Dry ice , sometimes referred to as " cardice " (mainly by British chemists), is a solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperatures than water ice and leave no residue (other than the accidental ice of atmospheric moisture). This is useful for preserving frozen foods where mechanical cooling is not available.
Dry ice sublimes at 194.65 K (-78.5 Â ° C; -109.3 ° F), at Earth's atmospheric pressure. This extreme cold makes solid substances harmless to be handled without protection due to burns caused by freezing (frostbite). Although generally not too toxic, outgassing of it can cause hypercapnia (elevated abnormal levels of carbon dioxide in the blood) due to limited site buildup.
Video Dry ice
Properti
Dry ice is a solid form of carbon dioxide (CO 2 ), a molecule consisting of a single carbon atom attached to two oxygen atoms. The dry ice is colorless, non-flammable, with a bad odor of acid, and can lower the pH of the solution when dissolved in water, forming carbonic acid (H 2 CO 3 ).
At pressures below 5.13 atm and temperatures below -56.4 ° C (-69.5 ° F) (triple point), CO 2 changes from solid to gas without liquid form intervening, through a process called sublimation. The opposite process is called deposition, where CO 2 changes from gas to solid phase (dry ice). At atmospheric pressure, sublimation/deposition occurs at -78.5 Â ° C (-109.3 Â ° F) or 194.65 K.
Dry ice density varies, but usually ranges between about 1.4 and 1.6 g/cm 3 (87 and 100 lb/cuÃ, ft). Low temperatures and direct sublimation to the gas make dry ice an effective cooler, because it is colder than water ice and leaves no residue as it changes circumstances. The sublimated enthalpy is 571 kJ/kg (25.2 kJ/mol).
Dry ice is non-polar, with zero dipole moment, so the attractive intermolecular vanm Waals style operates. The composition produces low thermal and electrical conductivity.
Maps Dry ice
History
It is generally accepted that dry ice was first observed in 1835 by the French inventor Adrien-Jean-Pierre Thilorier (1790-1844), who published his first report on substance. In his experiment, it was noted that when opening a large cylinder cover of liquid carbon dioxide, most of the liquid carbon dioxide evaporated quickly. This leaves only the dense dry ice inside the container. In 1924, Thomas B. Slate applied for a US patent to sell dry ice commercially. Furthermore, he became the first person who managed to make dry ice as an industry. In 1925, the solid form of CO 2 was trademarked by DryIce Corporation of America as "Dry Ice", thus leading to a common name. In the same year, DryIce Co. sell the material commercially for the first time; market it for cooling purposes.
The alternative name "Cardice" is a registered trademark of Air Liquide UK Ltd. Sometimes it is written as "ice card".
Producing
Dry ice is easy to make. First, a gas with a high concentration of carbon dioxide is generated. These gases can be a by-product of other processes, such as producing ammonia from nitrogen and natural gas, oil refineries or large-scale fermentation. Second, carbon dioxide-rich gases are suppressed and cooled to melt. Furthermore, the pressure is reduced. When this happens some of the liquid carbon dioxide evaporates, causing a rapid decrease in the temperature of the remaining liquid. As a result, extreme cold causes the liquid to solidify into snow. Finally, solid carbon dioxide such as snow is compressed into small pellets or larger dry ice blocks.
Dry ice is usually produced in three standard forms: large blocks, small cylinders ( 1 / 2 or 5 / 8 in pellets [13 or 16 mm] and cylindrical cylinders ( 1 / 8 inch [3.2 mm] diameter), high surface pellets to floating volume above oil or water and not attached to the skin due to their high curvature radius Small dry ice pellets are used primarily for ice blasting, rapid freezing, blackouts fire, oil compaction and have been found safe for experiments by high school students using appropriate personal protective equipment such as gloves and safety goggles The standard block weighing about 30 kg (66 lb) covered in the recorded paper wrap is the most common. It is commonly used in shipping, as they sublime relatively slowly due to the low ratio of surface area to volume meter about 1 cm (0.4 inches) and can be packed easily. This form is suitable for small-scale use, for example in grocery stores and laboratories where stored in isolated thick cases.
Apps
Commercial The most common use of dry ice is to preserve food, using non-cyclic cooling.
These are often used to package items that must be kept cool or freezing, such as ice cream or biological samples, without using mechanical cooling.
Dry ice can be used to flash food or laboratory biological samples, carbonate drinks, make ice cream, compress oil spills and stop ice sculptures and ice walls from melting.
Dry ice can be used to catch and prevent insect activity in sealed containers of grains and grain products, therefore replacing oxygen, but not altering the taste or quality of food. For the same reason, it can prevent or inhibit the oil and dietary fat become rancid.
When dry ice is placed in water, sublimation is accelerated, and thick clouds of drown smoke are formed thinly. It's used in fog machines, in theaters, haunted house attractions, and nightclubs for dramatic effects. Unlike most artificial fog machines, where the fog rises like smoke, a mist of dried ice drifts up near the ground. Dry ice is useful in the production of theater which requires a thick fog effect. The fog comes from the bulk water where dry ice is placed, and not from atmospheric water vapor (as is commonly assumed).
Sometimes it is used to freeze and remove warts. However, liquid nitrogen performs better in this role, because it is cooler so it takes less time to act, and less pressure. Dry ice has fewer problems with storage, as it can be produced from compressed carbon dioxide gas as needed.
The plumber uses equipment that forces the pressurized fluid CO 2 into the jacket around the pipe. The dried ice that is formed causes the water to freeze, forming ice plugs, allowing them to make improvements without turning off the water power. This technique can be used on pipes up to 4Ã, inch diameter (100 mm).
Dry ice can be used as a bait to trap mosquitoes, bedbugs, and other insects, because of their appeal to carbon dioxide.
It can be used to destroy rats. This is done by dropping the pellet into the rat tunnel in the ground and then closing the entrance, thus strangling the animals when the dried ice melts.
Small dry ice pellets can be used to fight fire either by cooling fuel and strangling the flame by releasing oxygen.
Extreme dry ice temperature can cause viscoelastic material to turn into glass phase. It is therefore useful to remove many types of pressure-sensitive adhesives.
Industrial
Dry ice can be used to loosen asphalt floor tiles or car lethal sounds so it is easy to get gifts, as well as frozen water in a non-valve pipe to enable repair.
One of the biggest mechanical uses of dry ice is cleaning blast. Dry ice pellets are fired from the nozzle with compressed air, combining the pellet speed with sublimation action. This can remove residues from industrial equipment. Examples of discarded materials include ink, glue, oil, paint, mold and rubber. Dry ice blasting can replace sandblasting, steam explosion, water blasting or solvent blasting. The primary environmental residue of dry ice blasting is sublimited CO 2 , thus making it a useful technique in which residues from other blasting techniques are undesirable. Recently, blast cleaning has been introduced as a method to remove smoke damage from the structure after a fire.
Dry ice is also useful for de-combustible combustible gases from storage tanks - the sublimation of dry ice pellets in discharged and disposed tanks causes an abundance of CO 2 that carries flammable vapors.
The removal and installation of cylinder liners in large engines requires the use of dry ice to cool and thereby shrink the liner so that it freely glide into the engine block. When the liner then heats up, it expands, and the resulting disturbance holds it firmly in place. Similar procedures can be used in making mechanical assemblies with high resultant strength, replacing the need for pins, locks or welds.
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.
Scientific
In the laboratory, the dried ice slurry in an organic solvent is a freezing mixture useful for cold chemical reactions and for condensation solvents in a rotary evaporator. Dry ice and acetone form cold baths -78Ã, Â ° C (-108 Ã, Â ° F; 195Ã, K), which can be used for example to prevent thermal runaway in Swern oxidation.
The process of changing cloud rainfall can be done using dry ice. It was widely used in experiments in the US in the 1950s and early 1960s before being replaced by silver iodide. Dry ice has the advantage of being relatively cheap and completely non-toxic. The main drawback is the need to be sent directly to the forbidden territory of the underdog cloud.
Dry ice bomb
"Dry ice bomb" is a tool like a balloon that uses dry ice in a sealed container like a plastic bottle. Water is usually added to accelerate the sublimation of dry ice. As the dry ice sublimes, the pressure rises, causing the bottle to burst causing a loud noise that can be avoided when the rubber stop # 3 replaces the screw cap to make a water rocket with a two-liter bottle.
The ice-dry bomb device was featured on MythBusters , episode 57 Mentos and Soda, first aired on August 9, 2006. It was also featured in an episode of Time Warp , as well as in a episode Archer .
Externalerrestrial Events
Following the flyby of Mars from the Mariner 4 spacecraft in 1966, the scientists concluded that the Martian polar caps consisted entirely of dry ice. However, the findings made in 2003 by researchers at the California Institute of Technology have shown that the Martian polar cap is almost entirely made of water ice, and the dry ice forms only a thin layer of thin, seasonal thinning seamlessly. A phenomenon called a dry ice storm is proposed to occur in the polar region of Mars. They are comparable to the Earth's lightning storm, with the crystal CO 2 taking the water in the clouds.
In 2012, the Venus Express probe from the European Space Agency detects a cold layer in the Venus atmosphere where temperatures are close to the triple point of carbon dioxide and there is the possibility that dried ice flakes are settling.
Security
Prolonged exposure to dry ice can cause severe skin damage through frostbite, and the resulting fog can also prevent attempts to withdraw from contact in a safe way. Because it sublimes into large amounts of carbon dioxide gas, which can 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 given S-phrase S9 in the laboratory safety context. Industrial dry ice may contain contaminants that make it unsafe for direct contact with foodstuffs. Small dry ice pellets used in dry ice blast cleaning do not contain any oily residue.
Source of the article : Wikipedia
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