Oxygen:the element with atomic number 8

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from theGreek roots ???? (oxys) ("acid", literally "sharp", referring to the sour taste of acids) and -????? (-gen?s) ("producer", literally "begetter"), because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition. Sony VAIO VPC-P114KX/G Battery

At standard temperature and pressure, two atoms of the element bind to form dioxygen, a very pale blue, odorless, tasteless diatomic gas with the formula O2.

Oxygen is a member of the chalcogen group on the periodic table and is a highly reactive nonmetallic element that readily forms compounds (notably oxides) with almost all other elements. Sony VAIO VPC-P114KX/P Battery

Oxygen is a strong oxidizing agent and has the second highest electronegativity of all the elements (only fluorine has a higher electronegativity).[1] By mass, oxygen is the third most abundant element in the universe after hydrogen and helium[2] and the most abundant element by mass in the Earth's crust, making up almost half of the crust's mass.Sony VAIO VPC-P114KX/W Battery

Free oxygen is too chemically reactive to appear on Earth without thephotosynthetic action of living organisms, which use the energy of sunlight to produce elemental oxygen from water. ElementalO2 only began to accumulate in the atmosphere after the evolutionary appearance of these organisms, roughly 2.5 billion years ago.Sony VAIO VPCP115JC Battery

Diatomic oxygen gas constitutes 20.8% of the volume of air.

Because it comprises most of the mass in water, oxygen comprises most of the mass of living organisms (for example, about two-thirds of the human body's mass).Sony VAIO VPCP115JC/B Battery

All major classes of structural molecules in living organisms, such as proteins,carbohydrates, and fats, contain oxygen, as do the major inorganic compounds that comprise animal shells, teeth, and bone. Elemental oxygen is produced by cyanobacteria, algae and plants, and is used in cellular respiration for all complex life.Sony VAIO VPCP115JC/D Battery

Oxygen is toxic to obligately anaerobic organisms, which were the dominant form of early life on Earth until O2 began to accumulate in the atmosphere. Another form (allotrope) of oxygen, ozone (O3), helps protect the biosphere from ultraviolet radiation with the high-altitude ozone layer, but is a pollutant near the surface where it is a by-product of smog.Sony VAIO VPCP115JC/G Battery

At even higher low earth orbit altitudes atomic oxygen is a significant presence and a cause of erosion for spacecraft.

Oxygen was independently discovered by Carl Wilhelm Scheele, in Uppsala, in 1773 or earlier, and Joseph Priestley inWiltshire, in 1774, but Priestley is often given priority because his work was published first. Sony VAIO VPCP115JC/P Battery

The name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory ofcombustion and corrosion.

Oxygen is produced industrially by fractional distillation of liquefied air, use of zeolites with pressure-cycling to concentrate oxygen from air, electrolysis of water and other means. Sony VAIO VPCP115JC/W Battery

Uses of oxygen include the production of steel, plastics and textiles; rocket propellant; oxygen therapy; and life support in aircraft, submarines, spaceflight and diving.

Structure

At standard temperature and pressure, oxygen is a very pale blue, odorless gas with the molecular formula O2, in which the two oxygen atoms are chemically bonded to each other with a spin tripletelectron configuration. Sony VAIO VPCP115KG Battery

This bond has a bond order of two, and is often simplified in description as a double bond or as a combination of one two-electron bond and two three-electron bonds.

Triplet oxygen (not to be confused with ozone, O3) is the ground state of the O2 molecule.The electron configuration of the molecule has two unpaired electrons occupying two degeneratemolecular orbitals.Sony VAIO VPCP116KG Battery

These orbitals are classified as antibonding (weakening the bond order from three to two), so the diatomic oxygen bond is weaker than the diatomic nitrogen triple bond in which all bonding molecular orbitals are filled, but some antibonding orbitals are not.

In normal triplet form, O2 molecules are paramagnetic. Sony VAIO VPC-P116KX/B Battery

That is, they form a magnet in the presence of a magnetic field—because of the spin magnetic moments of the unpaired electrons in the molecule, and the negative exchange energy between neighboring O2 molecules. Liquid oxygen is attracted to a magnet to a sufficient extent that, in laboratory demonstrations, a bridge of liquid oxygen may be supported against its own weight between the poles of a powerful magnet.Sony VAIO VPC-P116KX/D Battery

Singlet oxygen is a name given to several higher-energy species of molecular O2 in which all the electron spins are paired. It is much more reactive towards common organic molecules than is molecular oxygen per se. In nature, singlet oxygen is commonly formed from water during photosynthesis, using the energy of sunlight.Sony VAIO VPC-P116KX/G Battery

It is also produced in the troposphere by the photolysis of ozone by light of short wavelength,and by the immune system as a source of active oxygen. Carotenoids in photosynthetic organisms (and possibly also in animals) play a major role in absorbing energy from singlet oxygen and converting it to the unexcited ground state before it can cause harm to tissues.Sony VAIO VPC-P116KX/P Battery

Allotropes

The common allotrope of elemental oxygen on Earth is called dioxygen, O2. It has a bond length of 121 pm and a bond energy of 498 kJ·mol?1. This is the form that is used by complex forms of life, such as animals, in cellular respiration (seeBiological role) and is the form that is a major part of the Earth's atmosphere (see Occurrence). Sony VAIO VPC-P116KX/W Battery

Other aspects of O2 are covered in the remainder of this article.

Trioxygen (O3) is usually known as ozone and is a very reactive allotrope of oxygen that is damaging to lung tissue. Ozone is produced in the upper atmosphere when O2 combines with atomic oxygen made by the splitting of O2 by ultraviolet (UV) radiation.Sony VAIO VPCP118JC Battery

Since ozone absorbs strongly in the UV region of the spectrum, the ozone layer of the upper atmosphere functions as a protective radiation shield for the planet.[7] Near the Earth's surface, however, it is a pollutant formed as a by-product of automobile exhaust.Sony VAIO VPCP118JC/B Battery

The metastable molecule tetraoxygen (O4) was discovered in 2001, and was assumed to exist in one of the six phases of solid oxygen. It was proven in 2006 that this phase, created by pressurizing O2 to 20 GPa, is in fact a rhombohedralO8 cluster. This cluster has the potential to be a much more powerful oxidizer than either O2 or O3 and may therefore be used inrocket fuel.Sony VAIO VPCP118JC/P Battery

A metallic phase was discovered in 1990 when solid oxygen is subjected to a pressure of above 96 GPa and it was shown in 1998 that at very low temperatures, this phase becomes superconducting.

Physical properties

Oxygen is more soluble in water than nitrogen is; water contains approximately 1 molecule of O2 for every 2 molecules of N2, compared to an atmospheric ratio of approximately 1:4.Sony VAIO VPCP118JC/W Battery

The solubility of oxygen in water is temperature-dependent, and about twice as much (14.6 mg·L?1) dissolves at 0 °C than at 20 °C (7.6 mg·L?1).At 25 °C and 1 standard atmosphere (101.3 kPa) of air, freshwater contains about 6.04 milliliters (mL) of oxygen per liter, whereas seawater contains about 4.95 mL per liter.Sony VAIO VPC-P118KX/B Battery

At 5 °C the solubility increases to 9.0 mL (50% more than at 25 °C) per liter for water and 7.2 mL (45% more) per liter for sea water.

Oxygen condenses at 90.20 K (?182.95 °C, ?297.31 °F), and freezes at 54.36 K (?218.79 °C, ?361.82 °F). Both liquid and solid O2are clear substances with a light sky-blue color caused by absorption in the red (in contrast with the blue color of the sky, which is due to Rayleigh scattering of blue light). Sony VAIO VPC-P118KX/D Battery

High-purity liquid O2 is usually obtained by the fractional distillation of liquefied air.[30]Liquid oxygen may also be produced by condensation out of air, using liquid nitrogen as a coolant. It is a highly reactive substance and must be segregated from combustible materials.Sony VAIO VPC-P118KX/G Battery

Isotopes and stellar origin

Naturally occurring oxygen is composed of three stable isotopes, 16O, 17O, and 18O, with 16O being the most abundant (99.762% natural abundance).

Most 16O is synthesized at the end of the helium fusion process in massive stars but some is made in the neon burning process.Sony VAIO VPC-P118KX/P Battery

17O is primarily made by the burning of hydrogen into helium during the CNO cycle, making it a common isotope in the hydrogen burning zones of stars.[33] Most 18O is produced when 14N (made abundant from CNO burning) captures a 4He nucleus, making 18O common in the helium-rich zones of evolved, massive stars.Sony VAIO VPC-P118KX/W Battery

Fourteen radioisotopes have been characterized, the most stable are 15O with a half-life of 122.24 seconds and 14O with a half-life of 70.606 seconds. All of the remaining radioactive isotopes have half-lives that are less than 27 s and the majority of these have half-lives that are less than 83 milliseconds.Sony VAIO VPCP119JC Battery

The most common decay mode of the isotopes lighter than 16O is ?+ decay to yield nitrogen, and the most common mode for the isotopes heavier than 18O is beta decay to yield fluorine.

Occurrence

Oxygen is the most abundant chemical element, by mass, in our biosphere, air, sea and land. Oxygen is the third most abundant chemical element in the universe, after hydrogen and helium.Sony VAIO VPCP119JC/BI Battery

About 0.9% of the Sun's mass is oxygen.[5] Oxygen constitutes 49.2% of the Earth's crust by mass and is the major component of the world's oceans (88.8% by mass).[5] Oxygen gas is the second most common component of the Earth's atmosphere, taking up 21.0% of its volume and 23.1% of its mass (some 1015tonnes).Sony VAIO VPCP11S1E/B Battery

Earth is unusual among the planets of the Solar System in having such a high concentration of oxygen gas in its atmosphere: Mars (with 0.1% O2 by volume) and Venus have far lower concentrations. However, the O2 surrounding these other planets is produced solely by ultraviolet radiation impacting oxygen-containing molecules such as carbon dioxide.Sony VAIO VPC-P11S1E/B Battery

The unusually high concentration of oxygen gas on Earth is the result of the oxygen cycle. This biogeochemical cycle describes the movement of oxygen within and between its three main reservoirs on Earth: the atmosphere, the biosphere, and the lithosphere. The main driving factor of the oxygen cycle is photosynthesis, which is responsible for modern Earth's atmosphere.Sony VAIO VPCP11S1E/D Battery

Photosynthesis releases oxygen into the atmosphere, while respiration and decay remove it from the atmosphere. In the present equilibrium, production and consumption occur at the same rate of roughly 1/2000th of the entire atmospheric oxygen per year.Sony VAIO VPC-P11S1E/D Battery

Free oxygen also occurs in solution in the world's water bodies. The increased solubility of O2 at lower temperatures (seePhysical properties) has important implications for ocean life, as polar oceans support a much higher density of life due to their higher oxygen content.Sony VAIO VPCP11S1E/G Battery

Polluted water may have reduced amounts of O2 in it, depleted by decaying algae and other biomaterials through a process called eutrophication. Scientists assess this aspect of water quality by measuring the water's biochemical oxygen demand, or the amount of O2 needed to restore it to a normal concentration.Sony VAIO VPC-P11S1E/G Battery

Photosynthesis and respiration

In nature, free oxygen is produced by the light-driven splitting of water during oxygenic photosynthesis. According to some estimates, Green algae and cyanobacteria in marine environments provide about 70% of the free oxygen produced on earth and the rest is produced by terrestrial plants.Sony VAIO VPCP11S1E/P Battery

Other estimates of the oceanic contribution to atmospheric oxygen are higher, while some estimates are lower, suggesting oceans produce ~45% of Earth's atmospheric oxygen each year.

A simplified overall formula for photosynthesis is:

6 CO2 + 6 H2O + photons ? C6H12O6 + 6 O2 (or simply carbon dioxide + water + sunlight ? glucose + dioxygen)Sony VAIO VPCP11S1E/W Battery

Photolytic oxygen evolution occurs in the thylakoid membranes of photosynthetic organisms and requires the energy of fourphotons.Many steps are involved, but the result is the formation of a proton gradient across the thylakoid membrane, which is used to synthesize ATP via photophosphorylation.Sony VAIO VPC-P11S1E/W Battery

The O2 remaining after oxidation of the water molecule is released into the atmosphere.

Molecular dioxygen, O2, is essential for cellular respiration in all aerobic organisms. Oxygen is used in mitochondria to help generate adenosine triphosphate (ATP) during oxidative phosphorylation. The reaction for aerobic respiration is essentially the reverse of photosynthesis and is simplified as:Sony VAIO VPCP11Z9E/B Battery

C6H12O6 + 6 O2 ? 6 CO2 + 6 H2O + 2880 kJ·mol?1

In vertebrates, O2 is diffused through membranes in the lungs and into red blood cells. Hemoglobin binds O2, changing its color from bluish red to bright red (CO2 is released from another part of hemoglobin through the Bohr effect).Sony VAIO VPCS111FM/S Battery

Other animals usehemocyanin (molluscs and some arthropods) or hemerythrin (spiders and lobsters). A liter of blood can dissolve 200 cm3 ofO2.

Reactive oxygen species, such as superoxide ion (O?2) and hydrogen peroxide (H2O2), are dangerous by-products of oxygen use in organisms.Sony VAIO VPCS115EC Battery

Parts of the immune system of higher organisms, however, create peroxide, superoxide, and singlet oxygen to destroy invading microbes. Reactive oxygen species also play an important role in the hypersensitive response of plants against pathogen attack.

An adult human in rest inhales 1.8 to 2.4 grams of oxygen per minute.Sony VAIO VPCS115FG Battery

This amounts to more than 6 billion tonnes of oxygen inhaled by humanity per year.

Build-up in the atmosphere

Free oxygen gas was almost nonexistent in Earth's atmosphere before photosynthetic archaea and bacteria evolved. Free oxygen first appeared in significant quantities during the Paleoproterozoic eon (between 2.5 and 1.6 billion years ago).Sony VAIO VPCS117GG Battery

At first, the oxygen combined with dissolved iron in the oceans to form banded iron formations. Free oxygen started to outgas from the oceans 2.7 billion years ago, reaching 10% of its present level around 1.7 billion years ago.

The presence of large amounts of dissolved and free oxygen in the oceans and atmosphere may have driven most of theanaerobic organisms then living to extinction during the Great Oxygenation Event(oxygen catastrophe) about 2.4 billion years ago.Sony VAIO VPCS117GGB Battery

However, cellular respiration using O2 enables aerobic organisms to produce much more ATP than anaerobic organisms, helping the former to dominate Earth's biosphere. Photosynthesis and cellular respiration of O2 allowed for the evolution of eukaryotic cells and ultimately complex multicellular organisms such as plants and animals.Sony VAIO VPCS118EC Battery

Since the beginning of the Cambrian period 540 million years ago, O2 levels have fluctuated between 15% and 30% by volume.Towards the end of the Carboniferous period (about 300 million years ago) atmospheric O2 levels reached a maximum of 35% by volume,[51] which may have contributed to the large size of insects and amphibians at this time.Sony VAIO VPCS119FJ/B Battery

Human activities, including the burning of 7 billion tonnes of fossil fuels each year have had very little effect on the amount of free oxygen in the atmosphere. At the current rate of photosynthesis it would take about 2,000 years to regenerate the entire O2 in the present atmosphere.Sony VAIO VPCS119GC Battery

Early experiments

One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle and surrounding the vessel's neck with water resulted in some water rising into the neck.Sony VAIO VPCS11AFJ Battery

Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philo's work by observing that a portion of air is consumed during combustion and respiration.Sony VAIO VPCS11AGJ Battery

In the late 17th century, Robert Boyle proved that air is necessary for combustion. English chemist John Mayow refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus or just nitroaereus. Sony VAIO VPCS11AHJ Battery

In one experiment he found that placing either a mouse or a lit candle in a closed container over water caused the water to rise and replace one-fourteenth of the air's volume before extinguishing the subjects. From this he surmised that nitroaereus is consumed in both respiration and combustion.Sony VAIO VPCS11AVJ Battery

Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. He also thought that the lungs separate nitroaereus from air and pass it into the blood and that animal heat and muscle movement result from the reaction of nitroaereus with certain substances in the body.Sony VAIO VPCS11J7E/B Battery

Accounts of these and other experiments and ideas were published in 1668 in his workTractatus duo in the tract "De respiratione".

Phlogiston theory

Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as an element.Sony VAIO VPCS11M1E/W Battery

This may have been in part due to the prevalence of the philosophy ofcombustion and corrosion called the phlogiston theory, which was then the favored explanation of those processes.

Established in 1667 by the German alchemist J. J. Becher, and modified by the chemist Georg Ernst Stahl by 1731, phlogiston theory stated that all combustible materials were made of two parts. Sony VAIO VPCS11V9E/B Battery

One part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx.

Highly combustible materials that leave little residue, such as wood or coal, were thought to be made mostly of phlogiston;Sony VAIO VPCS11X9E/B Battery

whereas non-combustible substances that corrode, such as iron, contained very little. Air did not play a role in phlogiston theory, nor were any initial quantitative experiments conducted to test the idea; instead, it was based on observations of what happens when something burns, that most common objects appear to become lighter and seem to lose something in the process.Sony VAIO VPCS123FGB Battery

The fact that a substance like wood actually gains overall weight in burning was hidden by the buoyancy of the gaseous combustion products. Indeed one of the first clues that the phlogiston theory was incorrect was that metals, too, gain weight in rusting (when they were supposedly losing phlogiston).Sony VAIO VPCS125EC Battery

Discovery

Oxygen was first discovered by Swedish pharmacist Carl Wilhelm Scheele. He had produced oxygen gas by heating mercuric oxide and various nitrates by about 1772. Scheele called the gas "fire air" because it was the only known supporter of combustion, and wrote an account of this discovery in a manuscript he titled Treatise on Air and Fire, which he sent to his publisher in 1775.Sony VAIO VPCS128EC Battery

However, that document was not published until 1777.

In the meantime, on August 1, 1774, an experiment conducted by the British clergyman Joseph Priestley focused sunlight on mercuric oxide (HgO) inside a glass tube, which liberated a gas he named "dephlogisticated air".Sony VAIO VPCS129GC Battery

He noted that candles burned brighter in the gas and that a mouse was more active and lived longer while breathing it. After breathing the gas himself, he wrote: "The feeling of it to my lungs was not sensibly different from that of common air, but I fancied that my breast felt peculiarly light and easy for some time afterwards."Sony VAIO VPCS12C7E/B Battery

Priestley published his findings in 1775 in a paper titled "An Account of Further Discoveries in Air" which was included in the second volume of his book titled Experiments and Observations on Different Kinds of Air. Because he published his findings first, Priestley is usually given priority in the discovery.Sony VAIO VPCS12L9E/B Battery

The noted French chemist Antoine Laurent Lavoisier later claimed to have discovered the new substance independently. However, Priestley visited Lavoisier in October 1774 and told him about his experiment and how he liberated the new gas. Sony VAIO VPCS12V9E/B Battery

Scheele also posted a letter to Lavoisier on September 30, 1774 that described his own discovery of the previously unknown substance, but Lavoisier never acknowledged receiving it (a copy of the letter was found in Scheele's belongings after his death). Sony VAIO VPCW111XX/P Battery

Lavoisier's contribution

What Lavoisier did indisputably do (although this was disputed at the time) was to conduct the first adequate quantitative experiments onoxidation and give the first correct explanation of how combustion works.Sony VAIO VPCW111XX/PC Battery

He used these and similar experiments, all started in 1774, to discredit the phlogiston theory and to prove that the substance discovered by Priestley and Scheele was a chemical element.

In one experiment, Lavoisier observed that there was no overall increase in weight when tin and air were heated in a closed container.Sony VAIO VPCW111XX/T Battery

He noted that air rushed in when he opened the container, which indicated that part of the trapped air had been consumed. He also noted that the tin had increased in weight and that increase was the same as the weight of the air that rushed back in. This and other experiments on combustion were documented in his book Sur la combustion en général, which was published in 1777.Sony VAIO VPCW111XX/W Battery

In that work, he proved that air is a mixture of two gases; 'vital air', which is essential to combustion and respiration, and azote(Gk. ??????"lifeless"), which did not support either. Azote later became nitrogen in English, although it has kept the name in French and several other European languages.Sony VAIO VPCW111XXP Battery

Lavoisier renamed 'vital air' to oxygène in 1777 from the Greek roots ???? (oxys) (acid, literally "sharp," from the taste of acids) and-????? (-gen?s) (producer, literally begetter), because he mistakenly believed that oxygen was a constituent of all acids. Chemists (notably Sir Humphrey Davy in 1812) eventually determined that Lavoisier was wrong in this regard (it is in fact hydrogen that forms the basis for acid chemistry), but by that time it was too late, the name had taken.Sony VAIO VPCW111XXT Battery

Oxygen entered the English language despite opposition by English scientists and the fact that the Englishman Priestley had first isolated the gas and written about it. This is partly due to a poem praising the gas titled "Oxygen" in the popular book The Botanic Garden (1791) by Erasmus Darwin, grandfather of Charles Darwin.Sony VAIO VPCW111XXW Battery

Later history

John Dalton's original atomic hypothesis assumed that all elements were monoatomic and that the atoms in compounds would normally have the simplest atomic ratios with respect to one another. For example, Dalton assumed that water's formula was HO, giving theatomic mass of oxygen as 8 times that of hydrogen, instead of the modern value of about 16.Sony VAIO VPCW115XG Battery

In 1805, Joseph Louis Gay-Lussacand Alexander von Humboldt showed that water is formed of two volumes of hydrogen and one volume of oxygen; and by 1811 Amedeo Avogadro had arrived at the correct interpretation of water's composition, based on what is now called Avogadro's law and the assumption of diatomic elemental molecules.Sony VAIO VPCW115XGP Battery

By the late 19th century scientists realized that air could be liquefied, and its components isolated, by compressing and cooling it. Using a cascade method, Swiss chemist and physicist Raoul Pierre Pictet evaporated liquid sulfur dioxide in order to liquefy carbon dioxide, which in turn was evaporated to cool oxygen gas enough to liquefy it.Sony VAIO VPCW115XW/P Battery

He sent a telegram on December 22, 1877 to the French Academy of Sciences in Paris announcing his discovery of liquid oxygen.Just two days later, French physicist Louis Paul Cailletet announced his own method of liquefying molecular oxygen. Only a few drops of the liquid were produced in either case so no meaningful analysis could be conducted. Sony VAIO VPCW115XW/T Battery

Oxygen was liquified in stable state for the first time on March 29, 1883 by Polish scientists from Jagiellonian University, Zygmunt Wróblewski and Karol Olszewski.

In 1891 Scottish chemist James Dewar was able to produce enough liquid oxygen to study. Sony VAIO VPCW115XW/W Battery

The first commercially viable process for producing liquid oxygen was independently developed in 1895 by German engineer Carl von Linde and British engineer William Hampson. Both men lowered the temperature of air until it liquefied and then distilled the component gases by boiling them off one at a time and capturing them.Sony VAIO VPCW117XC/P Battery

Later, in 1901, oxyacetylene welding was demonstrated for the first time by burning a mixture ofacetylene and compressed O2. This method of welding and cutting metal later became common.

In 1898, physicist Lord Kelvin calculated that only 400-500 years of oxygen remained on the planet, based on the rate of use of fossil fuels for combustion. Sony VAIO VPCW117XC/T Battery

In 1923 the American scientist Robert H. Goddard became the first person to develop a rocket engine; the engine used gasoline for fuel and liquid oxygen as theoxidizer. Goddard successfully flew a small liquid-fueled rocket 56 m at 97 km/h on March 16, 1926 in Auburn, Massachusetts, USA.Sony VAIO VPCW117XC/W Battery

Industrial production

Two major methods are employed to produce 100 million tonnes of O2 extracted from air for industrial uses annually. The most common method is to fractionally distill liquefied air into its various components, with N2 distilling as a vapor while O2 is left as a liquid.Sony VAIO VPCW119XJ Battery

The other major method of producing O2 gas involves passing a stream of clean, dry air through one bed of a pair of identicalzeolite molecular sieves, which absorbs the nitrogen and delivers a gas stream that is 90% to 93% O2. Simultaneously, nitrogen gas is released from the other nitrogen-saturated zeolite bed, Sony VAIO VPCW119XJ/P Battery

by reducing the chamber operating pressure and diverting part of the oxygen gas from the producer bed through it, in the reverse direction of flow. After a set cycle time the operation of the two beds is interchanged, thereby allowing for a continuous supply of gaseous oxygen to be pumped through a pipeline. This is known aspressure swing adsorption. Sony VAIO VPCW119XJ/W Battery

Oxygen gas is increasingly obtained by these non-cryogenic technologies (see also the related vacuum swing adsorption).

Oxygen gas can also be produced through electrolysis of water into molecular oxygen and hydrogen. DC electricity must be used: if AC is used, the gases in each limb consist of hydrogen and oxygen in the explosive ratio 2:1. Sony VAIO VPCW11AXJ Battery

Contrary to popular belief, the 2:1 ratio observed in the DC electrolysis of acidified water does not prove that the empirical formula of water is H2O unless certain assumptions are made about the molecular formulae of hydrogen and oxygen themselves. A similar method is the electrocatalytic O2evolution from oxides and oxoacids. Sony VAIO VPCW11S1E/P Battery

Chemical catalysts can be used as well, such as in chemical oxygen generators or oxygen candles that are used as part of the life-support equipment on submarines, and are still part of standard equipment on commercial airliners in case of depressurization emergencies.Sony VAIO VPCW11S1E/T Battery

Another air separation technology involves forcing air to dissolve through ceramicmembranes based on zirconium dioxide by either high pressure or an electric current, to produce nearly pure O2 gas.

In large quantities, the price of liquid oxygen in 2001 was approximately $0.21/kg. Since the primary cost of production is the energy cost of liquefying the air, the production cost will change as energy cost varies.Sony VAIO VPCW11S1E/W Battery

For reasons of economy, oxygen is often transported in bulk as a liquid in specially insulated tankers, since one litre of liquefied oxygen is equivalent to 840 liters of gaseous oxygen at atmospheric pressure and 20 °C.Such tankers are used to refill bulk liquid oxygen storage containers, which stand outside hospitals and other institutions with a need for large volumes of pure oxygen gas.Sony VAIO VPCW121AX Battery

Liquid oxygen is passed through heat exchangers, which convert the cryogenic liquid into gas before it enters the building. Oxygen is also stored and shipped in smaller cylinders containing the compressed gas; a form that is useful in certain portable medical applications and oxy-fuel welding and cutting.Sony VAIO VPCW126AG Battery

Medical

Uptake of O2 from the air is the essential purpose of respiration, so oxygen supplementation is used in medicine. Treatment not only increases oxygen levels in the patient's blood, but has the secondary effect of decreasing resistance to blood flow in many types of diseased lungs, easing work load on the heart.Sony VAIO VPCW127JC/P Battery

Oxygen therapy is used to treat emphysema, pneumonia, some heart disorders (congestive heart failure), some disorders that cause increased pulmonary artery pressure, and any disease that impairs the body's ability to take up and use gaseous oxygen.

Treatments are flexible enough to be used in hospitals, the patient's home, or increasingly by portable devices.Sony VAIO VPCW127JC/T Battery

Oxygen tents were once commonly used in oxygen supplementation, but have since been replaced mostly by the use of oxygen masks or nasal cannulas.

Hyperbaric (high-pressure) medicine uses special oxygen chambers to increase the partial pressure of O2 around the patient and, when needed, the medical staff.Sony VAIO VPCW127JC/W Battery

Carbon monoxide poisoning, gas gangrene, and decompression sickness (the 'bends') are sometimes treated using these devices. Increased O2 concentration in the lungs helps to displace carbon monoxide from the heme group ofhemoglobin. Oxygen gas is poisonous to the anaerobic bacteria that cause gas gangrene, so increasing its partial pressure helps kill them.Sony VAIO VPCW127JC/WZ Battery

Decompression sickness occurs in divers who decompress too quickly after a dive, resulting in bubbles of inert gas, mostly nitrogen and helium, forming in their blood. Increasing the pressure of O2 as soon as possible is part of the treatment.

Oxygen is also used medically for patients who require mechanical ventilation, often at concentrations above the 21% found in ambient air.Sony VAIO VPCW12AAJ Battery

Life support and recreational use

A notable application of O2 as a low-pressure breathing gas is in modern space suits, which surround their occupant's body with pressurized air. These devices use nearly pure oxygen at about one third normal pressure, resulting in a normal blood partial pressure of O2.Sony VAIO VPCW12AKJ Battery

This trade-off of higher oxygen concentration for lower pressure is needed to maintain flexible spacesuits.

Scuba divers and submariners also rely on artificially delivered O2, but most often use normal pressure, and/or mixtures of oxygen and air.Sony VAIO VPCW12AVJ Battery

Pure or nearly pure O2 use in diving at higher-than-sea-level pressures is usually limited to rebreather, decompression, or emergency treatment use at relatively shallow depths (~6 meters depth, or less). Deeper diving requires significant dilution of O2with other gases, such as nitrogen or helium, to help prevent oxygen toxicity.Sony VAIO VPCW12S1E/P Battery

People who climb mountains or fly in non-pressurized fixed-wing aircraft sometimes have supplemental O2 supplies. Passengers traveling in (pressurized) commercial airplanes have an emergency supply of O2 automatically supplied to them in case of cabin depressurization. Sony VAIO VPCW12S1E/T Battery

Sudden cabin pressure loss activates chemical oxygen generators above each seat, causing oxygen masks to drop. Pulling on the masks "to start the flow of oxygen" as cabin safety instructions dictate, forces iron filings into the sodium chlorate inside the canister. A steady stream of oxygen gas is then produced by the exothermic reaction.Sony VAIO VPCW12S1E/W Battery

Oxygen, as a supposed mild euphoric, has a history of recreational use in oxygen bars and in sports. Oxygen bars are establishments, found in Japan, California, and Las Vegas, Nevada since the late 1990s that offer higher than normal O2 exposure for a fee.Sony VAIO VPCW213AG/L Battery

Professional athletes, especially in American football, also sometimes go off field between plays to wear oxygen masks in order to get a "boost" in performance. The pharmacological effect is doubtful; a placebo effect is a more likely explanation.Available studies support a performance boost from enriched O2 mixtures only if they are breathed during aerobic exercise.Sony VAIO VPCW213AG/P Battery

Other recreational uses that do not involve breathing the gas include pyrotechnic applications, such as George Goble's five-second ignition of barbecue grills.

Industrial

Smelting of iron ore into steel consumes 55% of commercially produced oxygen.Sony VAIO VPCW213AG/T Battery

In this process, O2 is injected through a high-pressure lance into molten iron, which removes sulfur impurities and excess carbon as the respective oxides, SO2 and CO2. The reactions are exothermic, so the temperature increases to 1,700 °C.

Another 25% of commercially produced oxygen is used by the chemical industry.Sony VAIO VPCW213AG/W Battery

Ethylene is reacted with O2 to create ethylene oxide, which, in turn, is converted into ethylene glycol; the primary feeder material used to manufacture a host of products, including antifreeze and polyester polymers (the precursors of many plastics and fabrics).Sony VAIO VPCW215AG/L Battery

Most of the remaining 20% of commercially produced oxygen is used in medical applications, metal cutting and welding, as an oxidizer in rocket fuel, and in water treatment. Oxygen is used in oxyacetylene welding burning acetylene with O2 to produce a very hot flame. Sony VAIO VPCW217JC Battery

In this process, metal up to 60 cm thick is first heated with a small oxy-acetylene flame and then quickly cut by a large stream of O2. Larger rockets use liquid oxygen as their oxidizer, which is mixed and ignited with the fuel for propulsion.Sony VAIO VPCW217JC/L Battery

Scientific

Paleoclimatologists measure the ratio of oxygen-18 and oxygen-16 in the shells and skeletons of marine organisms to determine what the climate was like millions of years ago (see oxygen isotope ratio cycle). Seawater molecules that contain the lighter isotope, oxygen-16, evaporate at a slightly faster rate than water molecules containing the 12% heavier oxygen-18;Sony VAIO VPCW217JC/P Battery

this disparity increases at lower temperatures. During periods of lower global temperatures, snow and rain from that evaporated water tends to be higher in oxygen-16, and the seawater left behind tends to be higher in oxygen-18. Marine organisms then incorporate more oxygen-18 into their skeletons and shells than they would in a warmer climate.Sony VAIO VPCW217JC/T Battery

Paleoclimatologists also directly measure this ratio in the water molecules of ice coresamples that are up to several hundreds of thousands of years old.

Planetary geologists have measured different abundances of oxygen isotopes in samples from the Earth, the Moon, Mars, and meteorites, Sony VAIO VPCW217JC/W Battery

but were long unable to obtain reference values for the isotope ratios in the Sun, believed to be the same as those of the primordial solar nebula. However, analysis of a silicon wafer exposed to the solar wind in space and returned by the crashed Genesis spacecraft has shown that the Sun has a higher proportion of oxygen-16 than does the Earth. Sony VAIO VPCW218JC Battery

The measurement implies that an unknown process depleted oxygen-16 from the Sun's disk of protoplanetary material prior to the coalescence of dust grains that formed the Earth.

Oxygen presents two spectrophotometric absorption bands peaking at the wavelengths 687 and 760 nm. Sony VAIO VPCW218JC/L Battery

Some remote sensing scientists have proposed using the measurement of the radiance coming from vegetation canopies in those bands to characterize plant health status from a satellite platform. This approach exploits the fact that in those bands it is possible to discriminate the vegetation's reflectance from its fluorescence, which is much weaker.Sony VAIO VPCW218JC/P Battery

The measurement is technically difficult owing to the low signal-to-noise ratio and the physical structure of vegetation; but it has been proposed as a possible method of monitoring the carbon cycle from satellites on a global scale.

Compounds

The oxidation state of oxygen is ?2 in almost all known compounds of oxygen. Sony VAIO VPCW218JC/T Battery

The oxidation state ?1 is found in a few compounds such asperoxides. Compounds containing oxygen in other oxidation states are very uncommon: ?1/2 (superoxides), ?1/3 (ozonides), 0 (elemental, hypofluorous acid), +1/2 (dioxygenyl), +1 (dioxygen difluoride), and +2 (oxygen difluoride).Sony VAIO VPCW218JC/W Battery

Oxides and other inorganic compounds

Water (H2O) is the oxide of hydrogen and the most familiar oxygen compound. Hydrogen atoms are covalently bonded to oxygen in a water molecule but also have an additional attraction (about 23.3 kJ·mol?1 per hydrogen atom) to an adjacent oxygen atom in a separate molecule.Sony VAIO VPCW219AJ/L Battery

These hydrogen bonds between water molecules hold them approximately 15% closer than what would be expected in a simple liquid with just van der Waals forces.

Due to its electronegativity, oxygen forms chemical bonds with almost all other elements at elevated temperatures to give corresponding oxides. Sony VAIO VPCW219AJ/P Battery

However, some elements readily form oxides at standard conditions for temperature and pressure; the rusting of iron is an example. The surface of metals like aluminium and titanium are oxidized in the presence of air and become coated with a thin film of oxide that passivates the metal and slows further corrosion.Sony VAIO VPCW219AJ/W Battery

Some of the transition metal oxides are found in nature as non-stoichiometric compounds, with a slightly less metal than the chemical formulawould show. For example, the natural occurring FeO (wüstite) is actually written as Fe1 ? xO, where xis usually around 0.05.Sony VAIO VPCW21AAJ Battery

Oxygen as a compound is present in the atmosphere in trace quantities in the form of carbon dioxide (CO2). The earth's crustalrock is composed in large part of oxides of silicon (silica SiO2, found in granite and sand), aluminium (aluminium oxide Al2O3, inbauxite and corundum), iron (iron(III) oxide Fe2O3, in hematite and rust) and other metals.Sony VAIO VPCW21AKJ Battery

The rest of the Earth's crust is also made of oxygen compounds, in particular calcium carbonate (in limestone) and silicates (infeldspars). Water-soluble silicates in the form of Na4SiO4, Na2SiO3, and Na2Si2O5 are used as detergents and adhesives.Sony VAIO VPCW21AVJ Battery

Oxygen also acts as a ligand for transition metals, forming metal–O2 bonds with the iridium atom in Vaska's complex, with the platinum in PtF6, and with the iron center of the heme group of hemoglobin.

Organic compounds and biomolecules

Among the most important classes of organic compounds that contain oxygen are (where "R" is an organic group):Sony VAIO VPCY115FGS Battery

alcohols (R-OH); ethers (R-O-R); ketones (R-CO-R); aldehydes (R-CO-H);carboxylic acids (R-COOH); esters (R-COO-R); acid anhydrides (R-CO-O-CO-R); and amides(R-C(O)-NR2). There are many important organic solvents that contain oxygen, including:Sony VAIO VPCY115FX/BI Battery

acetone, methanol, ethanol, isopropanol, furan, THF, diethyl ether, dioxane, ethyl acetate,DMF, DMSO, acetic acid, and formic acid. Acetone ((CH3)2CO) and phenol (C6H5OH) are used as feeder materials in the synthesis of many different substances. Other important organic compounds that contain oxygen are:Sony VAIO VPCY115FXBI Battery

glycerol, formaldehyde, glutaraldehyde, citric acid, acetic anhydride, and acetamide. Epoxides are ethers in which the oxygen atom is part of a ring of three atoms.

Oxygen reacts spontaneously with many organic compounds at or below room temperature in a process called autoxidation.Sony VAIO VPCY118EC Battery

Most of the organic compounds that contain oxygen are not made by direct action of O2. Organic compounds important in industry and commerce that are made by direct oxidation of a precursor include ethylene oxide and peracetic acid.

The element is found in almost all biomolecules that are important to (or generated by) life. Sony VAIO VPCY118GX/BI Battery

Only a few common complex biomolecules, such as squalene and the carotenes, contain no oxygen. Of the organic compounds with biological relevance,carbohydrates contain the largest proportion by mass of oxygen. All fats, fatty acids, amino acids, and proteins contain oxygen (due to the presence of carbonyl groups in these acids and their ester residues). Sony VAIO VPCY119FJ/S Battery

Oxygen also occurs in phosphate (PO3?4) groups in the biologically important energy-carrying molecules ATP and ADP, in the backbone and the purines (except adenine) and pyrimidines of RNA and DNA, and in bones as calcium phosphate andhydroxylapatite.Sony VAIO VPCY11AFJ Battery

Toxicity

Oxygen gas (O2) can be toxic at elevated partial pressures, leading to convulsionsand other health problems. Oxygen toxicity usually begins to occur at partial pressures more than 50 kilopascals (kPa), or 2.5 times the normal sea-levelO2 partial pressure of about 21 kPa (equal to about 50% oxygen composition at standard pressure). Sony VAIO VPCY11AGJ Battery

This is not a problem except for patients on mechanical ventilators, since gas supplied through oxygen masks in medical applications is typically composed of only 30%–50% O2 by volume (about 30 kPa at standard pressure). (although this figure also is subject to wide variation, depending on type of mask).Sony VAIO VPCY11AHJ Battery

At one time, premature babies were placed in incubators containing O2-rich air, but this practice was discontinued after some babies were blinded by it.

Breathing pure O2 in space applications, such as in some modern space suits, or in early spacecraft such as Apollo, causes no damage due to the low total pressures used.Sony VAIO VPCY11AVJ Battery

In the case of spacesuits, the O2 partial pressure in the breathing gas is, in general, about 30 kPa (1.4 times normal), and the resulting O2 partial pressure in the astronaut's arterial blood is only marginally more than normal sea-level O2 partial pressure (for more information on this, see space suit and arterial blood gas).Sony VAIO VPCY11M1E/S Battery

Oxygen toxicity to the lungs and central nervous system can also occur in deep scuba diving and surface supplied diving. Prolonged breathing of an air mixture with an O2 partial pressure more than 60 kPa can eventually lead to permanent pulmonary fibrosis.Sony VAIO VPCY11S1E Battery

Exposure to a O2 partial pressures greater than 160 kPa (about 1.6 atm) may lead to convulsions (normally fatal for divers). Acute oxygen toxicity (causing seizures, its most feared effect for divers) can occur by breathing an air mixture with 21% O2 at 66 m or more of depth; the same thing can occur by breathing 100% O2 at only 6 m.Sony VAIO VPCY11V9E/S Battery

Combustion and other hazards

Highly concentrated sources of oxygen promote rapid combustion. Fire and explosion hazards exist when concentrated oxidants andfuels are brought into close proximity; however, an ignition event, such as heat or a spark, is needed to trigger combustion.Sony VAIO VPCY218EC/BI Battery

Oxygen itself is not the fuel, but the oxidant. Combustion hazards also apply to compounds of oxygen with a high oxidative potential, such as peroxides, chlorates, nitrates, perchlorates, and dichromates because they can donate oxygen to a fire.

Concentrated O2 will allow combustion to proceed rapidly and energetically.Sony VAIO VPCY218EC/G Battery

Steel pipes and storage vessels used to store and transmit both gaseous and liquid oxygen will act as a fuel; and therefore the design and manufacture of O2 systems requires special training to ensure that ignition sources are minimized. The fire that killed the Apollo 1 crew in a launch pad test spread so rapidly because the capsule was pressurized with pure O2 but at slightly more than atmospheric pressure, instead of the1?3 normal pressure that would be used in a mission.Sony VAIO VPCY218EC/L Battery

Liquid oxygen spills, if allowed to soak into organic matter, such as wood, petrochemicals, and asphalt can cause these materials to detonate unpredictably on subsequent mechanical impact. As with other cryogenic liquids, on contact with the human body it can cause frostbites to the skin and the eyes.Sony VAIO VPCY218EC/P Battery

Ozone (O3, pronounced /?o?zo?n/), or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotropeof oxygen that is much less stable than the diatomic allotrope (O2). Ozone in the lower atmosphere is an air pollutant with harmful effects on the respiratory systems of animals and will burn sensitive plants;Sony VAIO VPCY21S1E/L Battery

however, the ozone layer in the upper atmosphere is beneficial, preventing potentially damaging electromagnetic radiation from reaching the Earth's surface. Ozone is present in low concentrations throughout the Earth's atmosphere. It has many industrial and consumer applications.Sony VAIO VPCY21S1E/P Battery

History

Ozone, the first allotrope of a chemical element to be recognized, was proposed as a distinct chemical substance by Christian Friedrich Schönbein in 1840, who named it after the Greek verb ozein (?????, "to smell"), from the peculiar odor inlightning storms.Sony VAIO VPCY21S1E/SI Battery

The formula for ozone, O3, was not determined until 1865 by Jacques-Louis Soret[5] and confirmed by Schönbein in 1867.

Physical properties

Ozone is a pale blue gas, slightly soluble in water and much more soluble in inert non-polar solvents such as carbon tetrachloride or fluorocarbons, where it forms a blue solution. At 161 K (–112 °C), it condenses to form a dark blue liquid.Sony VAIO VPCZ110 Battery

It is dangerous to allow this liquid to warm to its boiling point, because both concentrated gaseous ozone and liquid ozone can detonate. At temperatures below 80 K (–193 °C), it forms a violet-black solid.

Most people can detect about 0.01 ?mol/mol of ozone in air where it has a very specific sharp odor somewhat resembling chlorine bleach.Sony VAIO VPCZ110GB/BI Battery

Exposure of 0.1 to 1 ?mol/mol produces headaches, burning eyes, and irritation to the respiratory passages. Even low concentrations of ozone in air are very destructive to organic materials such as latex, plastics, and animal lung tissue.

Ozone is diamagnetic, which means that its electrons are all paired. In contrast, O2 is paramagnetic, containing two unpaired electrons.Sony VAIO VPCZ112GD/S Battery

Structure

According to experimental evidence from microwave spectroscopy, ozone is a bent molecule, with C2v symmetry (similar to thewater molecule). The O – O distances are 127.2 pm. The O – O – O angle is 116.78°. The central atom is sp² hybridized with one lone pair. Ozone is a polar molecule with a dipole moment of 0.53 D.Sony VAIO VPCZ112GX/S Battery

The bonding can be expressed as a resonancehybrid with a single bond on one side and double bond on the other producing an overall bond order of 1.5 for each side.

Ozone in Earth's atmosphere

The standard way to express total ozone levels (the amount of ozone in a vertical column) in the atmosphere is by using Dobson units. Point measurements are reported as mole fractions in nmol/mol (parts per billion, ppb) or as concentrations in ?g/m3.Sony VAIO VPCZ114GX/S Battery

Ozone layer

The highest levels of ozone in the atmosphere are in the stratosphere, in a region also known as the ozone layer between about 10 km and 50 km above the surface (or between about 6 and 31 miles). Sony VAIO VPCZ115 Battery

Here it filters out photons with shorter wavelengths (less than 320 nm) of ultraviolet light, also called UV rays, (270 to 400 nm) from the Sun that would be harmful to most forms of lifein large doses. These same wavelengths are also among those responsible for the production of vitamin D in humans. Sony VAIO VPCZ115FC/B Battery

Ozone in the stratosphere is mostly produced from ultraviolet rays reacting with oxygen:

O2 + photon (radiation < 240 nm) ? 2 O

O + O2 + M ? O3 + M

It is destroyed by the reaction with atomic oxygen:

O3 + O ? 2 O2

The latter reaction is catalysed by the presence of certain free radicals, of which the most important are hydroxyl (OH), nitric oxide (NO) and atomic chlorine (Cl) and bromine (Br). Sony VAIO VPCZ115FC/S Battery

In recent decades the amount of ozone in the stratosphere has been declining mostly because of emissions of CFCs and similar chlorinated and brominated organic molecules, which have increased the concentration of ozone-depleting catalysts above the natural background. Ozone only makes up 0.00006% of the atmosphere.Sony VAIO VPCZ116 Battery

Low level ozone

Low level ozone (or tropospheric ozone) is an atmospheric pollutant. It is not emitted directly by car engines or by industrial operations, but formed by the reaction of sunlight on air containing hydrocarbons and nitrogen oxides that react to form ozone directly at the source of the pollution or many kilometers down wind.Sony VAIO VPCZ116GX/S Battery

Ozone reacts directly with some hydrocarbons such as aldehydes and thus begins their removal from the air, but the products are themselves key components of smog. Ozone photolysis by UV light leads to production of the hydroxyl radical OH and this plays a part in the removal of hydrocarbons from the air, Sony VAIO VPCZ117 Battery

but is also the first step in the creation of components of smog such asperoxyacyl nitrates which can be powerful eye irritants. The atmospheric lifetime of tropospheric ozone is about 22 days; its main removal mechanisms are being deposited to the ground, the above mentioned reaction giving OH, and by reactions with OH and the peroxy radical HO2· (Stevenson et al., 2006).Sony VAIO VPCZ117FC/B Battery

There is evidence of significant reduction in agricultural yields because of increased ground-level ozone and pollution which interferes with photosynthesis and stunts overall growth of some plant species. The United States Environmental Protection Agency is proposing a secondary regulation to reduce crop damage, in addition to the primary regulation designed for the protection of human health.Sony VAIO VPCZ118 Battery

Certain examples of cities with elevated ozone readings are Houston, Texas, and Mexico City, Mexico. Houston has a reading of around 41 nmol/mol, while Mexico City is far more hazardous, with a reading of about 125 nmol/mol.Sony VAIO VPCZ118GC/B Battery

Ozone cracking

Ozone gas attacks any polymer possessing olefinic or double bonds within its chain structure, such as natural rubber, nitrile rubber, and styrene-butadiene rubber. Products made using these polymers are especially susceptible to attack, which causes cracks to grow longer and deeper with time,Sony VAIO VPCZ118GX/S Battery

the rate of crack growth depending on the load carried by the product and the concentration of ozone in the atmosphere. Such materials can be protected by adding antiozonants, such as waxes, which bond to the surface to create a protective film or blend with the material and provide long term protection.Sony VAIO VPCZ119 Battery

Ozone cracking used to be a serious problem in car tires for example, but the problem is now seen only in very old tires. On the other hand, many critical products likegaskets and O-rings may be attacked by ozone produced within compressed air systems. Sony VAIO VPCZ119FJ/S Battery

Fuel lines are often made from reinforced rubber tubing and may also be susceptible to attack, especially within engine compartments where low levels of ozone are produced from electrical equipment. Storing rubber products in close proximity to DC electric motors can accelerate the rate at which ozone cracking occurs.Sony VAIO VPCZ119GC/X Battery

The commutator of the motor creates sparks which in turn produce ozone.

Ozone as a greenhouse gas

Although ozone was present at ground level before the Industrial Revolution, peak concentrations are now far higher than the pre-industrial levels, and even background concentrations well away from sources of pollution are substantially higher.Sony VAIO VPCZ119L Battery

This increase in ozone is of further concern because ozone present in the upper troposphere acts as a greenhouse gas, absorbing some of the infrared energy emitted by the earth. Quantifying the greenhouse gas potency of ozone is difficult because it is not present in uniform concentrations across the globe.Sony VAIO VPCZ119R/B Battery

However, the most widely accepted scientific assessments relating to climate change(e.g. the Intergovernmental Panel on Climate Change Third Assessment Report ) suggest that the radiative forcing of tropospheric ozone is about 25% that of carbon dioxide.Sony VAIO VPCZ119R/S Battery

The annual global warming potential of tropospheric ozone is between 918-1022 tons carbon dioxide equivalent/tons tropospheric ozone. This means on a per-molecule basis, ozone in the troposphere has a radiative forcing effect roughly 1,000 times as strong as carbon dioxide.Sony VAIO VPCZ11AFJ Battery

However, tropospheric ozone is a short-livedgreenhouse gas, which decays in the atmosphere much more quickly than carbon dioxide. This means that over a 20 year horizon, the global warming potential of tropospheric ozone is much less, roughly 62 to 69 tons carbon dioxide equivalent / tons tropospheric ozone.Sony VAIO VPCZ11AGJ Battery

Because of its short-lived nature, tropospheric ozone does not have strong global effects, but has very strong radiative forcing effects on regional scales. In fact, there are regions of the world where tropospheric ozone has a radiative forcing up to 150% of carbon dioxide.Sony VAIO VPCZ11AVJ Battery

Air pollution

Ground-level ozone is created near the Earth's surface by the action of daylight UV rays on a group of pollutants called ozone precursors. There is a great deal of evidence to show that ground level ozone can harm lung function and irritate the respiratory system.Sony VAIO VPCZ11CGX/X Battery

Exposure to ozone and the pollutants that produce it is linked to premature death, asthma, bronchitis, heart attack, and other cardiopulmonary problems.

Long-term exposure to ozone has been shown to increase risk of death from respiratory illness. Sony VAIO VPCZ11DGX/SJ Battery

A study of 450,000 people living in United States cities showed a significant correlation between ozone levels and respiratory illness over the 18-year follow-up period. The study revealed that people living in cities with high ozone levels such as Houston or Los Angeles had an over 30% increased risk of dying from lung disease.Sony VAIO VPCZ11FHX/XQ Battery

Air quality guidelines such as those from the World Health Organization, the United States Environmental Protection Agency (EPA) and the European Union are based on detailed studies designed to identify the levels that can cause measurable ill health effects.

According to scientists with the EPA, susceptible people can be adversely affected by ozone levels as low as 40 nmol/mol.Sony VAIO VPCZ11V9R/B Battery

In the EU, the current target value for ozone concentrations is 120 µg/m³ which is about 60 nmol/mol. This target applies to all member states in accordance with Directive 2008/50/EC. Ozone concentration is measured as a maximum daily mean of 8 hour averages and the target should not be exceeded on more than 25 calendar days per year, starting from January 2010. Sony VAIO VPCZ11X9E/B Battery

Whilst the directive requires in the future a strict compliance with 120 µg/m³ limit (i.e. mean ozone concentration not to be exceeded on any day of the year), there is no date set for this requirement and this is treated as a long-term objective. Sony VAIO VPCZ11Z9E/B Battery

The Clean Air Act directs the EPA to set National Ambient Air Quality Standards for several pollutants, including ground-level ozone, and counties out of compliance with these standards are required to take steps to reduce their levels. In May 2008, the EPA lowered its ozone standard from 80 nmol/mol to 75 nmol/mol. Sony VAIO VPCZ125GX/S Battery

This proved controversial, since the Agency's own scientists and advisory board had recommended lowering the standard to 60 nmol/mol, and the World Health Organization recommends 51 nmol/mol. Many public health and environmental groups also supported the 60 nmol/mol standard.Sony VAIO VPCZ127FC Battery

On January 7, 2010, the U.S. Environmental Protection Agency (EPA) announced proposed revisions to the National Ambient Air Quality Standard (NAAQS) for the pollutant ozone, the principal component of smog:

... EPA proposes that the level of the 8-hour primary standard, which was set at 0.075 ?mol/mol in the 2008 final rule, should instead be set at a lower level within the range of 0.060 to 0.070 ?mol/mol,Sony VAIO VPCZ128GC Battery

to provide increased protection for children and other ‘‘at risk’’ populations against an array of O3- related adverse health effects that range from decreased lung function and increased respiratory symptoms to serious indicators of respiratory morbidity including emergency department visits and hospital admissions for respiratory causes,Sony VAIO VPCZ12M9E/B Battery

and possibly cardiovascular-related morbidity as well as total non- accidental and cardiopulmonary mortality...

The EPA has developed an Air Quality Index (AQI) to help explain air pollution levels to the general public. Under the current standards, eight-hour average ozone mole fractions of 85 to 104 nmol/mol are described as "unhealthy for sensitive groups," 105 nmol/mol to 124 nmol/mol as "unhealthy," and 125 nmol/mol to 404 nmol/mol as "very unhealthy."Sony VAIO VPCZ13M9E/B Battery

Ozone can also be present in indoor air pollution, partly as a result of electronic equipment such as photocopiers. A connection has also been known to exist between the increased pollen, fungal spores, and ozone caused by thunderstorms and hospital admissions of asthma sufferers.Sony VAIO VPCZ13V9E/X Battery

In the Victorian era, one British folk myth held that the smell of the sea was caused by ozone. In fact, the characteristic "smell of the sea" is caused by dimethyl sulfide a chemical generated by phytoplankton. Victorian British folk considered the resulting smell "bracing," but in high concentrations, dimethyl sulfide is actually toxic.Sony VAIO VPCZ13Z9E/X Battery

Physiology

Ozone, along with reactive forms of oxygen such as superoxide, singlet oxygen, hydrogen peroxide, and hypochlorite ions, is naturally produced by white blood cellsand other biological systems (such as the roots of marigolds) as a means of destroying foreign bodies. Ozone reacts directly with organic double bonds. Sony VAIO VPCZZZHJ Battery

Also, when ozone breaks down to dioxygen it gives rise to oxygen free radicals, which are highly reactive and capable of damaging many organic molecules. Moreover, it is believed that the powerful oxidizing properties of ozone may be a contributing factor of inflammation. Sony VAIO VPZ117 Battery

The cause-and-effect relationship of how the ozone is created in the body and what it does is still under consideration and still subject to various interpretations, since other body chemical processes can trigger some of the same reactions. A team headed by Dr. Paul Wentworth Jr. of the Department of Chemistry at the Scripps Research Institute has shown evidence linking the antibody-catalyzed water-oxidation pathway of the human immune response to the production of ozone. Sony VAIO VPZ118 Battery

In this system, ozone is produced by antibody-catalyzed production oftrioxidane from water and neutrophil-produced singlet oxygen.

When inhaled, ozone reacts with compounds lining the lungs to form specific, cholesterol-derived metabolites that are thought to facilitate the build-up and pathogenesis of atherosclerotic plaques (a form of heart disease).Sony VAIO VPZ119 Battery

These metabolites have been confirmed as naturally occurring in human atherosclerotic arteries and are categorized into a class of secosterols termed atheronals, generated by ozonolysis of cholesterol's double bond to form a 5,6 secosterol as well as a secondary condensation product via aldolization.Sony VPCM11M1E/B Battery

Ozone has been implicated to have an adverse effect on plant growth: "... ozone reduced total chlorophylls, carotenoid and carbohydrate concentration, and increased 1-aminocyclopropane-1-carboxylic acid (ACC) content and ethylene production.Sony VPCM11M1E/W Battery

In treated plants, the ascorbate leaf pool was decreased, while lipid peroxidation and solute leakage were significantly higher than in ozone-free controls. The data indicated that ozone triggered protective mechanisms against oxidative stress in citrus."

Safety regulations

Due to the strongly oxidizing properties of ozone, ozone is a primary irritant, affecting especially the eyes and respiratory systems and can be hazardous at even low concentrations. Sony VPCM12M1E/L Battery

The Canadian Center for Occupation Safety and Health reports that:

"Even very low concentrations of ozone can be harmful to the upper respiratory tract and the lungs. The severity of injury depends on both by the concentration of ozone and the duration of exposure. Severe and permanent lung injury or death could result from even a very short-term exposure to relatively low concentrations." Sony VPCM12M1E/P Battery

To protect workers potentially exposed to ozone, U.S. Occupational Safety and Health Administration has established a permissible exposure limit (PEL) of 0.1 ?mol/mol (29 CFR 1910.1000 table Z-1), calculated as an 8 hour time weighted average. Sony VPCM12M1E/W Battery

Higher concentrations are especially hazardous and NIOSH has established an Immediately Dangerous to Life and Health Limit (IDLH) of 5 ?mol/mol. Work environments where ozone is used or where it is likely to be produced should have adequate ventilation and it is prudent to have a monitor for ozone that will alarm if the concentration exceeds the OSHA PEL. Sony VPCM13M1E/L Battery

Continuous monitors for ozone are available from several suppliers.

Elevated ozone exposure can occur on passenger aircraft, with levels depending on altitude and atmospheric turbulence. United States Federal Aviation Authorityregulations set a limit of 250 nmol/mol with a maximum four-hour average of 100 nmol/mol.Sony VPCM13M1E/P Battery

Some planes are equipped with ozone converters in the ventilation system to reduce passenger exposure.

Production

Ozone often forms in nature under conditions where O2 will not react. Ozone used in industry is measured in ?mol/mol (ppm, parts per million), nmol/mol (ppb, parts per billion), ?g/m3, mg/hr (milligrams per hour) or weight percent. Sony VPCM13M1E/W Battery

The regime of applied concentrations ranges from 1 to 5% in air and from 6 to 14% in oxygen for older generation methods. New electrolytic methods can achieve up 20 to 30% dissolved ozone concentrations in output water.

Temperature and humidity plays a large role in how much ozone is being produced using traditional generation methods such as corona discharge and ultraviolet light. Sony VAIO VGN-Z11MN/B Battery

Old generation methods will produce less than 50% its nominal capacity if operated with humid ambient air than when it operates in very dry air. New generators using electrolytic methods can achieve higher purity and dissolution through using water molecules as the source of ozone production.Sony VAIO VGN-Z11VN/X Battery

Corona discharge method

This is the most common type of ozone generator for most industrial and personal uses. While variations of the "hot spark" coronal discharge method of ozone production exist, including medical grade and industrial grade ozone generators, these units usually work by means of a corona discharge tube.Sony VAIO VGN-Z11WN/B Battery

They are typically cost-effective and do not require an oxygen source other than the ambient air to produce ozone concentrations of 3-6%. Fluctuations in ambient air, due to weather or other environmental conditions, cause variability in ozone production. However, they also produce nitrogen oxides as a by-product. Sony VAIO VGN-Z11XN/B Battery

Use of an air dryer can reduce or eliminate nitric acid formation by removing water vapor and increase ozone production. Use of an oxygen concentrator can further increase the ozone production and further reduce the risk of nitric acid formation by removing not only the water vapor, but also the bulk of the nitrogen.Sony VAIO VGN-Z15 Battery

Ultraviolet light

UV ozone generators, or vacuum-ultraviolet (VUV) ozone generators, employ a light source that generates a narrow-band ultraviolet light, a subset of that produced by the Sun. The Sun's UV sustains the ozone layer in the stratosphere of Earth.Sony VAIO VGN-Z15N Battery

While standard UV ozone generators tend to be less expensive, they usually produce ozone with a concentration of about 0.5% or lower. Another disadvantage of this method is that it requires the air (oxygen) to be exposed to the UV source for a longer amount of time, and any gas that is not exposed to the UV source will not be treated.Sony VAIO VGN-Z17 Battery

This makes UV generators impractical for use in situations that deal with rapidly moving air or water streams (in-duct airsterilization, for example). Production of ozone is one of the potential dangers of ultraviolet germicidal irradiation. VUV ozone generators are used in swimming pool and spa applications ranging to millions of gallons of water.Sony VAIO VGN-Z17N Battery

VUV ozone generators, unlike corona discharge generators, do not produce harmful nitrogen by-products and also unlike corona discharge systems, VUV ozone generators work extremely well in humid air environments. There is also not normally a need for expensive off-gas mechanisms, and no need for air driers or oxygen concentrators which require extra costs and maintenance.Sony VAIO VGN-Z19 Battery

Cold plasma

In the cold plasma method, pure oxygen gas is exposed to a plasma created by dielectric barrier discharge. The diatomic oxygen is split into single atoms, which then recombine in triplets to form ozone.

Cold plasma machines utilize pure oxygen as the input source and produce a maximum concentration of about 5% ozone. Sony VAIO VGN-Z19N Battery

They produce far greater quantities of ozone in a given space of time compared to ultraviolet production. However, because cold plasma ozone generators are very expensive, they are found less frequently than the previous two types.

The discharges manifest as filamentary transfer of electrons (micro discharges) in a gap between two electrodes. Sony VAIO VGN-Z21MN/B Battery

In order to evenly distribute the micro discharges, a dielectric insulator must be used to separate the metallic electrodes and to prevent arcing.

Some cold plasma units also have the capability of producing short-lived allotropes of oxygen which include O4, O5, O6, O7, etc. These species are even more reactive than ordinary O3. Sony VAIO VGN-Z21VN/X Battery

Electrolytic

Electrolytic ozone generation (EOG) splits water molecules into H2, O2, and O3. In most EOG methods, the hydrogen gas will be removed to leave oxygen and ozone as the only reaction products. Therefore, EOG can achieve higher dissolution in water without other competing gases found in corona discharge method, such as nitrogen gases present in ambient air.Sony VAIO VGN-Z21WN/B Battery

This method of generation can achieve concentrations of 20-30% and is independent of air quality because water is used as the starting substrate.

Special considerations

Ozone cannot be stored and transported like other industrial gases (because it quickly decays into diatomic oxygen) and must therefore be produced on site. Sony VAIO VGN-Z21XN Battery

Available ozone generators vary in the arrangement and design of the high-voltage electrodes. At production capacities higher than 20 kg per hour, a gas/water tube heat-exchanger may be utilized as ground electrode and assembled with tubular high-voltage electrodes on the gas-side. Sony VAIO VGN-Z21ZN/X Battery

The regime of typical gas pressures is around 2 barabsolute in oxygen and 3 bar absolute in air. Several megawatts of electrical power may be installed in large facilities, applied as one phase AC current at 50 to 8000 Hz and peak voltages between 3,000 and 20,000 volts. Applied voltage is usually inversely related to the applied frequency.Sony VAIO VGN-Z25 Battery

The dominating parameter influencing ozone generation efficiency is the gas temperature, which is controlled by cooling water temperature and/or gas velocity. The cooler the water, the better the ozone synthesis. The lower the gas velocity, the higher the concentration (but the lower the net ozone produced). Sony VAIO VGN-Z25/B Battery

At typical industrial conditions, almost 90% of the effective power is dissipated as heat and needs to be removed by a sufficient cooling water flow.

Because of the high reactivity of ozone, only few materials may be used like stainless steel (quality 316L), titanium, aluminium (as long as no moisture is present),glass, polytetrafluorethylene, or polyvinylidene fluoride. Sony VAIO VGN-Z25TN/B Battery

Viton may be used with the restriction of constant mechanical forces and absence of humidity (humidity limitations apply depending on the formulation). Hypalon may be used with the restriction that no water come in contact with it, except for normal atmospheric levels.Sony VAIO VGN-Z26TN/B Battery

Embrittlement or shrinkage is the common mode of failure of elastomers with exposure to ozone. Ozone cracking is the common mode of failure of elastomer seals like O-rings.

Silicone rubbers are usually adequate for use as gaskets in ozone concentrations below 1 wt%, such as in equipment for accelerated aging of rubber samples.Sony VAIO VGN-Z27 Battery

Incidental production

Ozone may be formed from O2 by electrical discharges and by action of high energy electromagnetic radiation. Unsuppressed arcing breaks down the chemical bonds of the atmospheric oxygen surrounding the contacts [O2 ? 2O]. Free ions of oxygen in and around the arc recombine to create ozone [O3].Sony VAIO VGN-Z27/B Battery

Certain electrical equipmentgenerate significant levels of ozone. This is especially true of devices using high voltages, such as ionic air purifiers, laser printers, photocopiers, tasers andarc welders. Electric motors using brushes can generate ozone from repeated sparking inside the unit. Sony VAIO VGN-Z27TN/X Battery

Large motors that use brushes, such as those used by elevators or hydraulic pumps, will generate more ozone than smaller motors. Ozone is similarly formed in the Catatumbo lightning storms phenomenon on the Catatumbo River inVenezuela, which helps to replenish ozone in the upper troposphere. Sony VAIO VGN-Z29N Battery

It is the world's largest single natural generator of ozone, lending calls for it to be designated a UNESCO World Heritage Site.

Laboratory production

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 3 molar sulfuric acidelectrolyte. The half cell reactions taking place are:Sony VAIO VGN-Z29N/X Battery

3 H2O ? O3 + 6 H+ + 6 e? (?Eo = ?1.53 V)

6 H+ + 6 e? ? 3 H2 (?Eo = 0 V)

2 H2O ? O2 + 4 H+ + 4 e? (?Eo = ?1.23 V)

In the net reaction, three equivalents of water are converted into one equivalent of ozone and three equivalents of hydrogen. Oxygen formation is a competing reaction.Sony VAIO VGN-Z31MN/B Battery

It can also be "prepared" by high voltage arc. This can be done with an apparatus consisting of two concentric glass tubes sealed together at the top, with in and out spigots at the top and bottom of the outer tube. The inner core should have a length of metal foil inserted into it connected to one side of the power source. Sony VAIO VGN-Z31VN/X Battery

The other side of the power source should be connected to another piece of foil wrapped around the outer tube. Dry O2 should be run through the tube in one spigot. As the O2 is run through one spigot into the apparatus and high voltage is applied to the foil leads, electricity will discharge between the dry dioxygen in the middle and form O3 and O2 out the other spigot. Sony VAIO VGN-Z31WN/B Battery

The reaction can be summarized as follows:

Industry

The largest use of ozone is in the preparation of pharmaceuticals, synthetic lubricants, and many other commercially useful organic compounds, where it is used to sever carbon-carbon bonds. It can also be used for bleaching substances and for killing microorganisms in air and water sources.Sony VAIO VGN-Z31ZN/X Battery

Many municipal drinking water systems kill bacteria with ozone instead of the more common chlorine. Ozone has a very high oxidation potential. Ozone does not form organochlorine compounds, nor does it remain in the water after treatment. Ozone can form the suspected carcinogen [bromate] in source water with high bromide concentrations.Sony VAIO VGN-Z35 Battery

The Safe Drinking Water Act mandates that these systems introduce an amount of chlorine to maintain a minimum of 0.2 ?mol/mol residual free chlorine in the pipes, based on results of regular testing. Where electrical power is abundant, ozone is a cost-effective method of treating water, since it is produced on demand and does not require transportation and storage of hazardous chemicals.Sony VAIO VGN-Z35/B Battery

Once it has decayed, it leaves no taste or odor in drinking water.

Although low levels of ozone have been advertised to be of some disinfectant use in residential homes, the concentration of ozone in dry air required to have a rapid, substantial effect on airborne pathogens exceeds safe levels recommended by the U.S. Sony VAIO VGN-Z35TN/B Battery

Occupational Safety and Health Administration and Environmental Protection Agency. Humidity control can vastly improve both the killing power of the ozone and the rate at which it decays back to oxygen (more humidity allows more effectiveness). Spore forms of most pathogens are very tolerant of atmospheric ozone in concentrations where asthma patients start to have issues.Sony VAIO VGN-Z36GD Battery

Industrially, ozone is used to:

• Disinfect laundry in hospitals, food factories, care homes etc.;
• Disinfect water in place of chlorine
• Deodorize air and objects, such as after a fire. This process is extensively used in fabric restoration
• Kill bacteria on food or on contact surfaces;Sony VAIO VGN-Z36GD/B Battery
• Sanitize swimming pools and spas
• Kill insects in stored grain
• 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 "colour");Sony VAIO VGN-Z36GD/J Battery
• Provide an aid to flocculation (agglomeration of molecules, which aids in filtration, where the iron and arsenic are removed);
• Manufacture chemical compounds via chemical synthesis
• Clean and bleach fabrics (the former use is utilized in fabric restoration; the latter use is patented);
• Assist in processing plastics to allow adhesion of inks;Sony VAIO VGN-Z36TD/B Battery
• Age rubber samples to determine the useful life of a batch of rubber;
• Eradicate water borne parasites such as Giardia lamblia and Cryptosporidium in surface water treatment plants.

Ozone is a reagent in many organic reactions in the laboratory and in industry. Ozonolysis is the cleavage of an alkene to carbonyl compounds.Sony VAIO VGN-Z36TD/J Battery

Many hospitals in the U.S. and around the world use large ozone generators to decontaminate operating rooms between surgeries. The rooms are cleaned and then sealed airtight before being filled with ozone which effectively kills or neutralizes all remaining bacteria.Sony VAIO VGN-Z37D Battery

Ozone is used as an alternative to chlorine or chlorine dioxide in the bleaching of wood pulp. It is often used in conjunction with oxygen and hydrogen peroxide to eliminate the need for chlorine-containing compounds in the manufacture of high-quality, white paper.Sony VAIO VGN-Z37D/B Battery

Ozone can be used to detoxify cyanide wastes (for example from gold and silver mining) by oxidizing cyanide to cyanate and eventually to carbon dioxide.

Consumers

Devices generating high levels of ozone, some of which use ionization, are used to sanitize and deodorize uninhabited buildings, rooms, ductwork, woodsheds, and boats and other vehicles.Sony VAIO VGN-Z37GD Battery

In the U.S., air purifiers emitting low levels of ozone have been sold. This kind of air purifier is sometimes claimed to imitate nature's way of purifying the air without filters and to sanitize both it and household surfaces. The United States Environmental Protection Agency (EPA) has declared that there is "evidence to show that at concentrations that do not exceed public health standards,Sony VAIO VGN-Z37GD/X Battery

ozone is not effective at removing many odor-causing chemicals" or "viruses, bacteria, mold, or other biological pollutants." Furthermore, its report states that "results of some controlled studies show that concentrations of ozone considerably higher than these [human safety] standards are possible even when a user follows the manufacturer’s operating instructions."Sony VAIO VGN-Z39D Battery

The government successfully sued one company in 1995, ordering it to stop repeating health claims without supporting scientific studies.

Ozonated water is used to launder clothes and to sanitize food, drinking water, and surfaces in the home. According to the U.S. Sony VAIO VGN-Z39D/X Battery

Food and Drug Administration (FDA), it is "amending the food additive regulations to provide for the safe use of ozone in gaseous and aqueous phases as an antimicrobial agent on food, including meat and poultry." Studies at California Polytechnic University demonstrated that 0.3 ?mol/mol levels of ozone dissolved in filtered tapwater can produce a reduction of more than 99.99% in such food-borne microorganisms as salmonella, E. coli 0157:H7, and Campylobacter.Sony VAIO VGN-Z41MD/B Battery

This quantity is 20,000 times the WHO recommended limits stated above.Ozone can be used to remove pesticide residues from fruits and vegetables.

Ozone is used in homes and hot tubs to kill bacteria in the water and to reduce the amount of chlorine or bromine required by reactivating them to their free state. Sony VAIO VGN-Z41WD/B Battery

Since ozone does not remain in the water long enough, ozone by itself is ineffective at preventing cross-contamination among bathers and must be used in conjunction with halogens. Gaseous ozone created by ultraviolet light or by corona discharge is injected into the water.Sony VAIO VGN-Z45GD/B Battery

Ozone is also widely used in treatment of water in aquariums and fish ponds. Its use can minimize bacterial growth, control parasites, eliminate transmission of some diseases, and reduce or eliminate "yellowing" of the water. Ozone must not come in contact with fish's gill structures. Sony VAIO VGN-Z45TD/B Battery

Natural salt water (with life forms) provides enough "instantaneous demand" that controlled amounts of ozone activate bromide ion to hypobromous acid, and the ozone entirely decays in a few seconds to minutes. If oxygen fed ozone is used, the water will be higher in dissolved oxygen, fish's gill structures will atrophy and they will become dependent on higher dissolved oxygen levels.Sony VAIO VGN-Z46GD/B Battery

Aquaculture

Ozone can be used in aquaculture to facilitate organic breakdown. It is added to recirculating systems to reduce nitrite levels through conversion into nitrate. If nitrite levels in the water are high, nitrites will also accumulate in the blood and tissues of fish, where it interferes with oxygen transport (it causes oxidation of the heme-group of haemoglobin from ferrous(Fe2+) to ferric (Fe3+), making haemoglobin unable to bind O2 ).Sony VAIO VGN-Z46GD/U Battery

Despite these apparent positive effects, ozone use in recirculation systems has been linked to reducing the level of bioavailable iodine in salt water systems, resulting in iodine deficiency symptoms such as goitre and decreased growth in Senegalese sole (Solea senegalensis) larvae.Sony VAIO VGN-Z46MD/B Battery

Ozonate seawater is used for surface disinfection of haddock and Atlantic halibut eggs against nodavirus. Nodavirus is a lethal and vertically transmitted virus which causes severe mortality in fish. Haddock eggs should not be treated with high ozone level as eggs so treated did not hatch and died after 3–4 days.Sony VAIO VGN-Z46SD/B Battery

Agriculture

Ozone application on freshly cut pineapple and banana shows increase in flavonoids and total phenol contents when exposure is up to 20 minutes. Decrease in ascorbic acid content is observed but the positive effect on total phenol content and flavonoids can overcome the negative effect.Sony VAIO VGN-Z46TD/B Battery

Tomatoes upon treatment with ozone shows an increase in ?-carotene, lutein and lycopene.However, ozone application on strawberries in pre-harvest period shows decrease in ascorbic acid content.

Ozone facilitates the extraction of some heavy metals from soil using EDTA. EDTA forms strong, water-soluble coordination compounds with some heavy metals (Pb, Zn) thereby making it possible to dissolve them out from contaminated soil. Sony VAIO VGN-Z46TD/R Battery

If contaminated soil is pre-treated with ozone, the extraction efficacy of Pb, Am and Puincreases by 11-28.9%, 43.5% and 50.7% respectively.Sony VAIO VGN-Z47GD/X Battery,Sony VAIO VGN-Z48GD/X Battery,Sony VAIO VGN-Z48TD/X Battery,Sony VAIO VGN-Z51WG/B Battery,Sony VAIO VGN-Z51XG/B Battery