 2009-07-26.  available on the FAA website: http://www.faa.gov/