Dictionary
a colorless gas (O3) soluble in alkalis and cold water a strong oxidizing agent can be produced by electric discharge in oxygen or by the action of ultraviolet radiation on oxygen in the stratosphere (where it acts as a screen for ultraviolet radiation)
|
Wikipedia
Ozone (O 3) is an allotrope of oxygen, the molecule consisting of three oxygen atoms instead of the more stable diatomic !O 2.Ozon e? is a colorless gas at standard temperature and pressure. It forms a dark blue liquid below -112 °C and a dark blue solid below -193 °C. Ozone is a powerful oxidizing agent. It is also unstable, decaying to ordinary oxygen through the !reaction:2O 3? → 3O2. This reaction proceeds more rapidly with increasing temperature and increasing pressure.Ozone is a highly corrosive, poisonous substance and a common pollutant. It has a sharp, pungent odor. It is present in low concentrations throughout the Earth's atmosphere. It is also formed from O2 by electrical discharges such as lightning, and by action of high energy electromagnetic radiation.Some kinds of electrical equipment generate levels of ozone that a human can easily smell. This is especially true of devices using High-voltage hazardshigh voltages, such as television sets and photocopiers. Electric motors using brush (electric)brushes can generate ozone from repeated spark gapsparking inside the unit. Large motors, such as those used by elevators or hydraulic pumps, will generate more ozone than smaller motors.
Ozone layer - ''See main article: Ozone layer.''The highest levels of ozone in the atmosphere are in the stratosphere, in a region also known as the ozone layer. Here it filters out much ultraviolet light from the Sun that would be harmful to most forms of life. The standard way to express total ozone amounts in the atmosphere is by using Dobson units. Ozone used in industry is measured in Parts per millionppm (OSHA exposure limits for example), and percent by mass or weight.
Discovery of ozone - Ozone was discovered by Christian Friedrich Schönbein in 1840, who "noted ozone appeared during thunderstorms and named the gas ozone for its peculiar smell (ozo is Greek for smell)." todayinsci.com. "The word ozone comes from the Greek word ozein meaning "smell", but the strong odor associated with ozone (what you'd smell after a lightning strike) is not from the ozone, but rather from the ionization (freeing of electrons) that takes place during ozone formation and destruction." ? gcmd.gsfc.nasa.gov.
Industrial production - Industrially, ozone is produced with short wavelength ultraviolet radiation from a mercury_vapormercury vapor lamp or the application of a high voltage electrical field in a process called ''cold discharge''. The cold discharge apparatus consists of two metal plates separated by an air gap and a high dielectric strength electrical insulator such as borosilicate glass or mica. A high voltage alternating current is applied to the plates and the ozone is formed in the air gap when O2 molecules disassociate and recombine into O3. A faint Corona_dischargecorona may be present in the air gap, but the voltage is maintained below that which would cause punch-through of the insulator with subsequent arcing and plasma formation. In the laboratory ozone can be produced by electrolysis using a 9 Volt battery, a pencil graphite rod cathode, a platinum wire anode and a 3M sulfuric acid electrolyte Ref1 . The half cell reactions taking place !are::3H23 + 6H+ + 6e- Table of standard electrode potentials!δEoV:6H+ + 6e- → 3H2 Table of standard electrode potentials!δEoV:2H2O → O2 + 4H+ + 4H- Table of standard electrode potentials!δEoVSo that in the net reaction three equivalents of water are converted into one equivalent of ozone and one equivalent of hydrogen. Oxygen formation is a competing reaction.
Use in industry - Ozone can be used for Bleach (chemical)bleaching substances and for killing bacteria. Many municipal drinking water systems kill bacteria with ozone instead of the more common chlorine. Ozone does not form organochlorine compounds, but it also does not remain in the water after treatment, so some systems introduce a small amount of chlorine to prevent bacterial growth in the pipes, or may use chlorine intermittently, based on results of periodic testing. Where electrical power is abundant, ozone is a cost-effective method of treating water, as it is produced on demand and does not require transportation and storage of hazardous chemicals. Once it has decayed, it leaves no taste or odor in drinking water.Industrially, ozone or ozonated water is used to: disinfect water before it is bottled, kill bacteria on food-contact surfaces scrub yeast and mold spores from the air in food processing plants wash fresh fruits and vegetables to kill yeast, mold and bacteria chemically attack contaminants in water (iron, arsenic, hydrogen sulfide, nitrites, and complex organics lumped together as "color"), provide an aid to flocculation (a process of agglomeration of molecules, which aids in filtration... this is where the iron and arsenic are removed), clean and bleach fabrics (the latter use is patented), assist in processing plastics to allow adhesion of inks, age rubber samples to determine the useful life of a batch of rubber.Ozone is a reagent in many organic reactions in the laboratory and in industry. Ozonolysis is the cleavage of an alkene to carbonyl compounds.
Use in medicine - Ozone, along with hypochlorite ions, is naturally produced by white blood cells and the roots of marigolds as a means of destroying foreign bodies. When ozone breaks down it gives rise to oxygen free radicals, which are highly reactive and damage or destroy most organic molecules. Ozone has a number of medical uses. It can be used to affect the body's antioxidant-prooxidant balance, since the body usually reacts to its presence by producing antioxidant enzymes.
Air Pollution - Ozone at the earth's surface is considered a pollutent, although ozone is not emitted by car engines or by industial operations. Cars and industrials sources emit hydrocarbons that reacts oxygen in sunlight to form ozone. Ozone reacts with nitrogen oxide (NO) to form nitrogen dioxide (NO2). This reduces levels of nitrogen oxide in the air. Nitrogen oxide in the human body dialates arteries. This lower level of nitrogen oxide in the atmophere make it more difficult for persons with impared heart or lung function to breath. Ozone also damages lung tissue by its powerful oxidizing action. Ozone therapy has blossomed into a thriving field of alternative medicine, and there are a host of claimed applications above and beyond what has actually been verified by studies. Ozone treatments are dangerous, however, since ozone is highly corrosive.In the USA ozone therapy is illegal, as the FDA has not approved its use on humans. At least one death has been attributed to application of ozone through Wiktionary:insufflationinsufflation in the USA. "Air cleaners" which produce "activated oxygen", i.e. ozone, are often sold in the US nonetheless. See Air ioniser.Ozone has been found to convert cholesterol in the blood stream to plaque (which causes hardening and narrowing of arteries). This cholesterol product has also been implicated in Alzheimer's disease, suggesting a link between the inflammatory response associated with head injury and Alzheimer's.Ozone has been studied extensively, and found to be Carcinogencarcinogenic to some animals (and not others), and a Mutagenmutagen to some bacteria.
See also - Ozone depletion, including the phenomenon known as the ''Ozone Hole''. Ozone layer Tropospheric ozone
External links - earthobservatory.nasa.gov - NASA's Earth Observatory article on Ozoneinternet12.eapps.com - International Day for the Preservation of the Ozone Layerilo.org - International Chemical Safety Card 0068cdc.gov - NIOSH Pocket Guide to Chemical HazardsWHO-Europe reports: who.dk - Health Aspects of Air Pollution (2003) (PDF) and "euro.who.int - Answer to follow-up questions from CAFE (2004) (PDF)greenfacts.org - Ground-level Ozone Air Pollution — A summary for non specialists by GreenFacts of the above WHO reports.
References - Note1 ''Laboratory Experiments on the Electrochemical Remediation of the Environment. Part 7: Microscale Production of Ozone '' Jorge G. Ibanez, Rodrigo Mayen-Mondragon, and M. T. Moran-Moran J. Chem. Ed. October 2005 Vol. 82 No. 10 p. 1546 jchemed.chem.wisc.edu - Abstract Category:Environmental chemistryCategory:Oxygen compoundsCategory:Ozone !depletionCategory:AntisepticsC ategory:reagents? for organic !chemistrybg:Озонca:Ozócs: Ozónda:Ozonde:Ozonet:Osoones: Ozonoeo:Ozonofr:Ozonegl:Ozonok o:오존hr:Ozonis:Ósonit:Ozon ohe:אוזוןhu:Ózonms:Ozonn l:Ozonja:オゾンno:Ozonnn:Oz onoc:Ozònepl:Ozon? !(chemia)pt:Ozônioru:Озонs k:Ozónsr:Озонfi:Otsonivi: Ôzôntr:Ozonzh:臭氧?
|
|
|