Dry ice, sometimes referred to as “cardice” 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 out gassing from it can cause hypercapnia (abnormally elevated carbon dioxide levels in the blood) due to buildup in confined locations.
It is colorless, with a sour zesty odor, non-flammable, and slightly acidic. At pressures below 5.13 atmospheres 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. 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). 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.
Dry ice is non-polar, with a dipole moment of zero. The composition results in low thermal and electrical conductivity.
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. For this reason, dry ice is assigned the S-phrase in the context of laboratory safety. Industrial dry ice may contain contaminants that make it unsafe for direct contact with foodstuffs.
Although 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, when shipped by air or water, it is regulated as a dangerous good and IATA packing instruction 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.
In Thermocol boxes
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).
The most common use of dry ice is to preserve food without the use of mechanical cooling.
Dry ice can be used to flash freeze food, laboratory biological samples, carbonate beverages, and make ice cream.
It can be used to arrest and prevent insect activity in closed containers of grains and grain products.
This is used in fog machines, at theaters, discothèques, haunted house attractions, and nightclubs for dramatic effects. Dry ice is useful in theater productions that require dense fog effects.
Dry ice can be used as bait to trap mosquitoes, bedbugs, and other insects.
One of the largest mechanical uses of dry ice is blast cleaning. Dry ice pellets are shot out of 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 being removed include ink, glue, oil, paint, mold and rubber.
Recently, blast cleaning has been introduced into the industry of removing smoke damage from structures after fires.
Dry ice is also useful for the de-gassing of flammable vapors from storage tanks.
The removal and fitting of cylinder liners in large marine engines requires the use of dry ice to chill.
Similar procedures may be used in fabricating mechanical assemblies with a high resultant strength, replacing the need for pins, keys or welds.
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.