Information AboutDry Ice |
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Carbon dioxide is an atmospheric Gas comprised of one Carbon and two Oxygen atoms. A very widely known Chemical Compound , it is frequently known by its formula '''CO2'''. In its Solid state, it is commonly called '''dry ice'''. Atmospheric carbon dioxide derives from multiple natural sources including Volcanic outgassing, the Combustion of Organic Matter , and the Respiration processes of living aerobic organisms; man-made sources of carbon dioxide come mainly from the burning of various fossil fuels for Power Generation and Transport use. It is also produced by various Microorganism s from Fermentation and Cellular Respiration . Plant s utilize carbon dioxide during Photosynthesis , using both the carbon and the oxygen to construct Carbohydrate s. In addition, plants also release oxygen to the atmosphere, which is subsequently used for respiration by Heterotrophic organisms, forming a Cycle . It is present in the Earth's Atmosphere at a low concentration and acts as a Greenhouse Gas . It is a major component of the Carbon Cycle . CHEMICAL AND PHYSICAL PROPERTIES Carbon dioxide is a Colour less gas which, when inhaled at high concentrations (a dangerous activity because of the associated Asphyxiation risk), produces a sour taste in the mouth and a stinging sensation in the nose and throat. These effects result from the gas dissolving in the Mucous Membranes and Saliva , forming a weak solution of Carbonic Acid . Its density at 25 °C is 1.98 kg m−3, about 1.5 times that of Air . The carbon dioxide molecule (O=C=O) contains two Double Bonds and has a linear shape. It has no electrical Dipole . As it is fully oxidized, it is not very reactive and, in particular, not Flammable . At temperatures below −78 °C, carbon dioxide changes directly from a gas to a white solid called Dry Ice through a process called Deposition . Liquid carbon dioxide forms only at Pressure s above 5.1 Atm ; at atmospheric pressure, it passes directly between the gaseous and solid phases in a process called Sublimation . Water will absorb its own Volume of carbon dioxide, and more than this under pressure. About 1% of the dissolved carbon dioxide turns into Carbonic Acid . The carbonic acid in turn dissociates partly to form Bicarbonate and Carbonate Ion s. Laboratory test for carbon dioxide When a lighted splint is inserted into a test tube containing carbon dioxide, the flame is immediately extinguished, as carbon dioxide does not support combustion (certain Fire Extinguishers contain carbon dioxide to extinguish the flame). Of course if you are genuinely unsure what gas you are testing (hydrogen, natural gas, etc.) igniting with a lighted split may not be a good idea. This method is inconclusive because other gases can extinguish a flame. To further confirm that the gas is carbon dioxide, the gas may be bubbled into Calcium Hydroxide solution ( Lime Water ). The lime water will turn milky if CO2 is introduced because of the formation of Calcium Carbonate . These tests are nowadays confined to schools. In a modern laboratory, Spectroscopic Methods such as Infrared Spectroscopy are employed to detect and confirm the presence of CO2. An example of an application of IR spectroscopy to detect CO2 is the measuring of the atmospheric CO2 concentration to monitor the extent of the Greenhouse Effect . USES Liquid and solid carbon dioxide are important Refrigerant s, especially in the Food Industry , where they are employed during the transportation and storage of Ice Cream and other Frozen Food s. Solid carbon dioxide is called "dry ice" and is used for small shipments where refrigeration equipment is not practical. Carbon dioxide is used to produce Carbonated Soft Drink s and Soda Water . Candy called Pop Rocks is pressurized with carbon dioxide gas at about 600 PSI. When you put the candy in your mouth, it melts (just like other hard candy) and releases the gas bubbles with an audible "pop". Traditionally, the carbonation in Beer and Sparkling Wine comes about through natural fermentation, but some manufacturers carbonate these drinks Artificial ly. The Leavening Agent s used in baking produce carbon dioxide to cause dough to rise. Baker's Yeast produces carbon dioxide by fermentation within the dough, while chemical leaveners such as Baking Powder and Baking Soda release carbon dioxide when heated or exposed to Acid s. Carbon dioxide is often used as an inexpensive, nonflammable pressurized gas. Life Jacket s often contain canisters of pressured carbon dioxide for quick inflation. Steel capsules are also sold as supplies of compressed gas for Airguns , Paintball markers, for inflating Bicycle tires, and for making Seltzer . Rapid vaporization of liquid CO2 is used for blasting in Coal Mine s. Carbon dioxide extinguishes flames, and some Fire Extinguishers , especially those designed for electrical fires, contain liquid carbon dioxide under pressure. Carbon dioxide also finds use as an atmosphere for Welding , although in the welding arc, it reacts to Oxidize most metals. Use in the automotive industry is common despite significant evidence that welds made in carbon dioxide are Brittle r than those made in more inert atmospheres, and that such weld joints deteriorate over time because of the formation of carbonic acid. It is used as a welding gas primarily because it is much less expensive than more inert gases such as Argon or Helium . Liquid carbon dioxide is a good Solvent for many Organic Compounds , and is used to remove Caffeine from Coffee . First, the green Coffee Beans are soaked in water. The beans are placed in the top of a column that's seventy feet high. The carbon dioxide Fluid at about 93 degrees Cel. enters at the bottom of the column. The caffeine diffuses out of the beans and into the carbon dioxide. Carbon dioxide has begun to attract attention in the Pharmaceutical and other chemical processing industries as a less toxic alternative to more traditional solvents such as Organochloride s. It's used by some Dry Cleaners for this reason. (See Green Chemistry .) Plants require carbon dioxide to conduct Photosynthesis , and greenhouses may enrich their atmospheres with additional CO2 to boost plant growth. It has been proposed that carbon dioxide from power generation be bubbled into ponds to grow Algae that could then be converted into Biodiesel fuel {Link without Title} . High levels of carbon dioxide in the atmosphere effectively exterminate many pests. Greenhouses will raise the level of CO2 to 10,000 ppm (1%) for several hours to eliminate pests such as whiteflies, spider mites, and others. In medicine, up to 5% carbon dioxide is added to pure Oxygen for stimulation of breathing after Apnea and to stabilize the O2/CO2 balance in blood. A common type of industrial gas Laser , the Carbon Dioxide Laser , uses carbon dioxide as a medium. Carbon dioxide is commonly injected into or adjacent to producing Oil Well s. It will act as both a pressurizing agent and, when dissolved into the underground Crude Oil , will significantly reduce its viscosity, enabling the oil to flow more rapidly through the earth to the removal well. In mature oil fields, extensive pipe networks are used to carry the carbon dioxide to the injection points. DRY ICE Dry ice is a Genericized Trademark for solid ("frozen") Carbon Dioxide . The term was coined in 1925 by Prest Air Devices, a company formed in Long Island City, New York in 1923.1 Dry ice at normal pressures does not melt into liquid carbon dioxide but rather Sublimates directly into carbon dioxide gas at −78.5 °C (−109.3 °F ). Hence it is called "dry ice" as opposed to normal "wet" Ice (frozen water). Dry ice is produced by compressing carbon dioxide gas to a liquid form, removing the heat produced by the compression (see Charles' Law ), and then letting the liquid carbon dioxide expand quickly. This expansion causes a drop in Temperature so that some of the CO2 freezes into "snow", which is then compressed into pellets or blocks. Uses . ( New York City , New York , U.S. )]]
Handling Because of its particular characteristics, dry ice requires special precautions when handling. It is extremely cold and there should be no direct contact with skin (i.e., wear proper insulating gloves). It is constantly sublimating to carbon dioxide gas, so it cannot be stored in a sealed container as the pressure buildup will quickly cause the container to explode. The sublimated gas must be ventilated; otherwise, it may fill the enclosed space and create a Suffocation hazard. Special care for ventilating vehicles is needed as well because of the small space. People who handle dry ice should also be aware that carbon dioxide is heavier than air and will sink to the floor. Some markets require those purchasing dry ice to be of 18 years of age or older. BIOLOGY Carbon dioxide is an end product in organisms that obtain energy from breaking down Sugar s or Fat s with Oxygen as part of their Metabolism , in a process known as Cellular Respiration . This includes all plants, Animal s, many Fungi and some Bacteria . In higher animals, the carbon dioxide travels in the Blood from the body's tissues to the Lung s where it's exhaled. Carbon dioxide content in fresh Air is approximately 0.04%, and in exhaled air approximately 4.5%. When inhaled in high concentrations (about 5% by volume), it is Toxic to humans and other animals. This is sometimes known as Choke Damp , an old mining industry term, and was the cause of death at Lake Nyos in Cameroon , where an upwelling of CO2-laden lake water in 1986 covered a wide area in a blanket of the gas, killing nearly 2000. Hemoglobin , the main oxygen-carrying molecule in Red Blood Cell s, can carry both oxygen and carbon dioxide, although in quite different ways. The decreased binding to oxygen in the blood due to increased carbon dioxide levels is known as the Haldane Effect , and is important in the transport of carbon dioxide from the tissues to the lungs. Conversely, a rise in the partial pressure of CO2 or a lower pH will cause offloading of oxygen from hemoglobin. This is known as the Bohr Effect . According to a study by the USDA,2 an average person's respiration generates approximately 450 liters (roughly 900 grams) of carbon dioxide per day. CO2 is carried in blood in three different ways. Most of it (about 80%–90%) is converted to bicarbonate ions HCO3− by the enzyme Carbonic Anhydrase in the red blood cells. 5%–10% is dissolved in the plasma and 5%–10% is bound to hemoglobin as carbamino compounds. The exact percentages vary depending whether it is arterial or venous blood. The CO2 bound to hemoglobin does not bind to the same site as oxygen; rather it combines with the N-terminal groups on the four globin chains. However, because of Allosteric effects on the hemoglobin molecule, the binding of CO2 does decrease the amount of oxygen that is bound for a given partial pressure of oxygen. Carbon dioxide may be one of the mediators of local autoregulation of blood supply. If it is high, the Capillaries expand to allow a greater blood flow to that tissue. Bicarbonate ions are crucial for regulating blood pH. As breathing rate influences the level of CO2 in blood, too slow or shallow breathing causes Respiratory Acidosis , while too rapid breathing, Hyperventilation , leads to Respiratory Alkalosis . It is interesting to note that although it is oxygen that the body requires for metabolism, it is not low oxygen levels that stimulate breathing, but is instead higher carbon dioxide levels. As a result, breathing low-pressure air or a gas mixture with no oxygen at all (e.g., pure nitrogen) leads to loss of consciousness without subjective breathing problems. This is especially perilous for high-altitude fighter pilots, and is also the reason why the instructions in commercial airplanes for case of loss of cabin pressure stress that one should apply the Oxygen Mask to oneself before helping others—otherwise one risks going unconscious without being aware of the imminent peril. Plants remove carbon dioxide from the atmosphere by Photosynthesis , which uses light energy to produce organic plant materials by combining carbon dioxide and Water . This releases free oxygen gas. Sometimes carbon dioxide gas is pumped into Greenhouse s to promote plant growth. Plants also emit CO2 during respiration, but on balance they are net sinks of CO2. OSHA limits carbon dioxide concentration in the workplace to 0.5% for prolonged periods. The U.S. National Institute for Occupational Safey and Health limits brief exposures (up to ten minutes) to 3% and considers concentrations exceeding 4% as " Immediately Dangerous To Life And Health ." People who breathe 5% carbon dioxide for more than half an hour show signs of acute Hypercapnia , while breathing 7%–10% carbon dioxide can produce unconsciousness in only a few minutes. Carbon dioxide, either as a gas or as dry ice, should be handled only in well-ventilated areas See Also: Arterial blood gas CAPTURING/EXTRACTING CO<SUB>2</SUB> Methods of CO2 extraction/separation include: www.netl.doe.gov (pdf file)
Calcium Oxide Carbon Dioxide reacts with Quicklime (calcium oxide), to form Limestone (calcium carbonate). {Link without Title} Serpentine The metamorphic mineral serpentine(magnesium silicate hydroxide), is composed of magnesium, silicon and oxygen. Ovivine {Link without Title} {Link without Title}
The RCRS on the space shuttle Orbiter uses a two-bed system that provides continuous removal of CO2 without expendable products. Regenerable systems allow a shuttle mission a longer stay in space without having to replenish its sorbent canisters. Older Lithium Hydroxide (LiOH)-based systems, which are non-regenerable, are being replaced by regenerable Metal-oxide -based systems. A metal-oxide-based system primarily consists of a metal oxide sorbent canister and a regenerator assembly. This system works by removing carbon dioxide using a Sorbent material and then regenerating the Sorbent material. The metal-oxide sorbent is regenerated by pumping air heated to around 400º F at 7.5 scfm through its canister for 10 hours. {Link without Title} OCEANS The Earth's Ocean s contain a huge amount of carbon dioxide in the form of bicarbonate and carbonate ions—much more than the amount in the atmosphere. The bicarbonate is produced in reactions between rock, water, and carbon dioxide. One example is the dissolution of calcium carbonate: :CaCO3 + CO2 + H2O Ca2+ + 2 HCO3- Reactions like this tend to buffer changes in atmospheric CO2. Reactions between carbon dioxide and non-carbonate rocks also add bicarbonate to the seas, which can later undergo the reverse of the above reaction to form carbonate rocks, releasing half of the bicarbonate as CO2. Over hundreds of millions of years this has produced huge quantities of carbonate rocks. If all the carbonate rocks in the earth's crust were to be converted back into carbon dioxide, the resulting carbon dioxide would weigh 40 times as much as the rest of the atmosphere. The vast majority of CO2 added to the atmosphere will eventually be absorbed by the oceans and become bicarbonate ion, but the process takes on the order of a hundred years because most seawater rarely comes near the surface. HISTORY Carbon dioxide was one of the first gases to be described as a substance distinct from air. In the 17th Century , the Flemish chemist Jan Baptist Van Helmont observed that when he burned Charcoal in a closed vessel, the mass of the resulting ash was much less than that of the original charcoal. His interpretation was that the rest of the charcoal had been Transmuted into an invisible substance he termed a "gas" or "wild spirit" (''spiritus sylvestre''). Carbon dioxide's properties were studied more thoroughly in the 1750s by the Scottish physician Joseph Black . He found that Limestone ( Calcium Carbonate ) could be heated or treated with Acid s to yield a gas he termed "fixed air." He observed that the fixed air was denser than air and did not support either flame or animal life. He also found that it would, when bubbled through an aqueous solution of lime ( Calcium Hydroxide ), precipitate calcium carbonate, and used this phenomenon to illustrate that carbon dioxide is produced by animal respiration and microbial fermentation. In 1772 , Joseph Priestley used carbon dioxide produced from the action of sulfuric acid on limestone to prepare soda water, the first known instance of an artificially carbonated drink. Carbon dioxide was first liquefied (at elevated pressures) in 1823 by Humphrey Davy and Michael Faraday . The earliest description of solid carbon dioxide was given by Charles Thilorier , who in 1834 opened a pressurized container of liquid carbon dioxide, only to find that the cooling produced by the rapid evaporation of the liquid yielded a "snow" of solid CO2. SEE ALSO REFERENCES EXTERNAL LINKS
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