Dry ice
Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimes directly from the solid state to the gas state. It is used primarily as a cooling agent, but is also used in fog machines at theatres for dramatic effects. 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 (such as ice cream) where mechanical cooling is unavailable.
Dry ice sublimes at Template:Convert at Earth atmospheric pressure. This extreme cold makes the solid dangerous to handle without protection from frostbite injury. 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.
Properties
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Dry ice is the solid form of carbon dioxide (CO2), a molecule consisting of a single carbon atom bonded to two oxygen atoms. Dry ice is colorless, odorless, and non-flammable, and can lower the pH of a solution when dissolved in water, forming carbonic acid (H2CO3).<ref name="Yaws 2001 p=125">Template:Harvnb</ref>
At pressures below 5.13 atm and temperatures below Template:Convert (the triple point), CO2 changes from a solid to a gas with no intervening liquid form, through a process called sublimation.Template:Efn The opposite process is called deposition, where CO2 changes from the gas to solid phase (dry ice). At atmospheric pressure, sublimation/deposition occurs at Template:Convert.<ref>Template:Cite journal</ref>
The density of dry ice increases with decreasing temperature and ranges between about Template:Convert below Template:Convert.<ref>Template:Cite journal</ref> 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.<ref>Template:Harvnb</ref> Its enthalpy of sublimation is 571 kJ/kg (25.2 kJ/mol, 136.5 calorie/g).
Dry ice is non-polar, with a dipole moment of zero, so attractive intermolecular van der Waals forces operate.<ref>Template:Harvnb</ref> The composition results in low thermal and electrical conductivity.<ref>Template:Harvnb</ref>
History
[edit]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.<ref>Template:Cite journal See also: "Solidification of carbonic acid," Template:Webarchive The London and Edinburgh Philosophical Magazine, 8 : 446–447 (1836).</ref><ref>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, …" Template:Webarchive (For the improvement of a machine to compress gas, …), Description des Machines et Procédés consignés dans les brevets d'invention, 30 : 251–267 (1836).</ref> 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.<ref name="Industry Dry ice">Template:Cite journal</ref> In 1925, this solid form of CO2 was trademarked by the DryIce Corporation of America as "Dry ice", leading to its common name.<ref name="About Dry ice">Template:Cite book</ref> That same year the DryIce Co. sold the substance commercially for the first time, marketing it for refrigeration purposes.<ref name="Industry Dry ice" />
Manufacture
[edit]Dry ice is easily manufactured.<ref>Template:Cite web</ref><ref name="uigi">Template:Cite web</ref> The most common industrial method of manufacturing dry ice starts with a gas having a high concentration of carbon dioxide. Such gases can be a byproduct of another process, such as producing ammonia from nitrogen and natural gas, oil refinery activities or large-scale fermentation.<ref name = "uigi" /> Second, the carbon dioxide-rich gas is pressurized and refrigerated until it liquefies. 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 small pellets or larger blocks of dry ice.<ref>Good plant design and operation for onshore carbon capture installations and onshore pipelines Template:Webarchive. The Energy Institute. London. September 2010. p. 10</ref><ref name="hsw"/>
Dry ice is typically produced in three standard forms: large blocks, small (Template:Cvt diameter) cylindrical pellets and tiny (Template:Convert diameter) cylindrical, high surface to volume pellets that float on oil or water and do not stick to skin because of their high radii of curvature. Tiny dry ice pellets are used primarily for dry ice blasting, quick freezing, fire fighting, oil solidifying and have been found to be safe for experimentation by middle school students wearing appropriate personal protective equipment such as gloves and safety glasses. A standard block weighing approximately Template:CvtTemplate:Citation needed covered in a taped paper wrapping 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 Template:Convert 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.<ref>Template:Cite web</ref> Density of pellets is 60–70% of the density of blocks.<ref>Template:Cite web</ref>
Dry ice is also produced as a byproduct of cryogenic air separation, an industry primarily concerned with manufacturing extremely cold liquids such as liquid nitrogen and liquid oxygen. In this process, carbon dioxide liquefies or freezes at a far higher temperature compared to that needed to liquefy nitrogen and oxygen. The carbon dioxide must be removed during the process to prevent dry ice from fouling the equipment, and once separated can be processed into commercial dry ice in a manner similar to that described above.
Applications
[edit]Commercial
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The most common use of dry ice is to preserve food,<ref name="Yaws 2001 p=125"/> using non-cyclic refrigeration.
It is frequently used to package items that must remain cold or frozen, such as ice cream or biological samples, in the absence of availability or practicality of mechanical cooling.
Dry ice is critical in the deployment of some vaccines, which require storage at ultra-cold temperatures along their supply line.<ref>Template:Cite news</ref>
Dry ice can be used to flash-freeze food<ref name=flashfreeze>Template:Cite web</ref> or laboratory biological samples,<ref>Template:Cite web</ref> carbonate beverages,<ref name=flashfreeze/> make ice cream,<ref>Template:Cite news</ref> solidify oil spills<ref>"Zapping Oil Spills with Dry Ice and Ingenuity" by Gordon Dillow Los Angeles Times South Bay section page 1 2/24/1994</ref> and stop ice sculptures and ice walls from melting.
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.
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 theatres, 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.<ref name="hsw">Template:Cite web</ref> Dry ice is useful in theatre productions that require dense fog effects.<ref>Template:Harvnb</ref> The fog originates from the bulk water into which the dry ice is placed, and not from atmospheric water vapor (as is commonly assumed).<ref>Template:Cite journal</ref>
It is occasionally used to freeze and remove warts.<ref>Template:Cite journal</ref> However, liquid nitrogen performs better in this role, as it is colder, thereby requiring less time to act, and needs less pressure to store.<ref name=aa1317 /> Dry ice has fewer problems with storage, since it can be generated from compressed carbon dioxide gas as needed.<ref name=aa1317>Template:Harvnb</ref>
In plumbing, dry ice is used to cut off water flow to pipes to allow repairs to be made without shutting off water mains. Pressurised liquid CO2 is forced into a jacket wrapped around a pipe, which in turn causes the water inside to freeze and block the pipe. When the repairs are done, the jacket is removed and the ice plug melts, allowing the flow to resume. This technique can be used on pipes up to 4 inches or 100 mm in diameter.<ref name="plumbing2">Template:Harvnb</ref>
Dry ice can be used as bait to trap mosquitoes, bedbugs, and other insects, due to their attraction to carbon dioxide.<ref>Template:Cite journal</ref>
It can be used to exterminate rodents. This is done by dropping pellets into rodent tunnels in the ground and then sealing off the entrance, thus suffocating the animals as the dry ice sublimates.<ref>Template:Cite news</ref>
Tiny dry ice pellets can be used to fight fire by both cooling fuel and suffocating the fire by excluding oxygen.<ref>"Could a Freeze Gun Put Flames on Ice" by Zantos Peabody Los Angeles Times local section B3 9/3/2002</ref>
The extreme temperature of dry ice can cause viscoelastic materials to change to glass phase. Thus, it is useful for removing many types of pressure sensitive adhesives.
Industrial
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Dry ice can be used for loosening asphalt floor tiles or car sound deadening material, making them easy to prise off,<ref name=PM169>Template:Cite journal</ref> as well as freezing water in valveless pipes to enable repair.<ref name=PM159>Template:Cite journal</ref>
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.<ref>Template:Cite news</ref> 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.<ref>Template:Cite web</ref>
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.<ref>Template:Cite web</ref>
Dry ice has found its application in construction for freezing soil, serving as an effective alternative to liquid nitrogen.<ref>Template:Cite journal</ref> This method reduces the soil temperature to approximately -70 to -74 °C, rapidly freezing the groundwater. As a result, the soil's strength and impermeability significantly increase,<ref>Template:Cite journal</ref> which is essential for the safe execution of underground construction projects.<ref>Template:Cite journal</ref>
It is also useful as a cutting fluid.
Scientific
[edit]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.<ref name="House">Template:Harvnb</ref> Dry ice and acetone forms a cold bath of Template:Cvt, 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.<ref name=Keyescs /> It was widely used in experiments in the US in the 1950s and early 1960s before it was replaced by silver iodide.<ref name=Keyescs /> Dry ice has the advantage of being relatively cheap and completely non-toxic.<ref name=Keyescs /> Its main drawback is the need to be delivered directly into the supercooled region of clouds being seeded.<ref name=Keyescs>Template:Harvnb</ref>
Dry ice bombs
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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 with a loud noise. The screw cap can be replaced with a rubber stopper to make a water rocket.
The dry ice bomb device was featured on MythBusters, episode 57 Mentos and Soda, which first aired on August 9, 2006.<ref>Template:Cite web</ref> It was also featured in an episode of Time Warp, as well as in an episode of Archer.
Extraterrestrial occurrence
[edit]Following the Mars flyby of the Mariner 4 spacecraft in 1966, scientists concluded that Mars' polar caps consist entirely of dry ice.<ref name="NGMars">Template:Cite book</ref> 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.<ref name="NGMars"/><ref name="ScienceJournal">Template:Cite journal</ref> 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.<ref name="NGMars2">Template:Cite book</ref> Dry ice is also proposed as a mechanism for the geysers on Mars.<ref name=LPS2006>Template:Cite web</ref>
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.<ref>"A curious cold layer in the atmosphere of Venus". Template:Webarchive. European Space Agency (1 October 2012).</ref>
Observations from the Uranus flyby by Voyager 2 indicates that dry ice is present on the surface of its large moons Ariel,<ref name="Grundy Young et al. 2006">Template:Cite journal</ref> Umbriel<ref name="Grundy Young et al. 2006" /> and Titania.<ref name="Grundy Young et al. 2006" /> Scientists speculate that the magnetic field of Uranus contributes to the generation of CO2 ice on the surfaces of its moons.<ref name="CartwrightEmery2015">Template:Cite journal</ref> Voyager 2 observations of Neptune's moon Triton suggested the presence of dry ice on the surface, though followup observations indicate that the carbon ices on the surface are carbon monoxide but that the moon's crust is composed of a significant quantity of dry ice.<ref name="Lellouchde Bergh2010">Template:Cite journal</ref>
Safety
[edit]Template:Further Template:Chembox 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.<ref name=PM169 /> For this reason, in the context of laboratory safety dry ice is assigned label precaution Template:GHS phrases/inline Industrial dry ice may contain contaminants that make it unsafe for direct contact with food.<ref>Template:Cite web</ref>Template:Failed verification Tiny dry ice pellets used in dry ice blast cleaning do not contain oily residues.
Dry ice is assigned a UN number, a code for hazardous substances: UN 1845.<ref name="Lion Technology-2019">Template:Cite web</ref> Dry ice is not classified as a dangerous substance by the European Union, or as a hazardous material by the United States Department of Transportation for ground transportation.<ref name="32008R1272">Template:Cite web</ref><ref name="Lion Technology-2019" /> However, in the US, it is regulated as a dangerous good when shipped by air or water. International Air Transport Association (IATA) regulations require specific diamond-shaped black-and white labelling to be placed on the package. The package must have adequate ventilation so that it will not rupture from pressure in the event that the Dry Ice begins to sublime in the packaging.<ref name="Lion Technology-2019" /> The Federal Aviation Administration in the US allows airline passengers to carry up to Template:Cvt per person either as checked baggage or carry-on baggage, when used to refrigerate perishables.<ref>Template:Cite web</ref>
At least one person has been killed by carbon dioxide gas subliming off dry ice in coolers placed in a car.<ref>Template:Cite web</ref> In 2020, three people were killed at a party in Moscow after 25 kg of dry ice was dumped in a pool; carbon dioxide is heavier than air, and so can linger near the ground, just above water level.<ref>Template:Cite web</ref>
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Dry ice pellet subliming in water, releasing thick white fog
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A UN 1845 label for dry ice
Drink
[edit]Dry ice is sometimes used to give a fog effect to cocktails. One bar patron who accidentally ingested pellets from a drink suffered severe burns to his esophagus, stomach, and duodenum, causing permanent problems with eating.<ref>Template:Cite web</ref><ref>Template:Cite journal</ref> Rapid sublimation could cause gas buildup that ruptures digestive organs or suffocation. Products that contain dry ice and prevent it from being accidentally ingested eliminate these risks while producing the desired fog effect.<ref>Template:Cite web</ref>
Footnotes
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