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oxidation and reduction, complementary chemical reactions characterized by the loss or gain, respectively, of one or more electrons by an atom or molecule. Originally the term oxidation was used to refer to a reaction in which oxygen combined with an element or compound, e.g., the reaction of magnesium with oxygen to form magnesium oxide or the combination of carbon monoxide with oxygen to form carbon dioxide. Similarly, reduction referred to a decrease in the amount of oxygen in a substance or its complete removal, e.g., the reaction of cupric oxide and hydrogen to form copper and water. When an atom or molecule combines with oxygen, it tends to give up electrons to the oxygen in forming a chemical bond. Similarly, when it loses oxygen, it tends to gain electrons. Such changes are now described in terms of changes in the oxidation number, or oxidation state, of the atom or molecule (see valence). Thus oxidation has come to be defined as a loss of electrons or an increase in oxidation number, while reduction is defined as a gain of electrons or a decrease in oxidation number, whether or not oxygen itself is actually involved in the reaction. In the formation of magnesium oxide from magnesium and oxygen, the magnesium atoms have lost two electrons, or the oxidation number has increased from zero to +2. This is also true when magnesium reacts with chlorine to form magnesium chloride. In solution, ferrous iron (oxidation number +2) may be oxidized to ferric iron (oxidation number +3) by the loss of an electron. In the reduction of cupric oxide the oxidation number of copper has changed from +2 to zero by the gain of two electrons. The two processes, oxidation and reduction, occur simultaneously and in chemically equivalent quantities. In the formation of magnesium chloride, for every magnesium atom oxidized by a loss of two electrons, two chlorine atoms are reduced by a gain of one electron each. Oxidation-reduction reactions, called also redox reactions, are most simply balanced in the form of chemical equations by arranging the quantities of the substances involved so that the number of electrons lost by one substance is equaled by the number gained by another substance. In such reactions, the substance losing electrons (undergoing oxidation) is said to be an electron donor, or reductant, since its lost electrons are given to and reduce the other substance. Conversely, the substance that is gaining electrons (undergoing reduction) is said to be an electron acceptor, or oxidant. Common reductants (substances readily oxidized) are the active metals, hydrogen, hydrogen sulfide, carbon, carbon monoxide, and sulfurous acid. Common oxidants (substances readily reduced) include the halogens (especially fluorine and chlorine), oxygen, ozone, potassium permanganate, potassium dichromate, nitric acid, and concentrated sulfuric acid. Some substances are capable of acting either as reductants or as oxidants, e.g., hydrogen peroxide and nitrous acid. The corrosion of metals is a naturally occurring redox reaction. Industrially, many redox reactions are of great importance: combustion of fuels; electrolysis (oxidation occurs at the anode and reduction at the cathode); and metallurgical processes in which free metals are obtained from their ores.

WordNet: redox Top Home > Library > Literature & Language > WordNet Note: click on a word meaning below to see its connections and related words.

The noun has one meaning: Meaning #1: a reversible chemical reaction in which one reaction is an oxidation and the reverse is a reduction Synonyms: oxidation-reduction, oxidoreduction Wikipedia: Redox Top Home > Library > Miscellaneous > Wikipedia

Illustration of a redox reaction Redox (shorthand for reduction-oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane (CH4), or it can be a complex process such as the oxidation of sugar in the human body through a series of very complex electron transfer processes. The term redox comes from the two concepts of reduction and oxidation. It can be explained in simple terms: • •

Oxidation describes the loss of electrons or an increase in oxidation state by a molecule, atom or ion. Reduction describes the gain of electrons or a decrease in oxidation state by a molecule, atom or ion.

Though sufficient for many purposes, these descriptions are not precisely correct. Oxidation and reduction properly refer to a change in oxidation number — the actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. In practice, the transfer of electrons will always cause a change in oxidation number, but there are many reactions that are classed as "redox" even though no electron transfer occurs (such as those involving covalent bonds).

Non-redox reactions, which do not involve changes in formal charge, are known as metathesis reactions.

The two parts of a redox reaction

Rusting iron

A bonfire. Combustion consists of redox reactions involving free radicals.

Contents [hide] •

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1 Oxidizing and reducing agents o 1.1 Oxidizers o 1.2 Reducers 2 Examples of redox reactions o 2.1 Displacement reactions o 2.2 Other examples 3 Redox reactions in industry 4 Redox reactions in biology o 4.1 Redox cycling

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5 Balancing redox reactions o 5.1 Acidic media o 5.2 Basic media 6 See also 7 References

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8 External links

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Oxidizing and reducing agents The chemical way to look at redox processes is that the reductant transfers electrons to the oxidant. Thus, in the reaction, the reductant or reducing agent loses electrons and is oxidized, and the oxidant or oxidizing agent gains electrons and is reduced. The pair of an oxidizing and reducing agent that are involved in a particular reaction is called a redox pair.

Oxidizers Substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants, or oxidizers. Put another way, the oxidant removes electrons from another substance, and is thus itself reduced. And, because it "accepts" electrons, it is also called an electron acceptor. Oxidants are usually chemical substances with elements in high oxidation numbers (e.g., H2O2, MnO4−, CrO3, Cr2O72−, OsO4) or highly electronegative substances that can gain one or two extra electrons by oxidizing a substance (O, F, Cl, Br).

Reducers Substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. Put in another way, the reductant transfers electrons to another substance, and is, thus, oxidized itself. And, because it "donates" electrons it is also called an electron donor. Reductants in chemistry are very diverse. Metal reduction— electropositive elemental metals can be used (Li, Na, Mg, Fe, Zn, Al). These metals donate or give away electrons readily. Reactions-Reducing Agents Other kinds of reductants are hydride transfer reagents (NaBH4, LiAlH4), these reagents are widely used in organic chemistry[1][2], primarily in the reduction of carbonyl compounds to alcohols. Another useful method is reductions involving hydrogen gas (H2) with a palladium, platinum, or nickel catalyst. These catalytic reductions are primarily used in the reduction of carbon-carbon double or triple bonds.

Examples of redox reactions A good example is the reaction between hydrogen and fluorine: H2 + F2 → 2 HF

We can write this overall reaction as two half-reactions: the oxidation reaction: H2 → 2 H+ + 2 e− and the reduction reaction: F2 + 2 e− → 2 F− Analyzing each half-reaction in isolation can often make the overall chemical process clearer. Because there is no net change in charge during a redox reaction, the number of electrons in excess in the oxidation reaction must equal the number consumed by the reduction reaction (as shown above). Elements, even in molecular form, always have an oxidation number of zero. In the first halfreaction, hydrogen is oxidized from an oxidation number of zero to an oxidation number of +1. In the second half-reaction, fluorine is reduced from an oxidation number of zero to an oxidation number of −1. When adding the reactions together the electrons cancel: H2 → 2 H+ + 2 e− F2 + 2 e− → 2 F− H2 + F2 → 2 H+ + 2 F− And the ions combine to form hydrogen fluoride: H2 + F2 → 2 H+ + 2 F− → 2 HF

Displacement reactions Redox occurs in single displacement reactions or substitution reactions. The redox component of these types of reactions is the change of oxidation state (charge) on certain atoms, not the actual exchange of atoms in the compounds. For example, in the reaction between iron and copper(II) sulfate solution: Fe + CuSO4 → FeSO4 + Cu The ionic equation for this reaction is: Fe + Cu2+ → Fe2+ + Cu As two half-equations, it is seen that the iron is oxidized: Fe → Fe2+ + 2 e−

And the copper is reduced: Cu2+ + 2 e− → Cu

Other examples •

The oxidation of iron(II) to iron(III) by hydrogen peroxide in the presence of an acid: Fe2+ → Fe3+ + e− H2O2 + 2 e− → 2 OH− Overall equation: 2 Fe2+ + H2O2 + 2 H+ → 2 Fe3+ + 2 H2O

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The reduction of nitrate to nitrogen in the presence of an acid (denitrification): 2 NO3− + 10 e− + 12 H+ → N2 + 6 H2O

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Oxidation of elemental iron to iron(III) oxide by oxygen (commonly known as rusting, which is similar to tarnishing): 4 Fe + 3 O2 → 2 Fe2O3

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The combustion of hydrocarbons, such as in an internal combustion engine, which produces water, carbon dioxide, some partially oxidized forms such as carbon monoxide and heat energy. Complete oxidation of materials containing carbon produces carbon dioxide.

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In organic chemistry, the stepwise oxidation of a hydrocarbon by oxygen produces water and, successively, an alcohol, an aldehyde or a ketone, a carboxylic acid, and then a peroxide.

Redox reactions in industry The primary process of reducing ore to produce metals is discussed in the article on Smelting. Oxidation is used in a wide variety of industries such as in the production of cleaning products and oxidising ammonia to produce nitric acid, which is used in most fertilizers. Redox reactions are the foundation of electrochemical cells. The production of compact discs depends on a redox reaction, which coats the disc with a thin layer of metal film.

Redox reactions in biology

Top: ascorbic acid (reduced form of Vitamin C) Bottom: dehydroascorbic acid (oxidized form of Vitamin C)

Many important biological processes involve redox reactions. Cellular respiration, for instance, is the oxidation of glucose (C6H12O6) to CO2 and the reduction of oxygen to water. The summary equation for cell respiration is: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O The process of cell respiration also depends heavily on the reduction of NAD+ to NADH and the reverse reaction (the oxidation of NADH to NAD+). Photosynthesis is essentially the reverse of the redox reaction in cell respiration: 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 Biological energy is frequently stored and released by means of redox reactions. Photosynthesis involves the reduction of carbon dioxide into sugars and the oxidation of water into molecular oxygen. The reverse reaction, respiration, oxidizes sugars to produce carbon dioxide and water. As intermediate steps, the reduced carbon compounds are used to reduce nicotinamide adenine dinucleotide (NAD+), which then contributes to the creation of a proton gradient, which drives the synthesis of adenosine triphosphate (ATP) and is maintained by the reduction of oxygen. In animal cells, mitochondria perform similar functions. See Membrane potential article. The term redox state is often used to describe the balance of NAD+/NADH and NADP+/NADPH in a biological system such as a cell or organ. The redox state is reflected in the balance of several sets of metabolites (e.g., lactate and pyruvate, beta-hydroxybutyrate and acetoacetate), whose interconversion is dependent on these ratios. An abnormal redox state can develop in a

variety of deleterious situations, such as hypoxia, shock, and sepsis. Redox signaling involves the control of cellular processes by redox processes. Redox proteins and their genes must be Co-located for Redox Regulation according to the CoRR Hypothesis for the function of DNA in mitochondria and chloroplasts.

Redox cycling A wide variety of aromatic compounds are enzymatically reduced to form free radicals that contain one more electron than their parent compounds. In general, the electron donor is any of a wide variety of flavoenzymes and their coenzymes. Once formed, these anion free radicals reduce molecular oxygen to superoxide, and regenerate the unchanged parent compound. The net reaction is the oxidation of the flavoenzyme's coenzymes and the reduction of molecular oxygen to form superoxide. This catalytic behavior has been described as futile cycle or redox cycling. Examples of redox cycling-inducing molecules are the herbicide paraquat and other viologens and quinones such as menadione. [3]

Balancing redox reactions Describing the overall electrochemical reaction for a redox process requires a balancing of the component half-reactions for oxidation and reduction. For reactions in aqueous solution, this generally involves adding H+, OH−, H2O, and electrons to compensate for the oxidation changes.

Acidic media In acidic media, H+ ions and water are added to half reactions to balance the overall reaction. For example, when manganese(II) reacts with sodium bismuthate: Unbalanced reaction: Mn2+ (aq) + NaBiO3 (s) → Bi3+ (aq) + MnO4− (aq) Oxidation: 4 H2O (l) + Mn2+ (aq) → MnO4− (aq) + 8 H+ (aq) + 5 e− Reduction: 2 e− + 6 H+ + BiO3− (s) → Bi3+ (aq) + 3 H2O (l) The reaction is balanced by scaling the two half-cell reactions to involve the same number of electrons (multiplying the oxidation reaction by the number of electrons in the reduction step and vice versa): 8 H2O (l) + 2 Mn2+ (aq) → 2 MnO4− (aq) + 16 H+ (aq) + 10 e− 10 e− + 30 H+ + 5 BiO3− (s) → 5 Bi3+ (aq) + 15 H2O (l) Adding these two reactions eliminates the electrons terms and yields the balanced reaction: 14 H+ (aq) + 2 Mn2+ (aq) + 5 NaBiO3 (s) → 7 H2O (l) + 2 MnO4− (aq) + 5 Bi3+ (aq) + 5 Na+ (aq)

Basic media In basic media, OH− ions and water are added to half reactions to balance the overall reaction. For example, in the reaction between potassium permanganate and sodium sulfite: Unbalanced reaction: KMnO4 + Na2SO3 + H2O → MnO2 + Na2SO4 + KOH Reduction: 3 e− + 2 H2O + MnO4− → MnO2 + 4 OH− Oxidation: 2 OH− + SO32− → SO42− + H2O + 2 e− Balancing the number of electrons in the two half-cell reactions gives: 6 e− + 4 H2O + 2 MnO4− → 2 MnO2 + 8 OH− 6 OH− + 3 SO32− → 3 SO42− + 3 H2O + 6 e− Adding these two half-cell reactions together gives the balanced equation: 2 KMnO4 + 3 Na2SO3 + H2O → 2 MnO2 + 3 Na2SO4 + 2 KOH

See also • • • • • • • •

Organic redox reaction Hydrogenation Bessemer process Bioremediation Calvin cycle Citric acid cycle Electrochemical cell Electrochemistry

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Chemical looping combustion

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Electrochemical series Galvanic cell Membrane potential Oxidative addition and reductive elimination Reducing agent Thermic reaction Partial oxidation Reduction potential Chemical equation

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Reduced gas

References 1. ^ Hudlický, Miloš (1996). Reductions in Organic Chemistry. Washington, D.C.:

American Chemical Society. pp. 429. ISBN 0-8412-3344-6. 2. ^ Hudlický, Miloš (1990). Oxidations in Organic Chemistry. Washington, D.C.: American Chemical Society. pp. 456. ISBN 0-8412-1780-7. 3. ^ "gutier.doc". http://www.bioscience.org/2000/v5/d/gutier/gutier.pdf. Retrieved 200806-30.PDF (2.76 MiB) •

Schüring, J., Schulz, H. D., Fischer, W. R., Böttcher, J., Duijnisveld, W. H. (editors) (1999). Redox: Fundamentals, Processes and Applications, Springer-Verlag, Heidelberg, 246 pp. ISBN 978-3540665281 (pdf 3,6 MB)

External links Wikibooks has a book on the topic of General Chemistry/Redox Reactions Wikimedia Commons has media related to: Redox reactions • • • • • •

Chemical Equation Balancer - An open source chemical equation balancer that handles redox reactions. Video - Synthesis of Copper(II) Acetate 20 Feb. 2009 UC Berkeley video lecture on redox reactions Redox reactions calculator Redox reactions at Chemguide Online redox reaction equation balancer, balances equations of any half-cell and full reactions

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Examples of redox reaction? Read answer... Redox reaction involves the transfer of? Read answer... What is an oxidation-reduction or redox reaction? Read answer... Help us answer these What are redox titrations? What are not redox reaction? Do you have a picture of a Redox readtion of lithium? Sponsored Links EnSys Energy Consulting Downstream oil consultants, Refining Spreads, Refining Studies ensysenergy.com Home > Library > Literature & Language > WordNet Note: click on a word meaning below to see its connections and related words.

The noun has one meaning: Meaning #1: the conversion of a compound into an isomer of itself Synonym: isomerization

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Browse: Unanswered questions | New questions | New answers | Reference library 5min Related Video: Isomerisation

Top Wikipedia: Isomerisation Home > Library > Miscellaneous > Wikipedia In chemistry isomerisation is the process by which one molecule is transformed into another molecule which has exactly the same atoms, but the atoms are rearranged e.g. A-B-C → B-A-C (these related molecules are known as isomers [1]). In some molecules and under some conditions, isomerisation occurs spontaneously. Many isomers are equal or roughly equal in bond energy, and so exist in roughly equal amounts, provided that they can interconvert

relatively freely, that is the energy barrier between the two isomers is not too high. When the isomerisation occurs intramolecularly it is considered a rearrangement reaction.

Instances of Isomerization •

Isomerisations in hydrocarbon cracking. This is usually employed in organic chemistry, where fuels, such as pentane, a straight-chain isomer, are heated in the presence of a platinum catalyst. The resulting mixture of straight- and branched-chain isomers then have to be separated. An industrial process is also the isomerisation of n-butane into isobutane.

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Trans-cis isomerism. In certain compounds an interconversion of cis and trans isomers can be observed, for instance, with maleic acid and with azobenzene often by photoisomerization. An example is the photochemical conversion of the trans isomer to the cis isomer of resveratrol [2]:

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Aldose-ketose isomerism in biochemistry. Isomerisations between conformational isomers. These take place without an actual rearrangement for instance inconversion of two cyclohexane conformations Fluxional molecules display rapid interconversion of isomers e.g. Bullvalene.

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The energy difference between two isomers is called isomerisation energy. Isomerisations with low energy difference both experimental and computational (in parentheses) are endothermic trans-cis isomerisation of 2-butene with 2.6 (1.2) kcal/mol, cracking of isopentane to n-pentane with 3.6 (4.0) kcal/mol or conversion of trans-2-butene to 1-butene with 2.6 (2.4) kcal/mol.[3]

References 1. ^ Gold Book definition: Link

2. ^ Resveratrol Photoisomerization: An Integrative Guided-Inquiry Experiment Elyse

Bernard, Philip Britz-McKibbin, Nicholas Gernigon Vol. 84 No. 7 July 2007 Journal of Chemical Education 1159 3. ^ How to Compute Isomerization Energies of Organic Molecules with Quantum Chemical Methods Stefan Grimme, Marc Steinmetz, and Martin Korth J. Org. Chem.; 2007; 72(6) pp 2118 - 2126; (Article) doi:10.1021/jo062446p

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Help us answer these What are the seven branched alkanes of heptane isomerisation? Why is purpose of glucose 6-phosphate isomerisation in glycolysis? What is isomerisation? Post a question - any question - to the WikiAnswers Carbon dioxide Home > Library > Science > Sci-Tech Encyclopedia A colorless, odorless, tasteless gas, formula CO2, about 1.5 times as heavy as air. Under normal conditions, it is stable, inert, and nontoxic. The decay (slow oxidation) of all organic materials produces CO2. Fresh air contains approximately 0.033% CO2 by volume. In the respiratory action (breathing) of all animals and humans, CO2 is exhaled. Carbon dioxide gas may be liquefied or solidified. Solid CO2 is known as dry ice. Carbon dioxide is obtained commercially from four sources: gas wells, fermentation, combustion of carbonaceous fuels, and as a by-product of chemical processing. Applications include use as a

refrigerant, in either solid or liquid form, inerting medium, chemical reactant, neutralizing agent for alkalies, and pressurizing agent. Most CO2 is obtained as a by-product from steam-hydrocarbon reformers used in the production of ammonia, gasoline, and other chemicals; other sources include fermentation, deep gas wells, and direct production from carbonaceous fuels. Whatever the source, the crude CO2 (containing at least 90% CO2) is compressed in either two or three stages, cooled, purified, condensed to the liquid phase, and placed in insulated storage vessels. Carbon dioxide is distributed in three ways; in high-pressure uninsulated steel cylinders; as a low-pressure liquid in insulated truck trailers or rail tank cars; and as dry ice in insulated boxes, trucks, or boxcars. World of the Body: carbon dioxide Top Sponsored Links Graphite products Great Carbon provides high quality graphite products. www.gcarbon.com.tw Home > Library > Health > World of the Body When the body ‘burns’ food the end products are mainly water and carbon dioxide, together with some nitrogenous chemicals such as urea. The carbon dioxide enters the bloodstream, is carried to the lungs, and is excreted in the expired air of breathing. The atmospheric air we inhale contains virtually no carbon dioxide, whereas there is about 5% in the air we breathe out. Carbon dioxide reacts in the blood to form carbonic acid and bicarbonate and, if it were allowed to accumulate, would cause acidosis. This condition is particularly harmful to the cells of the brain. Carbon dioxide diffuses into the liquid in the brain, the cerebrospinal fluid (CSF) ; any excess makes it more acid, and this in turn stimulates neural receptors in the brain stem that increase breathing. The result is that the carbon dioxide is blown off in the lungs and the acidity of the blood and brain are kept close to normal levels. Carbon dioxide is the main chemical stimulus to breathing, which is regulated primarily to keep blood and brain acidity at healthy values. If the carbon dioxide in the lungs increases by only 0.2%, from a normal level of about 5%, then breathing is doubled. Breathholding accumulates carbon dioxide in the body, which leads to an irrepressible desire to breathe (lack of oxygen is also a stimulus, but far weaker than carbon dioxide). Conversely, if we voluntarily hyperventilate, the level of carbon dioxide in the blood will decrease, and breathing may be inhibited until more carbon dioxide accumulates. Hyperventilation can have harmful effects because of the pronounced reduction in blood and CSF acidity. Since decreases in carbon dioxide and acidity constrict blood vessels, particularly in the brain, one effect is to reduce the blood supply to the brain. Carbon dioxide was identified, but not understood chemically, in about 1600 AD by van Helmont, who called it ‘gas sylvestre’, the gas produced by combustion. He showed that it would not support life. Later Joseph Black, who had a lifelong interest in chemistry and was Professor of Medicine in Glasgow from 1757 to 1766, called it ‘fixed acid’, because it was absorbed by lime solution, and he showed that it was produced in respiration. The story goes that in 1764 Black climbed to the ceiling of a church in Glasgow, occupied for 10 hours of religious devotions by a

congregation of 1500, and measured the ‘fixed acid’ that was exhaled by the diligent and sleepy congregation. But it was Lavoisier (1743-94) who definitely established the excretion of carbon dioxide after its formation in metabolism, although he erroneously believed that it was formed in the lungs. Lavoisier was guillotined, and it was said that ‘it took but a second to cut off his head; a hundred years will not suffice to produce one like it.’ Lavoisier concluded that any series of lectures in an auditorium extending over 3 hours would leave the audience in a soporific state due to the accumulation of carbon dioxide. In theory he was right. Carbon dioxide in excess can act as an anaesthetic and, in animals, major surgery has been performed under its influence alone. Some human lung diseases such as chronic bronchitis may leave the patient drowsy or even comatose because of the build up of carbon dioxide in the body. It is claimed, probably incorrectly, that in social environments yawning and weariness are due to an accumulation of carbon dioxide. Van Helmont investigated a Grotto del Cane (cave of dogs) in Italy in which it was claimed, rather implausibly, that a tall dog owner would survive while his lowly dog would perish, due to the depressant effect of carbon dioxide, held to the ground because of its greater density than air. Perhaps Black's Glasgow congregation was fortunate. — John Widdicombe See also acid-base homeostasis; blood; respiration. Dental Dictionary: carbon dioxide Top Home > Library > Health > Dental Dictionary n A colorless, odorless gas produced by the complete oxidation of carbon. Carbon dioxide is a product of cell respiration and is carried by the blood to the lungs and exhaled. The acid-base balance of body fluids and tissues is affected by the level of carbon dioxide and its carbonate compounds. Britannica Concise Encyclopedia: carbon dioxide Top Home > Library > Miscellaneous > Britannica Concise Encyclopedia Inorganic compound, a colourless gas with a faint, sharp odour and a sour taste when dissolved in water, chemical formula CO2. Constituting about 0.03% of air by volume, it is produced when carbon-containing materials burn completely, and it is a product of fermentation and animal respiration. Plants use CO2 in photosynthesis to make carbohydrates. CO2 in Earth's atmosphere keeps some of the Sun's energy from radiating back into space (see greenhouse effect). In water, CO2 forms a solution of a weak acid, carbonic acid (H2CO3). The reaction of CO2 and ammonia is the first step in synthesizing urea. An important industrial material, CO2 is recovered from sources including flue gases, limekilns, and the process that prepares hydrogen for synthesis of ammonia. It is used as a refrigerant, a chemical intermediate, and an inert atmosphere; in fire

extinguishers, foam rubber and plastics, carbonated beverages (see carbonation), and aerosol sprays; in water treatment, welding, and cloud seeding; and for promoting plant growth in greenhouses. Under pressure it becomes a liquid, the form most often used in industry. If the liquid is allowed to expand, it cools and partially freezes to the solid form, dry ice. For more information on carbon dioxide, visit Britannica.com. Sports Science and Medicine: carbon dioxide Top Home > Library > Health > Sports Science and Medicine A colourless gas which makes up about 0.04% of the atmosphere. It is denser than air. It is toxic only above about 6% concentration, but it does not support respiration or combustion. It is excreted as a waste product of aerobic metabolism, and is carried to the veins, mainly as hydrogen carbonate (bicarbonate) ions. Expired air contains about 4% carbon dioxide. Increases in carbon dioxide levels stimulate the vasomotor centre to increase the ventilation rate so that more carbon dioxide can be eliminated from the lungs. Columbia Encyclopedia: carbon dioxide Top Home > Library > Miscellaneous > Columbia Encyclopedia carbon dioxide, chemical compound, CO2, a colorless, odorless, tasteless gas that is about one and one-half times as dense as air under ordinary conditions of temperature and pressure. It does not burn, and under normal conditions it is stable, inert and nontoxic. It will however support combustion of magnesium to give magnesium oxide and carbon. Although it is not a poison, it can cause death by suffocation if inhaled in large amounts. It is a fairly stable compound but decomposes at very high temperatures into carbon and oxygen. It is fairly soluble in water, one volume of it dissolving in an equal volume of water at room temperature and pressure; the resultant weakly acidic aqueous solution is called carbonic acid. The gas is easily liquefied by compression and cooling. If liquid carbon dioxide is quickly decompressed it rapidly expands and some of it evaporates, removing enough heat so that the rest of it cools into solid carbon dioxide "snow." A standard test for the presence of carbon dioxide is its reaction with limewater (a saturated water solution of calcium hydroxide) to form a milky-white precipitate of calcium hydroxide. Carbon dioxide occurs in nature both free and in combination (e.g., in carbonates). It is part of the atmosphere, making up about 1% of the volume of dry air. Because it is a product of combustion of carbonaceous fuels (e.g., coal, coke, fuel oil, gasoline, and cooking gas), there is usually more of it in city air than in country air. The natural balance of carbon dioxide in the atmosphere is growing from its stable level of 0.13% to a predicted 0.14% by the year 2000. It is anticipated that this extra carbon dioxide will fuel the greenhouse effect, warm the atmosphere, and further disrupt the natural carbon dioxide cycle (see global warming).

In various parts of the world-notably in Italy, Java, and Yellowstone National Park in the United States-carbon dioxide is formed underground and issues from fissures in the earth. Natural mineral waters such as Vichy water sparkle (effervesce) because excess carbon dioxide that dissolved in them under pressure collects in bubbles and escapes when the pressure is released. The chokedamp (see damp) of mines, pits, and old, unused wells is largely carbon dioxide. Carbon dioxide is a raw material for photosynthesis in green plants and is a product of animal respiration. It is also a product of the decay of organic matter. Carbon dioxide has varied commercial uses. Its greatest use as a chemical is in the production of carbonated beverages; it provides the sparkle in carbonated beverages such as soda water. Formed by the action of yeast or baking powder, carbon dioxide causes the rising of bread dough. The compound is also used in water softening, in the manufacture of aspirin and lead paint pigments, and in the Solvay process for the preparation of sodium carbonate. In some fire extinguishers carbon dioxide is expelled through a nozzle and settles on the flame, smothering it. It also has numerous nonchemical uses. It is used as a pressurizing medium and propellant, e.g., in aerosol cans of food, in fire extinguishers, in target pistols, and for inflating life rafts. Because it is relatively inert, it is used to provide a nonreactive atmosphere, e.g., for packaging foods, such as coffee, that can be spoiled by oxidation during storage. Solid carbon dioxide, known as dry ice, is used as a refrigerating agent. There are three principal commercial sources for carbon dioxide. High-purity carbon dioxide is produced from some wells. The gas is obtained as a byproduct of chemical manufacture, as in the fermentation of grain to make alcohol and the burning of limestone to make lime. It is also manufactured directly by burning carbonaceous fuels. For commercial use it is available as a liquid under high pressure in steel cylinders, as a low-temperature liquid at lower pressures, and as the solid dry ice. Wine Lover's Companion: carbon dioxide Top Home > Library > Food & Cooking > Wine Lover's Companion A colorless, odorless, incombustible gas. Carbon dioxide (CO2) is one of the two by-products of FERMENTATION, the other being ALCOHOL. Yeast acts on the natural grape sugar and converts 40 to 45 percent of it to carbon dioxide, which in most cases escapes into the air. In the production of SPARKLING WINES, however, carbon dioxide is purposely trapped in the wine to create effervescence. Science Dictionary: carbon dioxide Top Home > Library > Science > Science Dictionary A compound made up of molecules containing one carbon atom and two oxygen atoms.

 Carbon dioxide is normally found as a gas that is breathed out by animals and absorbed by green plants. The plants, in turn, return oxygen to the atmosphere. (See carbon cycle and respiration.)  Carbon dioxide is also given off in the burning of fossil fuels (see greenhouse effect). Veterinary Dictionary: carbon dioxide Top Home > Library > Animal Life > Veterinary Dictionary An odorless, colorless gas, CO2, resulting from oxidation of carbons, formed in the tissues and eliminated by the lungs; used with oxygen to stimulate respiration and in solid form (carbon dioxide snow—see below) as an escharotic, as a gas to euthanize laboratory rabbits and rodents. • • • • • •

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c. d. anesthesia — exposure of pigs for 45 seconds in a mixture of 60 to 70% CO2 in air is an adequate pre-slaughter anesthetic for pigs. c. d. combining power — the ability of blood plasma to combine with carbon dioxide; indicative of the alkali reserve and a measure of the acid–base balance of the blood. c. d. content — the amount of carbonic acid and bicarbonate in the blood; reported in millimoles per liter. c. d. dissociation curve — a graph demonstrating the relationship between the blood content of CO2 and the Pco2. c. d. narcosis — respiratory acidosis. c. d. snow — solid carbon dioxide, formed by rapid evaporation of liquid carbon dioxide; it gives a temperature of about −110°F (−79°C), and is used as an escharotic in various skin diseases. Called also dry ice. c. d. tension — the partial pressure of carbon dioxide in the blood; noted as Pco2 in blood gas analysis. See also respiration. c. d. transport — carbon dioxide passes from tissues to blood by diffusion, in the blood by solution and via reactions within plasma and erythrocytes, from blood to pulmonary alveoli by diffusion.

Cosmic Lexicon: Carbon dioxide Top Home > Library > Science > Cosmic Lexicon A compound formed by combining one carbon atom with two oxygen atoms, making the molecule CO2. Carbon dioxide is an important part of the atmospheres of Venus and Mars. Carbon dioxide gas condenses to a solid below -78o C. This solid is commonly known as dry ice. The polar ice caps on Mars are made of frozen water and carbon dioxide. Wikipedia: Carbon dioxide Top Home > Library > Miscellaneous > Wikipedia

"CO2" redirects here. For the postal district, see CO postcode area.

Carbon dioxide

IUPAC name Other names CAS number PubChem EC number UN number RTECS number SMILES InChI ChemSpider ID Molecular formula Molar mass Appearance Density

Carbon dioxide Carbonic acid gas; carbonic anhydride; dry ice (solid) Identifiers 124-38-9 280 204-696-9 1013 Solid (dry ice): 1845 Mixtures with Ethylene oxide: 1952,3300 FF6400000 C(=O)=O 1/CO2/c2-1-3

274 Properties CO2 44.010 g mol-1 colorless, odorless gas 1.562 g mL-1 (solid at 1 atm and −78.5 °C) 0.770 g mL-1 (liquid at 56 atm and 20 °C) 1.977 g L-1 (gas at 1 atm and 0 °C) 849.6 g L-1 (supercritical fluid at 150 atm and 30 °C

Melting point

-78 °C, 194.7 K, -109 °F (subl.) -57 °C, 216.6 K, -70 °F ((at Boiling point 5.185 bar)) Solubility in water 1.45 g L-1 at 25 °C, 100 kPa Acidity (pKa) 6.35, 10.33 Refractive index (nD) 1.1120 Viscosity 0.07 cP at −78 °C Dipole moment zero Structure Molecular shape linear Related compounds Other anions Carbon disulfide Silicon dioxide Germanium dioxide Other cations Tin dioxide Lead dioxide

Carbon monoxide Carbon suboxide Related carbon oxides Dicarbon monoxide Carbon trioxide Carbonic acid Related compounds Carbonyl sulfide Supplementary data page Structure and n, εr, etc. properties Thermodynamic Phase behaviour data Solid, liquid, gas Spectral data UV, IR, NMR, MS (what is this?) (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

Carbon dioxide (chemical formula: CO2) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state. Carbon dioxide is used by plants during photosynthesis to make sugars, which may either be consumed in respiration or used as the raw material to produce other organic compounds needed for plant growth and development. It is produced during respiration by plants, and by all animals, fungi and microorganisms that depend either directly or indirectly on plants for food. It is thus a major component of the carbon cycle. Carbon dioxide is generated as a by-product of the combustion of fossil fuels or the burning of vegetable matter, among other chemical processes. Small amounts of carbon dioxide are emitted from volcanoes and other geothermal processes such as hot springs and geysers and by the dissolution of carbonates in crustal rocks. As of March 2009, carbon dioxide in the Earth's atmosphere is at a concentration of 387 ppm by volume.[1] Atmospheric concentrations of carbon dioxide fluctuate slightly with the change of the seasons, driven primarily by seasonal plant growth in the Northern Hemisphere. Concentrations of carbon dioxide fall during the northern spring and summer as plants consume the gas, and rise during the northern autumn and winter as plants go dormant, die and decay. Carbon dioxide is a greenhouse gas as it transmits visible light but absorbs strongly in the infrared and near-infrared. Carbon dioxide has no liquid state at pressures below 5.1 atmospheres. At 1 atmosphere (near mean sea level pressure), the gas deposits directly to a solid at temperatures below −78 °C and the solid sublimes directly to a gas above −78 °C. In its solid state, carbon dioxide is commonly called dry ice. CO2 is an acidic oxide: an aqueous solution turns litmus from blue to pink. It is the anhydride of carbonic acid, an acid which is unstable and is known to exist only in aqueous solution. CO2 + H2O

H2CO3

CO2 is toxic in higher concentrations: 1% (10,000 ppm) will make some people feel drowsy.[2] Concentrations of 7% to 10% cause dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour.[3]

Contents [hide]

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1 Chemical and physical properties 2 History of human understanding 3 Isolation and production o 3.1 Industrial production 4 Uses o 4.1 Drinks o 4.2 Foods o 4.3 Pneumatic systems o 4.4 Fire extinguisher o 4.5 Welding o 4.6 Caffeine removal o 4.7 Pharmaceutical and other chemical processing o 4.8 Agricultural / Biological applications o 4.9 Lasers o 4.10 Polymers and plastics o 4.11 Oil recovery o 4.12 As refrigerants o 4.13 Coal bed methane recovery o 4.14 Wine making o 4.15 pH control 5 In the Earth's atmosphere 6 In the oceans 7 Biological role o 7.1 Role in photosynthesis o 7.2 Toxicity o 7.3 Human physiology 8 See also 9 References 10 Further reading

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11 External links

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• • •

Chemical and physical properties

Carbon dioxide pressure-temperature phase diagram showing the triple point and critical point of carbon dioxide

Small pellets of dry ice subliming in air. For more details on this topic, see Carbon dioxide (data page). Carbon dioxide is colorless. At low concentrations, the gas is odorless. At higher concentrations it has a sharp, acidic odor. It will act as an asphyxiant and an irritant. When inhaled at concentrations much higher than usual atmospheric levels, it can produce a sour taste in the mouth and a stinging sensation in the nose and throat. These effects result from the gas dissolving in the mucous membranes and saliva, forming a weak solution of carbonic acid. This sensation can also occur during an attempt to stifle a burp after drinking a carbonated beverage. Amounts above 5,000 ppm are considered very unhealthy, and those above about 50,000 ppm (equal to 5% by volume) are considered dangerous to animal life.[4] At standard temperature and pressure, the density of carbon dioxide is around 1.98 kg/m³, about 1.5 times that of air. The carbon dioxide molecule (O=C=O) contains two double bonds and has a linear shape. It has no electrical dipole, and as it is fully oxidized, it is moderately reactive and is non-flammable, but will support the combustion of metals such as magnesium. At −78.51° C or −109.3° F, carbon dioxide changes directly from a solid phase to a gaseous phase through sublimation, or from gaseous to solid through deposition. Solid carbon dioxide is normally called "dry ice", a generic trademark. It was first observed in 1825 by the French chemist Charles Thilorier. Dry ice is commonly used as a cooling agent, and it is relatively inexpensive. A convenient property for this purpose is that solid carbon dioxide sublimes directly

into the gas phase leaving no liquid. It can often be found in grocery stores and laboratories, and it is also used in the shipping industry. The largest non-cooling use for dry ice is blast cleaning. Liquid carbon dioxide forms only at pressures above 5.1 atm; the triple point of carbon dioxide is about 518 kPa at −56.6 °C (See phase diagram, above). The critical point is 7.38 MPa at 31.1 °C. [5]

An alternative form of solid carbon dioxide, an amorphous glass-like form, is possible, although not at atmospheric pressure.[6] This form of glass, called carbonia, was produced by supercooling heated CO2 at extreme pressure (40–48 GPa or about 400,000 atmospheres) in a diamond anvil. This discovery confirmed the theory that carbon dioxide could exist in a glass state similar to other members of its elemental family, like silicon (silica glass) and germanium. Unlike silica and germania glasses, however, carbonia glass is not stable at normal pressures and reverts back to gas when pressure is released. See also: Supercritical carbon dioxide, dry ice, and MO diagram

History of human understanding

Crystal structure of dry ice Carbon dioxide was one of the first gases to be described as a substance distinct from air. In the seventeenth century, the Flemish chemist Jan Baptist van Helmont observed that when he burned charcoal in a closed vessel, the mass of the resulting ash was much less than that of the original charcoal. His interpretation was that the rest of the charcoal had been transmuted into an invisible substance he termed a "gas" or "wild spirit" (spiritus sylvestre). The properties of carbon dioxide were studied more thoroughly in the 1750s by the Scottish physician Joseph Black. He found that limestone (calcium carbonate) could be heated or treated with acids to yield a gas he called "fixed air." He observed that the fixed air was denser than air and did not support either flame or animal life. Black also found that when bubbled through an aqueous solution of lime (calcium hydroxide), it would precipitate calcium carbonate. He used this phenomenon to illustrate that carbon dioxide is produced by animal respiration and microbial fermentation. In 1772, English chemist Joseph Priestley published a paper entitled

Impregnating Water with Fixed Air in which he described a process of dripping sulfuric acid (or oil of vitriol as Priestley knew it) on chalk in order to produce carbon dioxide, and forcing the gas to dissolve by agitating a bowl of water in contact with the gas.[7] Carbon dioxide was first liquefied (at elevated pressures) in 1823 by Humphry Davy and Michael Faraday.[8] The earliest description of solid carbon dioxide was given by Charles Thilorier, who in 1834 opened a pressurized container of liquid carbon dioxide, only to find that the cooling produced by the rapid evaporation of the liquid yielded a "snow" of solid CO2.[9]

Isolation and production Carbon dioxide may be obtained from air distillation. However, this yields only very small quantities of CO2. A large variety of chemical reactions yield carbon dioxide, such as the reaction between most acids and most metal carbonates. For example, the reaction between hydrochloric acid and calcium carbonate (limestone or chalk) is depicted below: 2 HCl + CaCO3 → CaCl2 + H2CO3 The H2CO3 then decomposes to water and CO2. Such reactions are accompanied by foaming or bubbling, or both. In industry such reactions are widespread because they can be used to neutralize waste acid streams. The production of quicklime (CaO) a chemical that has widespread use, from limestone by heating at about 850 °C also produces CO2: CaCO3 → CaO + CO2 The combustion of all carbon containing fuels, such as methane (natural gas), petroleum distillates (gasoline, diesel, kerosene, propane), but also of coal and wood, will yield carbon dioxide and, in most cases, water. As an example the chemical reaction between methane and oxygen is given below. CH4 + 2 O2 → CO2 + 2 H2O Iron is reduced from its oxides with coke in a blast furnace, producing pig iron and carbon dioxide: 2 Fe2O3 + 3 C → 4 Fe + 3 CO2 Yeast metabolizes sugar to produce carbon dioxide and ethanol, also known as alcohol, in the production of wines, beers and other spirits, but also in the production of bioethanol: C6H12O6 → 2 CO2 + 2 C2H5OH All aerobic organisms produce CO2 when they oxidize carbohydrates, fatty acids, and proteins in the mitochondria of cells. The large number of reactions involved are exceedingly complex and

not described easily. Refer to (cellular respiration, anaerobic respiration and photosynthesis). Photoautotrophs (i.e. plants, cyanobacteria) use another modus operandi: Plants absorb CO2 from the air, and, together with water, react it to form carbohydrates: nCO2 + nH2O → (CH2O)n + nO2 Carbon dioxide is soluble in water, in which it spontaneously interconverts between CO2 and H2CO3 (carbonic acid). The relative concentrations of CO2, H2CO3, and the deprotonated forms HCO−3 (bicarbonate) and CO2−3(carbonate) depend on the pH. In neutral or slightly alkaline water (pH > 6.5), the bicarbonate form predominates (>50%) becoming the most prevalent (>95%) at the pH of seawater, while in very alkaline water (pH > 10.4) the predominant (>50%) form is carbonate. The bicarbonate and carbonate forms are very soluble, such that airequilibrated ocean water (mildly alkaline with typical pH = 8.2 – 8.5) contains about 120 mg of bicarbonate per liter.

Industrial production Carbon dioxide is produced mainly from six processes:[10] 1. From combustion of fossil fuels and wood; 2. As a by-product of hydrogen production plants, where methane is converted to CO2; 3. As a by-product of fermentation of sugar in the brewing of beer, whisky and other

alcoholic beverages; 4. From thermal decomposition of limestone, CaCO3, in the manufacture of lime, CaO; 5. As a by-product of sodium phosphate manufacture; 6. Directly from natural carbon dioxide springs, where it is produced by the action of

acidified water on limestone or dolomite.

Uses

Carbon dioxide bubbles in a soft drink. Carbon dioxide is used by the food industry, the oil industry, and the chemical industry.[10] It is used in many consumer products that require pressurized gas because it is inexpensive and nonflammable, and because it undergoes a phase transition from gas to liquid at room temperature at an attainable pressure of approximately 60 bar (870 psi, 59 atm), allowing far

more carbon dioxide to fit in a given container than otherwise would. Life jackets often contain canisters of pressured carbon dioxide for quick inflation. Aluminum capsules are also sold as supplies of compressed gas for airguns, paintball markers, for inflating bicycle tires, and for making seltzer. Rapid vaporization of liquid carbon dioxide is used for blasting in coal mines. High concentrations of carbon dioxide can also be used to kill pests, such as the Common Clothes Moth.

Drinks Carbon dioxide is used to produce carbonated soft drinks and soda water. Traditionally, the carbonation in beer and sparkling wine came about through natural fermentation, but many manufacturers carbonate these drinks artificially. In the case of bottled and kegged beer, artificial carbonation is now the most common method used. With the exception of British Real Ale, draught (draft) beer is usually transferred from kegs in a cold room or cellar to dispensing taps on the bar using pressurised carbon dioxide, often mixed with nitrogen.

Foods A candy called Pop Rocks is pressurized with carbon dioxide gas at about 40 bar (600 psi). When placed in the mouth, it dissolves (just like other hard candy) and releases the gas bubbles with an audible pop. Leavening agents produce carbon dioxide to cause dough to rise. Baker's yeast produces carbon dioxide by fermentation of sugars within the dough, while chemical leaveners such as baking powder and baking soda release carbon dioxide when heated or if exposed to acids.

Pneumatic systems Carbon dioxide is one of the most commonly used compressed gases for pneumatic (pressurized gas) systems in portable pressure tools and combat robots.

Fire extinguisher Carbon dioxide extinguishes flames, and some fire extinguishers, especially those designed for electrical fires, contain liquid carbon dioxide under pressure. Carbon dioxide has also been widely used as an extinguishing agent in fixed fire protection systems for total flooding of a protected space, (National Fire Protection Association Code 12). International Maritime Organisation standards also recognise carbon dioxide systems for fire protection of ship holds and engine rooms. Carbon dioxide based fire protection systems have been linked to several deaths. A review of CO2 systems (Carbon Dioxide as a Fire Suppressant: Examining the Risks, US EPA) identified 51 incidents between 1975 and the date of the report, causing 72 deaths and 145 injuries.

Welding

Carbon dioxide also finds use as an atmosphere for welding, although in the welding arc, it reacts to oxidize most metals. Use in the automotive industry is common despite significant evidence that welds made in carbon dioxide are more brittle than those made in more inert atmospheres, and that such weld joints deteriorate over time because of the formation of carbonic acid. It is used as a welding gas primarily because it is much less expensive than more inert gases such as argon or helium.

Caffeine removal Liquid carbon dioxide is a good solvent for many lipophilic organic compounds, and is used to remove caffeine from coffee. First, the green coffee beans are soaked in water. The beans are placed in the top of a column seventy feet (21 m) high. Then supercritical carbon dioxide in fluid form at about 93 degrees Celsius enters at the bottom of the column. The caffeine diffuses out of the beans and into the carbon dioxide

Pharmaceutical and other chemical processing Carbon dioxide has begun to attract attention in the pharmaceutical and other chemical processing industries as a less toxic alternative to more traditional solvents such as organochlorides. It's used by some dry cleaners for this reason. (See green chemistry.) In the chemical industry, carbon dioxide is used for the production of urea, carbonates and bicarbonates, and sodium salicylate.

Agricultural / Biological applications Plants require carbon dioxide to conduct photosynthesis. Greenhouses may (and of large size must) enrich their atmospheres with additional CO2 to sustain plant life and growth. A photosynthesis-related drop (by a factor less than two) in carbon dioxide concentration in a greenhouse compartment would kill green plants, or, at least, completely stop their growth. At very high concentrations (a factor of 100 or more higher than its atmospheric concentration), carbon dioxide can be toxic to animal life, so raising the concentration to 10,000 ppm (1%) or higher for several hours will eliminate pests such as whiteflies and spider mites in a greenhouse. It has been proposed that carbon dioxide from power generation be bubbled into ponds to grow algae that could then be converted into biodiesel fuel.[11] Carbon dioxide is already increasingly used in greenhouses as the main carbon source for Spirulina algae. In medicine, up to 5% carbon dioxide (130 times the atmospheric concentration) is added to pure oxygen for stimulation of breathing after apnea and to stabilize the O2/CO2 balance in blood.

Lasers

A carbon dioxide laser. A common type of industrial gas laser is the carbon dioxide laser.

Polymers and plastics Carbon dioxide can also be combined with limonene oxide from orange peels or other epoxides to create polymers and plastics.[12]

Oil recovery Carbon dioxide is used in enhanced oil recovery where it is injected into or adjacent to producing oil wells, usually under supercritical conditions. It acts as both a pressurizing agent and, when dissolved into the underground crude oil, significantly reduces its viscosity, enabling the oil to flow more rapidly through the earth to the removal well.[13] In mature oil fields, extensive pipe networks are used to carry the carbon dioxide to the injection points.

As refrigerants Liquid and solid carbon dioxide are important refrigerants, especially in the food industry, where they are employed during the transportation and storage of ice cream and other frozen foods. Solid carbon dioxide is called "dry ice" and is used for small shipments where refrigeration equipment is not practical. Liquid carbon dioxide (industry nomenclature R744 or R-744) was used as a refrigerant prior to the discovery of R-12 and is likely to enjoy a renaissance due to environmental concerns. Its physical properties are highly favorable for cooling, refrigeration, and heating purposes, having a high volumetric cooling capacity. Due to its operation at pressures of up to 130 bars, CO2 systems require highly resistant components that have already been developed for mass production in many sectors. In automobile air conditioning, in more than 90% of all driving conditions for latitudes higher than 50°, R744 operates more efficiently than systems using R134a. Its environmental advantages (GWP of 1, non-ozone depleting, non-toxic, non-flammable) could make it the future working fluid to replace current HFCs in cars, supermarkets, hot water heat pumps, among others. Some applications: Coca-Cola has fielded CO2-based beverage coolers and the U.S. Army is interested in CO2 refrigeration and heating technology.[14][15]

By the end of 2007, the global automobile industry is expected to decide on the next-generation refrigerant in car air conditioning. CO2 is one discussed option.(see The Cool War)

Coal bed methane recovery In enhanced coal bed methane recovery, carbon dioxide is pumped into the coal seam to displace methane.[16]

Wine making Carbon dioxide in the form of dry ice is often used in the wine making process to cool down bunches of grapes quickly after picking to help prevent spontaneous fermentation by wild yeasts. The main advantage of using dry ice over regular water ice is that it cools the grapes without adding any additional water that may decrease the sugar concentration in the grape must, and therefore also decrease the alcohol concentration in the finished wine. Dry ice is also used during the cold soak phase of the wine making process to keep grapes cool. The carbon dioxide gas that results from the sublimation of the dry ice tends to settle to the bottom of tanks because it is heavier than regular air. The settled carbon dioxide gas creates an hypoxic environment which helps to prevent bacteria from growing on the grapes until it is time to start the fermentation with the desired strain of yeast. Carbon dioxide is also used to create a hypoxic environment for carbonic maceration, the process used to produce Beaujolais wine. Carbon dioxide is sometimes used to top up wine bottles or other storage vessels such as barrels to prevent oxidation, though it has the problem that it can dissolve into the wine, making a previously still wine slightly fizzy. For this reason, other gasses such as nitrogen or argon are preferred for this process by professional wine makers.

pH control Carbon dioxide can be used as a mean of controlling the pH of swimming pools, by continuously adding gas to the water, thus keeping the pH level from rising. Among the advantages of this is the avoidance of handling (more hazardous) acids.

In the Earth's atmosphere

The Keeling Curve of atmospheric CO2 concentrations measured at Mauna Loa Observatory. Main article: Carbon dioxide in the Earth's atmosphere Carbon dioxide in earth's atmosphere is considered a trace gas currently occurring at an average concentration of about 385 parts per million by volume or 582 parts per million by mass. The total mass of atmospheric carbon dioxide is 3.0×1015 kg (3,000 gigatonnes). Its concentration varies seasonally (see graph at right) and also considerably on a regional basis, especially near the ground. In urban areas concentrations are generally higher and indoors they can reach 10 times background levels. Carbon dioxide is a greenhouse gas.

Yearly increase of atmospheric CO2: In the 1960s, the average annual increase was 37% of the 2000-2007 average.[17] Five hundred million years ago carbon dioxide was 20 times more prevalent than today, decreasing to 4-5 times during the Jurassic period and then slowly declining with a particularly swift reduction occurring 49 million years ago.[18][19] Human activities such as the combustion of fossil fuels and deforestation have caused the atmospheric concentration of carbon dioxide to increase by about 35% since the beginning of the age of industrialization.[20] Up to 40% of the gas emitted by some volcanoes during subaerial volcanic eruptions is carbon dioxide.[21] It is estimated that volcanoes release about 130-230 million tonnes (145-255 million tons) of CO2 into the atmosphere each year. This is about a factor of 1000 smaller than the sum of the other natural sources and about factor of about 100 smaller than the sources from human activity. Carbon dioxide is also produced by hot springs such as those at the Bossoleto site near Rapolano Terme in Tuscany, Italy. Here, in a bowl-shaped depression of about 100 m diameter, local concentrations of CO2 rise to above 75% overnight, sufficient to kill insects and small animals, but warm rapidly when sunlit and disperse by convection during the day.[22] Locally

high concentrations of CO2, produced by disturbance of deep lake water saturated with CO2 are thought to have caused 37 fatalities at Lake Monoun, Cameroon in 1984 and 1700 casualties at Lake Nyos, Cameroon in 1986.[23] Emissions of CO2 by human activities are currently more than 130 times greater than the quantity emitted by volcanoes, amounting to about 27 billion tonnes per year.[24]

In the oceans There is about 50 times as much carbon dissolved in the oceans in the form of CO2 and carbonic acid, bicarbonate and carbonate ions as exists in the atmosphere. The oceans act as an enormous carbon sink, and have taken up about a third of CO2 emitted by human activity.[25] Gas solubility decreases as the temperature of water increases and therefore the rate of uptake from the atmosphere decreases as ocean temperatures rise. Most of the CO2 taken up by the ocean forms carbonic acid in equilibrium with bicarbonate and carbonate ions. Some is consumed in photosynthesis by organisms in the water, and a small proportion of that sinks and leaves the carbon cycle. Increased CO2 in the atmosphere has led to decreasing alkalinity of seawater and there is some concern that this may adversely affect organisms living in the water. In particular, with decreasing alkalinity, the availability of carbonates for forming shells decreases.[26]

Biological role Carbon dioxide is an end product in organisms that obtain energy from breaking down sugars, fats and amino acids with oxygen as part of their metabolism, in a process known as cellular respiration. This includes all plants, animals, many fungi and some bacteria. In higher animals, the carbon dioxide travels in the blood from the body's tissues to the lungs where it is exhaled. In plants using photosynthesis, carbon dioxide is absorbed from the atmosphere.

Role in photosynthesis

Overview of photosynthesis and respiration. Carbon dioxide (at right), together with water, form oxygen and organic compounds (at left) by photosynthesis, which can be respired to water and (CO2). Plants remove carbon dioxide from the atmosphere by photosynthesis, also called carbon assimilation, which uses light energy to produce organic compounds (cellulose, lipids, and various proteins) by combining carbon dioxide and water. Free oxygen is released as gas from the decomposition of water molecules, while the hydrogen is split into its protons and electrons and used to generate chemical energy via photophosphorylation. This energy is required for the fixation of carbon dioxide in the Calvin cycle to make 3-phosphoglycerate that is used in metabolism, to construct sugars that can be used as an energy source within the plant through respiration and as the raw material for the construction of more complex organic molecules, such as polysaccharides, nucleic acids and proteins during growth. Even when greenhouses are vented, carbon dioxide must be introduced into them to maintain plant growth, as the concentration of carbon dioxide can fall during daylight hours to as low as 200 ppm (a limit of C3 carbon fixation photosynthesis[citation needed]). Plants can grow up to 50 percent faster in concentrations of 1,000 ppm CO2 when compared with ambient conditions, though this assumes no change in climate and no limitation on other nutrients.[27] Some people (for example David Bellamy) believe that as the concentration of CO2 rises in the atmosphere that it will lead to faster plant growth and therefore increase food production.[28] Such views are too simplistic; studies have shown that increased CO2 leads to fewer stomata developing on plants[29] which leads to reduced water usage.[30] Studies using FACE have shown that increases in CO2 lead to decreased concentration of micronutrients in crop plants.[31] This may have knockon effects on other parts of ecosystems as herbivores will need to eat more food to gain the same amount of protein.[32] Plants also emit CO2 during respiration, and so the majority of plants and algae, which use C3 photosynthesis, are only net absorbers during the day. Though a growing forest will absorb many tons of CO2 each year, the World Bank writes that a mature forest will produce as much CO2 from respiration and decomposition of dead specimens (e.g. fallen branches) as is used in biosynthesis in growing plants.[33] However six experts in biochemistry, biogeology, forestry and related areas writing in the science journal Nature that "Our results demonstrate that old-growth forests can continue to accumulate carbon, contrary to the long-standing view that they are carbon neutral." [34] Mature forests are valuable carbon sinks, helping maintain balance in the Earth's atmosphere. Additionally, and crucially to life on earth, photosynthesis by phytoplankton consumes dissolved CO2 in the upper ocean and thereby promotes the absorption of CO2 from the atmosphere.[35]

Toxicity See also: Carbon dioxide poisoning

Main symptoms of Carbon dioxide toxicity, by increasing volume percent in air.[2][36]. Carbon dioxide content in fresh air (averaged between sea-level and 10 hPa level, i.e. about 30 km altitude) varies between 0.036% (360 ppm) and 0.039% (390 ppm), depending on the location[37]. Prolonged exposure to moderate concentrations can cause acidosis and adverse effects on calcium phosphorus metabolism resulting in increased calcium deposits in soft tissue. Carbon dioxide is toxic to the heart and causes diminished contractile force.[36] Toxicity and its effects increase with the concentration of CO2, here given in volume percent of CO2 in the air: • • • •

1%, as can occur in a crowded auditorium with poor ventilation, can cause drowsiness with prolonged exposure.[2] At 2% it is mildly narcotic and causes increased blood pressure and pulse rate, and causes reduced hearing.[36] At about 5% it causes stimulation of the respiratory centre, dizziness, confusion and difficulty in breathing accompanied by headache and shortness of breath.[36] At about 8% it causes headache, sweating, dim vision, tremor and loss of consciousness after exposure for between five and ten minutes.[36]

A natural disaster linked to CO2 intoxication occurred during the limnic eruptions in the CO2-rich lakes of Monoun and Nyos in the Okun range of North-West Cameroon: the gas was brutally expelled from the mountain lakes and leaked into the surrounding valleys, killing most animal forms. During the Lake Nyos tragedy of 1988, 1700 villagers and 3500 livestock died. Due to the health risks associated with carbon dioxide exposure, the U.S. Occupational Safety and Health Administration says that average exposure for healthy adults during an eight-hour work day should not exceed 5,000 ppm (0.5%). The maximum safe level for infants, children, the elderly and individuals with cardio-pulmonary health issues is significantly less. For shortterm (under ten minutes) exposure, the U.S. National Institute for Occupational Safety and Health (NIOSH) and American Conference of Government Industrial Hygienists (ACGIH) limit

is 30,000 ppm (3%). NIOSH also states that carbon dioxide concentrations exceeding 4% are immediately dangerous to life and health.[38] Adaptation to increased levels of CO2 occurs in humans. Continuous inhalation of CO2 can be tolerated at three percent inspired concentrations for at least one month and four percent inspired concentrations for over a week. It was suggested that 2.0 percent inspired concentrations could be used for closed air spaces (e.g. a submarine) since the adaptation is physiological and reversible. Decrement in performance or in normal physical activity does not happen at this level.[39][40] These figures are valid for pure carbon dioxide. In indoor spaces occupied by people the carbon dioxide concentration will reach higher levels than in pure outdoor air. Concentrations higher than 1,000 ppm will cause discomfort in more than 20% of occupants, and the discomfort will increase with increasing CO2 concentration. The discomfort will be caused by various gases coming from human respiration and perspiration, and not by CO2 itself. At 2,000 ppm the majority of occupants will feel a significant degree of discomfort, and many will develop nausea and headaches. The CO2 concentration between 300 and 2,500 ppm is used as an indicator of indoor air quality. Acute carbon dioxide toxicity is sometimes known by the names given to it by miners: blackdamp (also called choke damp or stythe). Miners would try to alert themselves to dangerous levels of carbon dioxide in a mine shaft by bringing a caged canary with them as they worked. The canary would inevitably die before CO2 reached levels toxic to people. Carbon dioxide ppm levels (CDPL) are a surrogate for measuring indoor pollutants that may cause occupants to grow drowsy, get headaches, or function at lower activity levels. To eliminate most indoor air quality complaints, total indoor CDPL must be reduced to below 600. NIOSH considers that indoor air concentrations that exceed 1,000 are a marker suggesting inadequate ventilation. ASHRAE recommends they not exceed 1,000 inside a space.

Human physiology See also: Arterial blood gas CO2 is carried in blood in three different ways. (The exact percentages vary depending whether it is arterial or venous blood). •

• •

Most of it (about 70% – 80%) is converted to bicarbonate ions HCO−3 by the enzyme carbonic anhydrase in the red blood cells,[41] by the reaction CO2 + H2O → H2CO3 → H+ + HCO−3. 5% – 10% is dissolved in the plasma[41] 5% – 10% is bound to hemoglobin as carbamino compounds[41]

Hemoglobin, the main oxygen-carrying molecule in red blood cells, carries both oxygen and carbon dioxide. However, the CO2 bound to hemoglobin does not bind to the same site as oxygen. Instead, it combines with the N-terminal groups on the four globin chains. However,

because of allosteric effects on the hemoglobin molecule, the binding of CO2 decreases the amount of oxygen that is bound for a given partial pressure of oxygen. The decreased binding to carbon dioxide in the blood due to increased oxygen levels is known as the Haldane Effect, and is important in the transport of carbon dioxide from the tissues to the lungs. Conversely, a rise in the partial pressure of CO2 or a lower pH will cause offloading of oxygen from hemoglobin, which is known as the Bohr Effect. Carbon dioxide is one of the mediators of local autoregulation of blood supply. If its levels are high, the capillaries expand to allow a greater blood flow to that tissue. Bicarbonate ions are crucial for regulating blood pH. A person's breathing rate influences the level of CO2 in their blood. Breathing that is too slow or shallow causes respiratory acidosis, while breathing that is too rapid leads to hyperventilation, which can cause respiratory alkalosis. Although the body requires oxygen for metabolism, low oxygen levels do not stimulate breathing. Rather, breathing is stimulated by higher carbon dioxide levels. As a result, breathing low-pressure air or a gas mixture with no oxygen at all (such as pure nitrogen) can lead to loss of consciousness without ever experiencing air hunger. This is especially perilous for high-altitude fighter pilots. It is also why flight attendants instruct passengers, in case of loss of cabin pressure, to apply the oxygen mask to themselves first before helping others — otherwise one risks going unconscious.[41] Typically the gas we exhale is about 4% to 5% carbon dioxide and 4% to 5% less oxygen than was inhaled. Breathing produces approximately 2.3 pounds (1 kg) of carbon dioxide per day per person.[42]

See also • • • • • • • • • • • • • • • • •

Bosch reaction Carbogen Carbon cycle Carbon dioxide (data page) Carbon dioxide sensor Carbon dioxide sink Carbon monoxide Center for the Study of Carbon Dioxide and Global Change CO2 sequestration CO2 degassing in Lake Nyos Dry ice EcoCute - As refrigerants Emission standards Global warming Greenhouse gas Kaya identity Sabatier process

References 1. ^ Mauna Loa CO2 annual mean data from NOAA. "Trend" data was used. See also:

Trends in Carbon Dioxide from NOAA. 2. ^ a b c Toxicity of Carbon Dioxide Gas Exposure, CO2 Poisoning Symptoms, Carbon Dioxide Exposure Limits, and Links to Toxic Gas Testing Procedures By Daniel Friedman - InspectAPedia 3. ^ "Carbon Dioxide as a Fire Suppressant: Examining the Risks". U.S. Environmental Protection Agency:. http://www.epa.gov/ozone/snap/fire/co2/co2report.html. 4. ^ Staff (16 August 2006). "Carbon dioxide: IDLH Documentation". National Institute for Occupational Safety and Health. http://www.cdc.gov/niosh/idlh/124389.html. Retrieved 2007-07-05. 5. ^ "Phase change data for Carbon dioxide". National Institute of Standards and Technology. http://webbook.nist.gov/cgi/cbook.cgi? ID=C124389&Units=SI&Mask=4#Thermo-Phase. Retrieved 2008-01-21. 6. ^ Santoro, M.; et al. (2006). "Amorphous silica-like carbon dioxide". Nature 441: 857– 860. doi:10.1038/nature04879. 7. ^ Priestley, Joseph (1772). "Observations on Different Kinds of Air". Philosophical Transactions 62: 147–264. doi:10.1098/rstl.1772.0021. http://web.lemoyne.edu/~GIUNTA/priestley.html. 8. ^ Davy, Humphry (1823). "On the Application of Liquids Formed by the Condensation of Gases as Mechanical Agents" (PDF). Philosophical Transactions 113: 199–205. doi:10.1098/rstl.1823.0020. 9. ^ Duane, H.D. Roller; M. Thilorier (1952). "Thilorier and the First Solidification of a "Permanent" Gas (1835)". Isis 43 (2): 109–113. doi:10.1086/349402. 10. ^ a b Pierantozzi, Ronald (2001). "Carbon Dioxide". Kirk-Othmer Encyclopedia of Chemical Technology. Wiley. doi:10.1002/0471238961.0301180216090518.a01.pub2. 11. ^ Clayton, Mark (2006-01-11). "Algae - like a breath mint for smokestacks". Christian Science Monitor. http://www.csmonitor.com/2006/0111/p01s03-sten.html. Retrieved 2007-10-11. 12. ^ Davidson, Sarah (2005-01-17). "Sweet and environmentally beneficial discovery: Plastics made from orange peel and a greenhouse gas". Cornell News. http://www.news.cornell.edu/releases/Jan05/Orangeplastic.deb.html. Retrieved 2007-0909. 13. ^ Austell, J Michael (2005). "CO2 for Enhanced Oil Recovery Needs - Enhanced Fiscal Incentives". Exploration & Production: the Oil & Gas Review. http://www.touchoilandgas.com/enhanced-recovery-needs-enhanced-a423-1.html. Retrieved 2007-09-28. 14. ^ "The Coca-Cola Company Announces Adoption of HFC-Free Insulation in Refrigeration Units to Combat Global Warming". The Coca-Cola Company. 2006-06-05. http://www.thecoca-colacompany.com/presscenter/nr_20060605_corporate_hfcfree.html. Retrieved 2007-10-11. 15. ^ "Modine reinforces its CO2 research efforts". R744.com. 2007-06-28. http://www.r744.com/news/news_ida145.php. 16. ^ "Enhanced coal bed methane recovery". ETH Zurich. 2006-08-31. http://www.ipe.ethz.ch/laboratories/spl/research/adsorption/project03.

17. ^ Dr. Pieter Tans (3 May 2008) "Annual CO2 mole fraction increase (ppm)" for 1959-

2007 National Oceanic and Atmospheric Administration Earth System Research Laboratory, Global Monitoring Division (additional details.) 18. ^ "Climate and CO2 in the Atmosphere". http://earthguide.ucsd.edu/virtualmuseum/climatechange2/07_1.shtml. Retrieved 200710-10. 19. ^ Berner, Robert A.; Kothavala, Zavareth (2001). "GEOCARB III: A Revised Model of Atmospheric CO2 over Phanerozoic Time" (PDF). American Journal of Science 301: 182–204. doi:10.2475/ajs.301.2.182. http://www.geocraft.com/WVFossils/Reference_Docs/Geocarb_III-Berner.pdf. Retrieved 2008-02-15. 20. ^ "After two large annual gains, rate of atmospheric CO2 increase returns to average". NOAA News Online, Story 2412. 2005-03-31. http://www.noaanews.noaa.gov/stories2005/s2412.htm. 21. ^ Sigurdsson, Haraldur; Houghton, B. F. (2000). Encyclopedia of volcanoes. San Diego: Academic Press. ISBN 012643140X. 22. ^ van Gardingen, P.R.; Grace, J.; Jeffree, C.E.; Byari, S.H.; Miglietta, F.; Raschi, A.; Bettarini, I. (1997). "Long-term effects of enhanced CO2 concentrations on leaf gas exchange: research opportunities using CO2 springs". in Raschi, A.; Miglietta, F.; Tognetti, R.; van Gardingen, P.R. (Eds.). Plant responses to elevated CO2: Evidence from natural springs. Cambridge: Cambridge University Press. pp. 69–86. ISBN 0521582032. 23. ^ Martini, M. (1997). "CO2 emissions in volcanic areas: case histories and hazaards". in Raschi, A.; Miglietta, F.; Tognetti, R.; van Gardingen, P.R. (Eds.). Plant responses to elevated CO2: Evidence from natural springs. Cambridge: Cambridge University Press. pp. 69–86. ISBN 0521582032. 24. ^ "Volcanic Gases and Their Effects". http://volcanoes.usgs.gov/Hazards/What/VolGas/volgas.html. Retrieved 2007-09-07. 25. ^ Doney, Scott C.; Naomi M. Levine (2006-11-29). "How Long Can the Ocean Slow Global Warming?". Oceanus. http://www.whoi.edu/oceanus/viewArticle.do?id=17726. Retrieved 2007-11-21. 26. ^ Garrison, Tom (2004). Oceanography: An Invitation to Marine Science. Thomson Brooks. pp. 125. ISBN 0534408877. 27. ^ Blom, T.J.; W.A. Straver; F.J. Ingratta; Shalin Khosla; Wayne Brown (2002-12). "Carbon Dioxide In Greenhouses". http://www.omafra.gov.on.ca/english/crops/facts/00077.htm. Retrieved 2007-06-12. 28. ^ Global Warming? What a load of poppycock! by Professor David Bellamy Daily Mail, July 9, 2004 29. ^ F. Woodward and C. Kelly (1995). "The influence of CO2 concentration on stomatal density". New Phytologist 131: 311–327. doi:10.1111/j.1469-8137.1995.tb03067.x. 30. ^ Bert G. Drake et al. (1997). "More efficient plants: A Consequence of Rising Atmospheric CO2?". Annual Review of Plant Physiology and Plant Molecular Biology 48: 609. doi:10.1146/annurev.arplant.48.1.609. 31. ^ Loladze, I (2002). "Rising atmospheric CO2 and human nutrition: toward globally imbalanced plant stoichiometry?". Trends in Ecology & Evolution 17: 457. doi:10.1016/S0169-5347(02)02587-9.

32. ^ Carlos E. Coviella and John T. Trumble (1999). "Effects of Elevated Atmospheric

Carbon Dioxide on Insect-Plant Interactions". Conservation Biology 13 (4): 700. http://www.jstor.org/stable/2641685. 33. ^ "Global Environment Division Greenhouse Gas Assessment Handbook - A Practical Guidance Document for the Assessment of Project-level Greenhouse Gas Emissions". World Bank. http://wwwwds.worldbank.org/external/default/WDSContentServer/WDSP/IB/2002/09/07/00009494 6_02081604154234/Rendered/INDEX/multi0page.txt. Retrieved 2007-11-10. 34. ^ . doi:10.1038/nature07276. 35. ^ Falkowski, P.; Scholes, R.J.; Boyle, E.; Canadell, J.; Canfield, D.; Elser, J.; Gruber, N.; Hibbard, K.; Hogberg, P.; Linder, S.; Mackenzie, F.T.; Moore, B 3rd.; Pedersen, T.; Rosenthal, Y.; Seitzinger, S.; Smetacek V.; Steffen W. (2000). "The global carbon cycle: a test of our knowledge of earth as a system". Science 290 (5490): 291–296. doi:10.1126/science.290.5490.291. PMID 11030643. 36. ^ a b c d e Davidson, Clive. 7 February 2003. "Marine Notice: Carbon Dioxide: Health Hazard". Australian Maritime Safety Authority. 37. ^ "Graphical map of CO2". http://www.esrl.noaa.gov/gmd/ccgg/carbontracker/. 38. ^ Occupational Safety and Health Administration. Chemical Sampling Information: Carbon Dioxide. Retrieved 5 June 2008 from: http://www.osha.gov/dts/chemicalsampling/data/CH_225400.html 39. ^ Lambertsen, C. J. (1971). "Carbon Dioxide Tolerance and Toxicity". Environmental Biomedical Stress Data Center, Institute for Environmental Medicine, University of Pennsylvania Medical Center (Philadelphia, PA) IFEM Report No. 2-71. http://archive.rubicon-foundation.org/3861. Retrieved 2008-05-02. 40. ^ Glatte Jr H. A., Motsay G. J., Welch B. E. (1967). "Carbon Dioxide Tolerance Studies". Brooks AFB, TX School of Aerospace Medicine Technical Report SAM-TR-6777. http Potassium chromate Home > Library > Miscellaneous > Wikipedia Not to be confused with Potassium dichromate.

Potassium chromate

IUPAC name Other names CAS number

Chromic acid, (H2CrO4), dipotassium salt Identifiers 7789-00-6

PubChem EC number RTECS number Molecular formula Molar mass Appearance Odor Density Melting point Boiling point Solubility in water Solubility MSDS EU Index EU classification R-phrases S-phrases

NFPA 704

24597 232-140-5 GB2940000 Properties CrK2O4 194.19 g mol−1 Yellow odorless powder odorless 2.7320 g/cm3 968 °C, 1241 K, 1774 °F 1000 °C, 1273 K, 1832 °F 63 g/100 mL (20 °C) insoluble in alcohol Hazards Chemical Safety Data 024-006-00-8 Carc. Cat. 2 Muta. Cat. 2 Toxic (T) Irritant (Xi) Dangerous for the environment (N) R49, R46, R36/37/38, R43, R50/53 S53, S45, S60, S61

0 3 1 OX

Related compounds Potassium dichromate Other anions Potassium molybdate Potassium tungstate Sodium chromate Other cations Calcium chromate Barium chromate (what is this?) (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

Potassium chromate (K2CrO4) is a yellow chemical indicator used for identifying concentrations of chloride ions in a salt solution with silver nitrate (AgNO3). It is a class two carcinogen and can cause cancer on inhalation.[1]

Contents [hide] • • •

•

1 General information o 1.1 Physical properties 2 Reactions 3 Occurrence o 3.1 Dangers/Hazards 4 References

General information Physical properties Potassium Chromate is a lemon yellow compound that is in the form of a crystalline solid, and it is very stable.[citation needed]

Reactions When reacted with Lead(II) Nitrate, it creates an orange-yellow precipitate, Lead(II) Chromate, Silver Nitrate, and Potassium Nitrate. All ions hydrolyze in solution.

Occurrence Tarapacaite is the natural, mineral form of potassium chromate. It occurs very rarely and until now is known from only few localities on Atacama desert.[citation needed]

Dangers/Hazards Potassium Chromate is very toxic and may be fatal if swallowed. It may also act as a carcinogen, and can create reproductive defects if inhaled or swallowed. It also is a strong oxidizing agent. It may react rapidly, or violently. It is also possible that it may react explosively with other reducing agents and flammable objects.

References 1. ^ Potassium chromate information URL last accessed 15 March 2007

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Potassium compounds

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Is potassium chromate soluble in water? Read answer... Formula for potassium chromate? Read answer... What is the formula for potassium chromate? Read answer... Help us answer these What is potassium chromate made of? What is the literal value of potassium chromate? What does potassium chromate make? Single displacement reaction Sponsored Links European men Do you want to meet with european men from germany, austria, etc www.AsianKisses.de Dating Singles Want to Date Quality Singles? Just Select & Meet – Easy & Free AdvantisMatchmaker.com Home > Library > Miscellaneous > Wikipedia A single-displacement reaction, also called single-replacement reaction, is a type of oxidation-reduction chemical reaction when an element or ion moves out of one compound and into another. (One element is replaced by another in a compound.) This is usually written as

A + BX → AX + B This will occur if A is more reactive than B. You can refer to the reactivity series to be sure of this. Based on Standard Potentials, K>Ba>Ca>Na>Mg>Al>Mn>Zn>Fe>Ni>Sn>Pb>Cu>Ag. A and B must be either: • •

different metals (hydrogen's behavior as a cation renders it as a metal here), in which case X represents an anion; or halogens, in which case X represents a cation.

In either case, when AX and BX are aqueous compounds (which is usually the case), X is a spectator ion. Due to the free state nature of A and B, all single displacement reactions are also oxidationreduction reactions. When A and B are metals, A is always oxidized and B is always reduced. Since halogens prefer to gain electrons, A is reduced (from a 0 to −1) and B is oxidized (from −1 to 0) when A and B represent those elements. A and B may not have the same charge when ions are formed therefore some balancing of the equation may be necessary. For example the reaction between silver nitrate, AgNO3, and zinc, Zn, forms silver, Ag, and zinc nitrate, Zn(NO3)2. 2AgNO3(aq) + Zn(s) → 2Ag(s) + Zn(NO3)2(aq) All simple metal with acid reactions are single displacement reactions. For example the reaction between magnesium, Mg, and hydrochloric acid, HCl, forms magnesium chloride, MgCl2, and hydrogen, H2. Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)

Cation replacement One cation replaces another. A cation is a positively charged ion or a metal. When it is written in generic symbols, it is written out like this: AX + Y → YXh Element Y has replaced A (in the compound AX) to become a new compound YX and the free element A. This is an oxidation-reduction reaction wherein element A is reduced from a cation into the elemental form and element Y is oxidized from the elemental form into a cation. Some examples are: 1. Cu + 2AgNO3 → 2Ag + Cu(NO3)2 2. Fe + Cu(NO3)2 → Fe(NO3)2 + Cu 3. Ca + 2H2O → Ca(OH)2 + H2

4. Zn + 2HCl → ZnCl2 + H2

Anion replacement One anion replaces another. An anion is a negatively charged ion or a nonmetal. Written using generic symbols, it is: A + XY → XA + Y Element A has replaced Y (in the compound XY) to form a new compound XA and the free element Y. This is an oxidation-reduction reaction wherein element A is reduced from the elemental form into an anion and element Y is oxidized from an anion into the elemental form. Some of the only examples that involve halogens are here, so here are the two examples: 1. Cl2 + 2NaBr → 2NaCl + Br2 2. Br2 + 2KI → 2KBr + I2

See also •

Double displacement reaction

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Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Single displacement reaction". Read more activation energy Home > Library > Miscellaneous > Britannica Concise Encyclopedia Minimum amount of energy (heat, electromagnetic radiation, or electrical energy) required to activate atoms or molecules to a condition in which it is equally likely that they will undergo chemical reaction or transport as it is that they will return to their original state. Chemists posit a transition state between the initial conditions and the product conditions and theorize that the activation energy is the amount of energy required to boost the initial materials "uphill" to the transition state; the reaction then proceeds "downhill" to form the product materials. Catalysts (including enzymes) lower the activation energy by altering the transition state. Activation energies are determined by experiments that measure them as the constant of proportionality in the equation describing the dependence of reaction rate on temperature, proposed by Svante Arrhenius. See also entropy, heat of reaction. For more information on activation energy, visit Britannica.com. Columbia Encyclopedia: activation energy Top Home > Library > Miscellaneous > Columbia Encyclopedia activation energy, in chemistry, minimum energy needed to cause a chemical reaction. A chemical reaction between two substances occurs only when an atom, ion, or molecule of one collides with an atom, ion, or molecule of the other. Only a fraction of the total collisions result in a reaction, because usually only a small percentage of the substances interacting have the minimum amount of kinetic energy a molecule must possess for it to react. When the reactants collide, they may form an intermediate product whose chemical energy is higher than the combined chemical energy of the reactants. In order for this transition state in the reaction to be achieved, some energy must enter into the reaction other than the chemical energy of the reactants. This energy is the activation energy. Once the intermediate product, or activated complex, is formed, the final products are formed from it. The path from reactants through the activated complex to the final products is known as the reaction mechanism. (Reaction mechanisms for complex reactions may involve several steps analogous to that described here.) Because the heat energy of a substance is not uniformly distributed among its atoms, ions, or molecules, some may carry enough heat energy to react while others do not. If the activation energy is low, a greater proportion of the collisions between reactants will result in reactions. If the temperature of the system is increased, the average heat energy is increased, a greater proportion of collisions between reactants result in reaction, and the reaction proceeds more rapidly. A catalyst increases the reaction rate by providing a reaction mechanism with a lower activation energy, so that a greater proportion of collisions result in reaction. The activation energy and rate of a reaction are related by the equation k=Aexp(−Ea/RT), where k is the rate constant, A is a temperature-independent constant (often called the frequency factor), exp is the function ex, Ea is the activation energy, R is the universal gas constant, and T is the temperature.

This relationship was derived by Arrhenius in 1899. Because the relationship of reaction rate to activation energy and temperature is exponential, a small change in temperature or activation energy causes a large change in the rate of the reaction. Activation energies are usually determined experimentally by measuring the reaction rate k at different temperatures T, plotting the logarithm of k against 1/T on a graph, and determining the slope of the straight line that best fits the points. Wikipedia: Activation energy Top Home > Library > Miscellaneous > Wikipedia

The sparks generated by striking steel against a flint provide the activation energy to initiate combustion in this Bunsen burner. The blue flame will sustain itself after the sparks are extinguished because the continued combustion of the flame is now energetically favorable. In chemistry, activation energy is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined as the energy that must be overcome in order for a chemical reaction to occur. Arrhenius' research was a follow up of the theories of reaction rate by Serbian physicist Nebojsa Lekovic. Activation energy may also be defined as the minimum energy required to start a chemical reaction. The activation energy of a reaction is usually denoted by Ea, and given in units of kilojoules per mole. Activation energy can be thought of as the height of the potential barrier (sometimes called the energy barrier) separating two minima of potential energy (of the reactants and products of a reaction). For a chemical reaction to have a noticeable rate, there should be a noticeable number of molecules with energy equal to or greater than the activation energy.

Contents [hide]

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1 Negative activation energy 2 Temperature independence and the relation to the Arrhenius equation 3 Catalysis 4 See also

•

5 External links

Negative activation energy In some cases rates of reaction decrease with increasing temperature. When following an approximately exponential relationship so the rate constant can still be fit to an Arrhenius expression, this results in a negative value of Ea. Reactions exhibiting these negative activation energies are typically barrierless reactions, in which the reaction proceeding relies on the capture of the molecules in a potential well. Increasing the temperature leads to a reduced probability of the colliding molecules capturing one another (with more glancing collisions not leading to reaction as the higher momentum carries the colliding particles out of the potential well), expressed as a reaction cross section that decreases with increasing temperature. Such a situation no longer leads itself to direct interpretations as the height of a potential barrier.

Temperature independence and the relation to the Arrhenius equation The Arrhenius equation gives the quantitative basis of the relationship between the activation energy and the rate at which a reaction proceeds. From the Arrhenius equation, the activation energy can be expressed as

where A is the frequency factor for the reaction, R is the universal gas constant, and T is the temperature (in kelvin). While this equation suggests that the activation energy is dependent on temperature, in regimes in which the Arrhenius equation is valid this is cancelled by the temperature dependence of k. Thus Ea can be evaluated from the rate constant at any temperature (within the validity of the Arrhenius equation).

Catalysis Main article: Catalysis

The relationship between activation energy (Ea) and enthalpy of formation (ΔH) with and without a catalyst. The highest energy position (peak position) represents the transition state. With the catalyst, the energy required to enter transition state decreases, thereby decreasing the energy required to initiate the reaction. A substance that modifies the transition state to lower the activation energy is termed a catalyst; a biological catalyst is termed an enzyme. It is important to note that a catalyst increases the rate of reaction without being consumed by it. In addition, while the catalyst lowers the activation energy, it does not change the energies of the original reactants nor products. Rather, the reactant energy and the product energy remain the same and only the activation energy is altered (lowered)..

See also • • •

Arrhenius equation Chemical kinetics Quantum tunnelling

External links • • •

"Activation energy" (from the IUPAC "Gold Book") Chapter 14: Activation energy The Activation Energy of Chemical Reactions

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What does an enzyme do to activation energy? Read answer... What activities use the most energy? Read answer... Does active transport create energy? Read answer... Help us answer these How does energy and activation energy differ? CH3NC - CH3CN The energy of activation is? Enzymes lower activation energy by? Post a question - any question - to the WikiAnswers community:

Copyrights: Sci-Tech Dictionary. McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved. Read more Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved. Read more Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/. Read more Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Activation energy". Read more

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unimolecular reaction What is an enzyme? (anatomy) Arrhenius equation overpotential catalyst (in chemistry) potential-energy surface Henry Eyring (Mexican–American physical and theoretical chemist) catalyst Organic reaction mechanism (organic chemistry) Temperature adaptation (comparative physiology and general physiology)

» More» More Glossary of Terms Used in Medicinal Chemistry (IUPAC Recommendations 1998)

A to H Contents

Active transport, Address-message concept, ADME, Affinity, Agonist, Allosteric binding sites, Allosteric enzyme, Allosteric regulation, Analog, Antagonist, Antimetabolite, Antisense

molecule, Autacoid, Autoreceptor, Bioassay, Bioisostere, Bioprecursor prodrug, Biotransformation, CADD See Computer-assisted drug design., Carrier-linked prodrug (Carrier prodrug), Cascade prodrug, Catabolism, Catabolite , Clone, Codon, Coenzyme, Combinatorial library, Combinatorial synthesis, CoMFA See Comparative Molecular Field Analysis, Comparative Molecular Field Analysis (CoMFA), Computational chemistry, Computer-assisted drug design (CADD), Congener, Cooperativity, 3D-QSAR See Three-dimensional Quantitative Structure-Activity Relationship, De novo design, Disposition See Drug disposition, Distomer, Docking studies, Double-blind study, Double prodrug (or pro-prodrug), Drug, Drug disposition, Drug latentiation, Drug targeting, Dual action drug, Efficacy, Elimination, Enzyme, Enzyme induction, Enzyme repression, Eudismic ratio, Eutomer, Genome, Hansch analysis, Hapten, Hard drug, Heteroreceptor, Homologue, Hormone, Hydrophilicity, Hydrophobicity. Active transport*

Active transport is the carriage of a solute across a biological membrane from low to high concentration that requires the expenditure of (metabolic) energy. Address-message concept Address-message concept refers to compounds in which part of the molecule is required for binding (address) and part for the biological action (message). ADME Abbreviation for Absorption, Distribution, Metabolism, Excretion. (See also Pharmacokinetics; Drug disposition). Affinity Affinity is the tendency of a molecule to associate with another. The affinity of a drug is its ability to bind to its biological target (receptor, enzyme, transport system, etc.) For pharmacological receptors it can be thought of as the frequency with which the drug, when brought into the proximity of a receptor by diffusion, will reside at a position of minimum free energy within the force field of that receptor. For an agonist (or for an antagonist) the numerical representation of affinity is the reciprocal of the equilibrium dissociation constant of the ligand-receptor complex denoted K A, calculated as the rate constant for offset (k -1) divided by the rate constant for onset (k 1). Agonist*** An agonist is an endogenous substance or a drug that can interact with a receptor and initiate a physiological or a pharmacological response characteristic of that receptor (contraction, relaxation, secretion, enzyme activation, etc.).

Allosteric binding sites Allosteric binding sites are contained in many enzymes and receptors. As a consequence of the binding to Allosteric binding sites, the interaction with the normal ligand may be either enhanced or reduced. Allosteric enzyme* An allosteric enzyme is an enzyme that contains a region to which small, regulatory molecules ("effectors") may bind in addition to and separate from the substrate binding site and thereby affect the catalytic activity. On binding the effector, the catalytic activity of the enzyme towards the substrate may be enhanced, in which case the effector is an activator, or reduced, in which case it is a de-activator or inhibitor. Allosteric regulation Allosteric regulation is the regulation of the activity of allosteric enzymes. (See also Allosteric binding sites; Allosteric enzymes). Analog An analog is a drug whose structure is related to that of another drug but whose chemical and biological properties may be quite different. (See also Congener). Antagonist*** An antagonist is a drug or a compound that opposes the physiological effects of another. At the receptor level, it is a chemical entity that opposes the receptor-associated responses normally induced by another bioactive agent. Antimetabolite*** An antimetabolite is a structural analog of an intermediate (substrate or coenzyme) in a physiologically occurring metabolic pathway that acts by replacing the natural substrate thus blocking or diverting the biosynthesis of physiologically important substances. Antisense molecule An antisense molecule is an oligonucleotide or analog thereof that is complementary to a segment of RNA (ribonucleic acid) or DNA (deoxyribonucleic acid) and that binds to it and inhibits its normal function. Autacoid

An autacoid is a biological substance secreted by various cells whose physiological activity is restricted to the vicinity of its release; it is often referred to as local hormone. Autoreceptor An autoreceptor, present at a nerve ending, is a receptor that regulates, via positive or negative feedback processes, the synthesis and/or release of its own physiological ligand. (See also Heteroreceptor). Bioassay*** A bioassay is a procedure for determining the concentration, purity, and/or biological activity of a substance (e.g., vitamin, hormone, plant growth factor, antibiotic, enzyme) by measuring its effect on an organism, tissue, cell, enzyme or receptor preparation compared to a standard preparation. Bioisostere A bioisostere is a compound resulting from the exchange of an atom or of a group of atoms with another, broadly similar, atom or group of atoms. The objective of a bioisosteric replacement is to create a new compound with similar biological properties to the parent compound. The bioisosteric replacement may be physicochemically or topologically based. (See also Isostere) Bioprecursor prodrug A bioprecursor prodrug is a prodrug that does not imply the linkage to a carrier group, but results from a molecular modification of the active principle itself. This modification generates a new compound, able to be transformed metabolically or chemically, the resulting compound being the active principle. Biotransformation Biotransformation is the chemical conversion of substances by living organisms or enzyme preparations. CADD See Computer-assisted drug design. Carrier-linked prodrug (Carrier prodrug) A carrier-linked prodrug is a prodrug that contains a temporary linkage of a given active substance with a transient carrier group that produces improved physicochemical or pharmacokinetic properties and that can be easily removed in vivo, usually by a hydrolytic cleavage.

Cascade prodrug A cascade prodrug is a prodrug for which the cleavage of the carrier group becomes effective only after unmasking an activating group. Catabolism*** Catabolism consists of reactions involving endogenous organic substrates to provide chemically available energy (e.g., ATP) and/or to generate metabolic intermediates used in subsequent anabolic reactions. Catabolite A catabolite is a naturally occurring metabolite. Clone* A clone is a population of genetically identical cells produced from a common ancestor. Sometimes, "clone" is also used for a number of recombinant DNA (deoxyribonucleic acid) molecules all carrying the same inserted sequence. Codon* A codon is the sequence of three consecutive nucleotides that occurs in mRNA which directs the incorporation of a specific amino acid into a protein or represents the starting or termination signals of protein synthesis. Coenzyme A coenzyme is a dissociable, low-molecular weight, non-proteinaceous organic compound (often nucleotide) participating in enzymatic reactions as acceptor or donor of chemical groups or electrons. Combinatorial synthesis Combinatorial synthesis is a process to prepare large sets of organic compounds by combining sets of building blocks. Combinatorial library A combinatorial library is a set of compounds prepared by combinatorial synthesis. CoMFA See Comparative Molecular Field Analysis.

Comparative Molecular Field Analysis (CoMFA)** Comparative molecular field analysis (CoMFA) is a 3D-QSAR method that uses statistical correlation techniques for the analysis of the quantitative relationship between the biological activity of a set of compounds with a specified alignment, and their three-dimensional electronic and steric properties. Other properties such as hydrophobicity and hydrogen bonding can also be incorporated into the analysis. (See also Three-dimensional Quantitative Structure-Activity Relationship [3D-QSAR]). Computational chemistry** Computational chemistry is a discipline using mathematical methods for the calculation of molecular properties or for the simulation of molecular behaviour. Computer-assisted drug design (CADD)** Computer-assisted drug design involves all computer-assisted techniques used to discover, design and optimize biologically active compounds with a putative use as drugs. Congener*** A congener is a substance literally con- (with) generated or synthesized by essentially the same synthetic chemical reactions and the same procedures. Analogs are substances that are analogous in some respect to the prototype agent in chemical structure. Clearly congeners may be analogs or vice versa but not necessarily. The term congener, while most often a synonym for homologue, has become somewhat more diffuse in meaning so that the terms congener and analog are frequently used interchangeably in the literature. Cooperativity Cooperativity is the interaction process by which binding of a ligand to one site on a macromolecule (enzyme, receptor, etc.) influences binding at a second site, e.g. between the substrate binding sites of an allosteric enzyme. Cooperative enzymes typically display a sigmoid (S-shaped) plot of the reaction rate against substrate concentration. (See also Allosteric binding sites). 3D-QSAR See Three-dimensional Quantitative Structure-Activity Relationship. De novo design** De novo design is the design of bioactive compounds by incremental construction of a ligand model within a model of the receptor or enzyme active site, the structure of which is known from X-ray or nuclear magnetic resonance (NMR) data.

Disposition See Drug disposition. Distomer A distomer is the enantiomer of a chiral compound that is the less potent for a particular action. This definition does not excude the possibility of other effect or side effect of the distomer (See also Eutomer). Docking studies Docking studies are molecular modeling studies aiming at finding a proper fit between a ligand and its binding site. Double-blind study A double-blind study is a clinical study of potential and marketed drugs, where neither the investigators nor the subjects know which subjects will be treated with the active principle and which ones will receive a placebo. Double prodrug (or pro-prodrug) A double prodrug is a biologically inactive molecule which is transformed in vivo in two steps (enzymatically and/or chemically) to the active species. Drug*** A drug is any substance presented for treating, curing or preventing disease in human beings or in animals. A drug may also be used for making a medical diagnosis or for restoring, correcting, or modifying physiological functions (e.g., the contraceptive pill). Drug disposition Drug disposition refers to all processes involved in the absorption, distribution metabolism and excretion of drugs in a living organism. Drug latentiation Drug latentiation is the chemical modification of a biologically active compound to form a new compound, which in vivo will liberate the parent compound. Drug latentiation is synonymous with prodrug design. Drug targeting

Drug targeting is a strategy aiming at the delivery of a compound to a particular tissue of the body. Dual action drug A dual action drug is a compound which combines two desired different pharmacological actions at a similarly efficacious dose. Efficacy Efficacy describes the relative intensity with which agonists vary in the response they produce even when they occupy the same number of receptors and with the same affinity. Efficacy is not synonymous to Intrinsic activity. Efficacy is the property that enables drugs to produce responses. It is convenient to differentiate the properties of drugs into two groups, those which cause them to associate with the receptors (affinity) and those that produce stimulus (Efficacy). This term is often used to characterize the level of maximal responses induced by agonists. In fact, not all agonists of a receptor are capable of inducing identical levels of maximal responses. Maximal response depends on the efficiency of receptor coupling, i.e., from the cascade of events, which, from the binding of the drug to the receptor, leads to the observed biological effect. Elimination Elimination is the process achieving the reduction of of the concentration of a xenobiotic including its metabolism. Enzyme* An enzyme is a macromolecule, usually a protein, that functions as a (bio) catalyst by increasing the reaction rate. In general, an enzyme catalyzes only one reaction type (reaction selectivity) and operates on only one type of substrate (substrate selectivity). Substrate molecules are transformed at the same site (regioselectivity) and only one or preferentially one of chiral a substrate or of a racemate is transformed (enantioselectivity[special form of stereoselectivity]). Enzyme induction* Enzyme induction is the process whereby an (inducible) enzyme is synthesized in response to a specific inducer molecule. The inducer molecule (often a substrate that needs the catalytic activity of the inducible enzyme for its metabolism) combines with a repressor and thereby prevents the blocking of an operator by the repressor leading to the translation of the gene for the enzyme. Enzyme repression*

Enzyme repression is the mode by which the synthesis of an enzyme is prevented by repressor molecules. In many cases, the end product of a synthesis chain (e.g., an amino acid) acts as a feed-back corepressor by combining with an intracellular aporepressor protein, so that this complex is able to block the function of an operator. As a result, the whole operation is prevented from being transcribed into mRNA, and the expression of all enzymes necessary for the synthesis of the end product enzyme is abolished. Eudismic ratio Eudismic ratio is the potency of the eutomer relative to that of the distomer. Eutomer The Eutomer is the enantiomer of a chiral compound that is the more potent for a particular action (See also Distomer). Genome* A genome is the complete set of chromosomal and extrachromosomal genes of an organism, a cell, an organelle or a virus; the complete DNA (deoxyribonucleic acid) component of an organism. Hansch analysis** Hansch analysis is the investigation of the quantitative relationship between the biological activity of a series of compounds and their physicochemical substituent or global parameters representing hydrophobic, electronic, steric and other effects using multiple regression correlation methodology. Hapten*** A hapten is a low molecular weight molecule that contains an antigenic determinant but which is not itself antigenic unless combined with an antigenic carrier. Hard drug A hard drug is a nonmetabolizable compound, characterized either by high lipid solubility and accumulation in adipose tissues and organelles, or by high water solubility. In the lay press the term "Hard Drug" refers to a powerful drug of abuse such as cocaine or heroin. Heteroreceptor

A heteroreceptor is a receptor regulating the synthesis and/or the release of mediators other than its own ligand (See also Autoreceptor). Homologue The term homologue is used to describe a compound belonging to a series of compounds differing from each other by a repeating unit, such as a methylene group, a peptide residue, etc. Hormone*** A hormone is a substance produced by endocrine glands, released in very low concentration into the bloodstream, and which exerts regulatory effects on specific organs or tissues distant from the site of secretion. Hydrophilicity** Hydrophilicity is the tendency of a molecule to be solvated by water. Hydrophobicity** Hydrophobicity is the association of non-polar groups or molecules in an aqueous environment which arises from the tendency of water to exclude non polar molecules. (See also Lipophilicity). Continue with terms starting with I to X.

Return to home page for Glossary of Terms Used in Medicinal Chemistry. Chemical decomposition Sponsored Links Experiment Library Design Design experiment libraries for a variety of chemistry applications. www.symyx.com Synthesis Chemistry Visit our catalog for the full list of pharmaceutical API + exipients! www.merck-chemicals.com Home > Library > Miscellaneous > Wikipedia

Chemical decomposition or analysis is the separation of a chemical compound into elements or smaller compounds. It is sometimes defined as the opposite of a chemical synthesis. Chemical

decomposition is often an undesired chemical reaction. The stability that a chemical compound ordinarily has is eventually limited when exposed to extreme environmental conditions like heat, radiation, humidity or the acidity of a solvent. The details of decomposition processes are generally not well defined, as a molecule may break up into a host of smaller fragments. Chemical decomposition is exploited in several analytical techniques, notably mass spectrometry, traditional gravimetric analysis, and thermogravimetric analysis. A broader definition of the term decomposition also includes the breakdown of one phase into two or more phases.[1] There are broadly 3 types of decomposition reactions: thermal,electrolytic and catalytic.[citation needed]

Contents [hide]

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1 Reaction formulae o 1.1 Additional examples 2 See also 3 References

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4 External links

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Reaction formulae The generalized reaction formula for chemical decomposition is: AB → A + B with a specific example being the electrolysis of water to gaseous hydrogen and oxygen: 2H2O → 2H2 + O2

Additional examples An example of spontaneous decomposition is that of hydrogen peroxide, which will slowly decompose into water and oxygen: 2H2O2 → 2H2O + O2 Carbonates will decompose when heated, a notable exception being that of carbonic acid, H2CO3. Carbonic acid, the "fizz" in sodas, pop cans and other carbonated beverages, will decompose over time (spontaneously) into carbon dioxide and water

H2CO3 → H2O + CO2 Other carbonates will decompose when heated producing the corresponding metal oxide and carbon dioxide. In the following equation M represents a metal: MCO3 → MO + CO2 A specific example of this involving calcium carbonate: CaCO3 → CaO + CO2 Metal chlorates also decompose when heated. A metal chloride and oxygen gas are the products. MClO3 → MCl + O2 A common decomposition of a chlorate to evolve oxygen utilizes potassium chlorate as follows: 2KClO3 → 2KCl + 3O2

See also Look up Chemical decomposition in Wiktionary, the free dictionary. • •

Analytical chemistry Thermal decomposition

References 1. ^ International Union of Pure and Applied Chemistry. "decomposition". Compendium of

Chemical Terminology Internet edition.

External links •

Biodegradation database

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The 2008 Nobel prize in Economics, Peace, Literature, Chemistry, Physics, and Physiology or Medicine and the Ig-Nobel Prizes have been announced. While you're here, why not also read about past winners. N.B. The time of the announcement is given in Stockholm time (Central European Time); subtract 6 hours to get the US Eastern Daylight Time).

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Date: Monday, October 13, 2008 (13:00 CEST at the earliest) Prize: ECONOMICS Awarding institution: The Royal Swedish Academy of Sciences And the prize goes to...

Paul Krugman "for his analysis of trade patterns and location of economic activity". Date: Friday, October 9, 2008 (11:00 a.m. CEST)

Prize: PEACE Awarding institution: The Norwegian Nobel Institute And the prizes go to...

Martti Ahtisaari "for his important efforts, on several continents and over more than three decades, to resolve international conflicts" Date: Thursday, October 9, 2008 (13:00 p.m. CEST. at the earliest) Prize: LITERATURE Awarding institution: The Swedish Academy And the prize goes to...

Jean-Marie Gustave Le Clézio "author of new departures, poetic adventure and sensual ecstasy, explorer of a humanity beyond and below the reigning civilization" Date: Wednesday, October 8, 2008 (11:45 a.m. CEST at the earliest) Prize: CHEMISTRY Awarding institution: The Royal Swedish Academy of Sciences And the prize goes to...

Osamu Shimomura, Martin Chalfie, and Roger Y. Tsien "for the discovery and development of the green fluorescent protein, GFP". Date: Tuesday, October 7, 2008 (11:45 a.m. CEST at the earliest) Prize: PHYSICS Awarding institution: The Royal Swedish Academy of Sciences And the prizes go to...

Yoichiro Nambu "for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics" and

Makoto Kobayashi and Toshihide Maskawa "for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature" Date: Monday, October 6, 2008 (11:30 a.m. CEST at the earliest) Prize: PHYSIOLOGY or MEDICINE Awarding institution: The Nobel Assembly at the Karolinska Institute And the prizes go to...

Harald zur Hausen "for his discovery of human papilloma viruses causing cervical cancer" and

Françoise Barré-Sinoussi and Luc Montagnier for their discovery of human immunodeficiency virus Date: Thursday, October 2, 2008 (7:30 pm EDT) Prize: IG NOBEL PRIZES Awarding institution: The Annals of Improbable Research And the winners are: NUTRITION PRIZE: Massimiliano Zampini of the University of Trento, Italy and Charles Spence of Oxford University, UK, for electronically modifying the sound of a potato chip to make the person chewing the chip believe it to be crisper and fresher than it really is. REFERENCE: "The Role of Auditory Cues in Modulating the Perceived Crispness and Staleness of Potato Chips," Massimiliano Zampini and Charles Spence, Journal of Sensory Studies, vol. 19, October 2004, pp. 347-63. PEACE PRIZE: The Swiss Federal Ethics Committee on Non-Human Biotechnology (ECNH) and the citizens of Switzerland for adopting the legal principle that plants have dignity. REFERENCE: "The Dignity of Living Beings With Regard to Plants. Moral Consideration of Plants for Their Own Sake" WHO ATTENDED THE CEREMONY: Urs Thurnherr, member of the committee. ARCHAEOLOGY PRIZE Astolfo G. Mello Araujo and Jose Carlos Marcelino of Universidade de Sao Paulo, Brazil, for measuring how the course of history, or at least the contents of an archaeological dig site, can be scrambled by the actions of a live armadillo. REFERENCE: "The Role of Armadillos in the Movement of Archaeological Materials: An Experimental Approach," Astolfo G. Mello Araujo and Jose Carlos Marcelino, Geoarchaeology, vol. 18, no. 4, April 2003, pp. 433-60. BIOLOGY PRIZE: Marie-Christine Cadiergues, Christel Joubert,, and Michel Franc of Ecole Nationale Veterinaire de Toulouse, France for discovering that the fleas that live on a dog can jump higher than the fleas that live on a cat. REFERENCE: "A Comparison of Jump Performances of the Dog Flea, Ctenocephalides canis (Curtis, 1826) and the Cat Flea, Ctenocephalides felis felis (Bouche, 1835)," M.C. Cadiergues, C. Joubert, and M. Franc, Veterinary Parasitology, vol. 92, no. 3, October 1, 2000, pp. 239-41. MEDICINE PRIZE: Dan Ariely of Duke University, USA, for demonstrating that high-priced fake medicine is more effective than low-priced fake medicine. REFERENCE: "Commercial Features of Placebo and Therapeutic Efficacy," Rebecca L. Waber; Baba Shiv; Ziv Carmon; Dan Ariely, Journal of the American Medical Association, March 5, 2008; 299: 10161017.

WHO ATTENDED THE CEREMONY: Dan Ariely COGNITIVE SCIENCE PRIZE: Toshiyuki Nakagaki of Hokkaido University, Japan, Hiroyasu Yamada of Nagoya, Japan, Ryo Kobayashi of Hiroshima University, Atsushi Tero of Presto JST, Akio Ishiguro of Tohoku University, and Agota Toth of the University of Szeged, Hungary, for discovering that slime molds can solve puzzles. REFERENCE: "Intelligence: Maze-Solving by an Amoeboid Organism," Toshiyuki Nakagaki, Hiroyasu Yamada, and Agota Toth, Nature, vol. 407, September 2000, p. 470. WHO ATTENDED THE CEREMONY: Toshiyuki Nakagaki, Ryo Kobayashi, Atsushi Tero ECONOMICS PRIZE: Geoffrey Miller, Joshua Tybur and Brent Jordan of the University of New Mexico, USA, for discovering that a professional lap dancer's ovulatory cycle affects her tip earnings. REFERENCE: "Ovulatory Cycle Effects on Tip Earnings by Lap Dancers: Economic Evidence for Human Estrus?" Geoffrey Miller, Joshua M. Tybur, Brent D. Jordan, Evolution and Human Behavior, vol. 28, 2007, pp. 375-81. WHO ATTENDED THE CEREMONY: Geoffrey Miller and Brent Jordan PHYSICS PRIZE: Dorian Raymer of the Ocean Observatories Initiative at Scripps Institution of Oceanography, USA, and Douglas Smith of the University of California, San Diego, USA, for proving mathematically that heaps of string or hair or almost anything else will inevitably tangle themselves up in knots. REFERENCE: "Spontaneous Knotting of an Agitated String," Dorian M. Raymer and Douglas E. Smith, Proceedings of the National Academy of Sciences, vol. 104, no. 42, October 16, 2007, pp. 16432-7. WHO ATTENDED THE CEREMONY: Dorian Raymer CHEMISTRY PRIZE: Sharee A. Umpierre of the University of Puerto Rico, Joseph A. Hill of The Fertility Centers of New England (USA), Deborah J. Anderson of Boston University School of Medicine and Harvard Medical School (USA), for discovering that Coca-Cola is an effective spermicide, and to Chuang-Ye Hong of Taipei Medical University (Taiwan), C.C. Shieh, P. Wu, and B.N. Chiang (all of Taiwan) for discovering that it is not. REFERENCE: "Effect of 'Coke' on Sperm Motility," Sharee A. Umpierre, Joseph A. Hill, and Deborah J. Anderson, New England Journal of Medicine, 1985, vol. 313, no. 21, p. 1351. REFERENCE: "The Spermicidal Potency of Coca-Cola and Pepsi-Cola," C.Y. Hong, C.C. Shieh, P. Wu, and B.N. Chiang, Human Toxicology, vol. 6, no. 5, September 1987, pp. 395-6. [NOTE: THE JOURNAL LATER CHANGED ITS NAME. NOW CALLED "Human & experimental toxicology"] WHO ATTENDED THE CEREMONY: Deborah Anderson, and C.Y. Hong's daughter Wan Hong LITERATURE PRIZE: David Sims of Cass Business School. London, UK, for his lovingly written study "You Bastard: A Narrative Exploration of the Experience of Indignation within Organizations." REFERENCE: "You Bastard: A Narrative Exploration of the Experience of Indignation within Organizations," David Sims, Organization Studies, vol. 26, no. 11, 2005, pp. 1625-40. WHO ATTENDED THE CEREMONY: David Sims

2002 Nobel Prize Announcements
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The 2002 Peace, Literature, Economics, Chemistry, Physiology or Medicine, and Physics Nobel Prizes and Ig-Nobel Prizes have been announced! The time of the announcement is given in Stockholm time; subtract 6 hours to get the US Eastern Standard Time). If you use a JavaScript-enabled browser, move your mouse over the prize category and the status bar will display how soon the prize in this category will be announced.

Date: Friday, October 11, 2002 (11:00 a.m.) Prize: PEACE Awarding institution: The Norwegian Nobel Institute And the winner is...

Jimmy Carter, Jr. "for his decades of untiring effort to find peaceful solutions to international conflicts, to advance democracy and human rights, and to promote economic and social development" Date: Thursday, October 10, 2002 (1:00 p.m. at the earliest) Prize: LITERATURE Awarding institution: The Swedish Academy And the winner is...

Imre Kertesz "for writing that upholds the fragile experience of the individual against the barbaric arbitrariness of history" Date: Wednesday, October 9, 2002 (15:30 p.m. at the earliest) Prize: ECONOMICS Awarding institution: The Royal Swedish Academy of Sciences And the winners are...

Daniel Kahneman "for having integrated insights from psychological research into economic science, especially concerning human judgment and decision-making under uncertainty" and

Vernon L. Smith "for having established laboratory experiments as a tool in empirical economic analysis, especially in the study of alternative market mechanisms" Date: Wednesday, October 9, 2002 (11:45 a.m. at the earliest) Prize: CHEMISTRY Awarding institution: The Royal Swedish Academy of Sciences And the winners are... "for the development of methods for identification and structure analyses of biological

macromolecules"

John B. Fenn and Koichi Tanaka "for their development of soft desorption ionisation methods for mass spectrometric analyses of biological macromolecules" and

Kurt Wüthrich "for his development of nuclear magnetic resonance spectroscopy for determining the three-dimensional structure of biological macromolecules in solution" Date: Tuesday, October 8, 2002 (11:45 a.m. at the earliest) Prize: PHYSICS Awarding institution: The Royal Swedish Academy of Sciences And the winners are...

Raymond Davis Jr, and Masatoshi Koshiba "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos" and

Riccardo Giacconi "for pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources". Date: Monday, October 7, 2002 (11:30 a.m. at the earliest) Prize: PHYSIOLOGY or MEDICINE Awarding institution: The Nobel Assembly at the Karolinska Institute And the winners are...

Sydney Brenner, H. Robert Horvitz, John E. Sulston "for their discoveries concerning genetic regulation of organ development and programmed cell death" Date: Thursday, October 3, 2002 at 7:30 pm EDT Prize: IG NOBEL PRIZES Awarding institution: The Annals of Improbable Research And the winners are: MEDICINE Chris McManus of University College London, for his excruciatingly balanced report, "Scrotal Asymmetry in Man and in Ancient Sculpture."

PUBLISHED IN: Nature, vol. 259, February 5, 1976, p. 426. PHYSICS Arnd Leike of the University of Munich, for demonstrating that beer froth obeys the mathematical Law of Exponential Decay. REFERENCE: "Demonstration of the Exponential Decay Law Using Beer Froth," Arnd Leike, European Journal of Physics, vol. 23, January 2002, pp. 21-26. INTERDISCIPLINARY RESEARCH Karl Kruszelnicki of The University of Sydney, for performing a comprehensive survey of human belly button lint -- who gets it, when, what color, and how much. BIOLOGY Norma E. Bubier, Charles G.M. Paxton, Phil Bowers, and D. Charles Deeming of the United Kingdom, for their report "Courtship Behaviour of Ostriches Towards Humans Under Farming Conditions in Britain." REFERENCE: "Courtship Behaviour of Ostriches (Struthio camelus) Towards Humans Under Farming Conditions in Britain," Norma E. Bubier, Charles G.M. Paxton, P. Bowers, D.C. Deeming, British Poultry Science, vol. 39, no. 4, September 1998, pp. 477-481. CHEMISTRY Theo Gray of Wolfram Research, in Champaign, Illinois, for gathering many elements of the periodic table, and assembling them into the form of a four-legged periodic table table. MATHEMATICS K.P. Sreekumar and the late G. Nirmalan of Kerala Agricultural University, India, for their analytical report "Estimation of the Total Surface Area in Indian Elephants." REFERENCE: "Estimation of the Total Surface Area in Indian Elephants (Elephas maximus indicus)," K.P. Sreekumar and G. Nirmalan, Veterinary Research Communications, vol. 14, no. 1, 1990, pp. 5-17. LITERATURE Vicki L. Silvers of the University of Nevada-Reno and David S. Kreiner of Missouri State University, for their colorful report "The Effects of Pre-Existing Inappropriate Highlighting on Reading Comprehension." PUBLISHED IN: Reading Research and Instruction, vol. 36, no. 3, 1997, pp. 217-23. ECONOMICS The executives, corporate directors, and auditors of Enron, Lernaut & Hausbie [Belgium], Adelphia, Bank of Commerce and Credit International [Pakistan], Cendant, CMS Energy, Duke Energy, Dynegy, Gazprom [Russia], Global Crossing, HIH Insurance [Australia], Informix, Kmart, Maxwell Communications [UK], McKessonHBOC, Merrill Lynch, Merck, Peregrine Systems, Qwest Communications, Reliant Resources, Rent-Way, Rite Aid, Sunbeam, Tyco, Waste Management, WorldCom, Xerox, and Arthur Andersen, for adapting the mathematical concept of imaginary numbers for use in the business world. [NOTE: all companies are US-based unless otherwise noted.] PEACE Keita Sato, President of Takara Co., Dr. Matsumi Suzuki, President of Japan Acoustic Lab, and Dr. Norio Kogure, Executive Director, Kogure Veterinary Hospital, for promoting peace and harmony between the species by inventing Bow-Lingual, a computer-based automatic dog-to-human language translation device. HYGIENE Eduardo Segura, of Lavakan de Aste, in Tarragona, Spain, for inventing a washing machine for cats and dogs. "Chemistry Overview"

Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

Chemistry Overview The Field - Preparation - Co-ops/Internships/Summer Work Career Options - Earnings - Job Hunting - Challenges Professional Organizations

The Field Chemistry is the central science. It is the science about substances, their composition, structure, properties, and interactions. Chemistry helps explain the physical world and its workings, and plays an important role in our lives. Chemists have contributed a great deal to technical advances of society and have made many important contributions to modern life. Everything is made from one or more chemical elements that occur in nature. Chemists use different kinds of chemical processes to make the elements more useful, and they create countless products that make our lives healthier, easier, and more enjoyable. Chemistry is a powerful springboard to launch you into a fascinating career. Chemistry courses combine general education with preparation for immediate employment. A person with a bachelor's level education in chemistry is prepared to assume a wide variety of positions in industry, government, and academia. The more obvious positions for which a background in chemistry is important are those in the chemical industry or in chemical education. Those with a significant knowledge of chemistry are also employed in a wide variety of related professions such as molecular biology and biotechnology, material science, forensic science, hazardous waste management, textile science, and information management. There are as many specialties as there are areas of application of chemical principles. An undergraduate chemistry degree may be combined with advanced studies in other fields and lead to work in areas such as law or higher management. Chemists are challenged, excited, and satisfied with their profession. Though chemists may change employers several times during their careers, the majority in the field stay in it their entire careers. The career information in this resource has been assembled to help students majoring in chemistry and related sciences prepare for careers in the chemical sciences by describing a wide variety of chemistry careers and illustrating options available to those who obtain degrees in the chemical sciences.

"Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

Preparation Your college education is your first step toward your future chemistry career. It is a critical first step. Because chemistry offers so many different career opportunities and can be your entree into a whole spectrum of careers, scientific and nonscientific, you should consider your options; choose as your goals the fields that interest you most, and plan your education with your goals in mind. Your degree offers vital proof of your mastery of basic principles and how well you prepared for specific career options. The variety of degrees in chemistry and related fields include: Associate in Applied Science (AAS), Bachelor of Arts (B.A.) or Bachelor of Science (B.S.) degree in chemistry; Master of Science (M.S.) degree and the Master of Arts (M.A.) degree; Doctor of Philosophy (Ph.D.) degree; and Doctor of Arts (D.A.) degree. Some receive additional training in postdoctoral positions. Since the chemical industry has become globalized, you may want to include the study of a foreign language if you are considering a career in industry. How much education is enough? The answer to this question depends on your interests, abilities, and career goals.

AAS / BA / BS The Associate in Applied Science (AAS) is offered to those wishing to complete programs in chemical technology. Many chemical technicians begin their career by earning this degree. After earning this degree, some graduates continue their studies to earn a bachelor's degree in chemistry or a related field. The Bachelor of Arts (BA) or Bachelor of Science (BS) degree in chemistry. The designation of these four year BA or BS degrees varies from one institution to another. The BS degree typically includes more chemistry, other science, and math courses. The BA degree typically includes more courses outside of science, engineering, and math.

MS / MA The Master of Science (MS) and the Master of Arts (MA) degrees in chemistry and related

fields are typically earned after two years of study after the bachelor's degree. Earning a bachelor's degree in chemistry and a master's degree in a related field (or vice versa) can be very useful to students planning an interdisciplinary career. A master's degree is essential in order to teach in a community college. It is also helpful to have a master's for a high school teaching career. A master's degree can also serve to deepen or broaden your chemistry knowledge and better prepare you for industrial careers. Some students use the master's degree to help them determine their career interests and aptitudes before making the longer commitment to a Doctor of Philosophy (PhD) chemistry program. This approach can be particularly useful to students who were not able to participate in an undergraduate research program. For them, the master's degree is their first real exposure to chemical research.

PhD / DA The Doctor of Philosophy (Ph.D.) degree in chemistry is preferred for many research positions in industry and government. Colleges and universities usually require Ph.D. degrees when they hire new faculty members. Earning a Ph.D. degree demonstrates a long-term commitment to chemistry as a career. It provides the chemist with a depth of chemical information and the knowledge of how to do productive research. "Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

Post-doc Many research universities and some colleges prefer that employment candidates also complete some postdoctoral (post-doc) research in addition to earning their Ph.D. In postdoctoral research, Ph.D. chemists work with a professor or chemical professional in industry on a research project but do so more independently than they did as graduate students. Usually, they leave the institution where they earned their Ph.D. to work in another university, industrial, or government laboratory. Industrial post-docs are becoming more common as are post-docs before beginning a research career in industry, particularly the pharmaceutical industry. Post-doctoral positions typically last two years. They offer chemists two opportunities. The first is to work in the same field as they did when earning their Ph.D. This provides a depth of knowledge and specialization that can be very useful if there are plentiful job opportunities in their field of specialization. The second is to work in a different field than

the one in which they earned their Ph.D. This will allow them broaden their knowledge and experience, thus qualifying them for a broader range of job opportunities and demonstrating their versatility to employers

Graduate School Considerations Before deciding whether to apply to graduate school, determine the kind of career you want. Consider both your interests and abilities when making this determination. One of the reasons so many chemists enjoy their careers is that they are a good match for their interests and abilities. Graduate school is intended to develop independent researchers and is usually the best option for those who want to spend a major portion of their career doing research and development work. However, be prepared to revise your plans as your interests change. For example, after working in research, some industrial chemists develop an interest in guiding research and determining what research areas are explored at their company. A major component of many master's degree and nearly all Ph.D. programs is research and writing a thesis. This is an intense experience. Working on an undergraduate research project will help you decide if you find research rewarding and thus would enjoy graduate school. So will working in an industrial research lab after graduation or as part of a co-op program. Of course, you'll also learn if your abilities will enable you to be a good researcher. In deciding whether to continue your education past the bachelor's degree, assess your abilities as objectively as possible. Consult your faculty advisor and other faculty members who know you well. Consult graduate students. If you know some chemists who have completed graduate school and know you, consult them as well. If they do not know you well, they can still advise you on what they think are the most important qualities you need to do well in graduate school. Success in your undergraduate studies is not a definite predictor of graduate school success. Graduate school is unique, far more than an extension of your undergraduate study. In short, graduate school requires more work, a stronger commitment, and concentrated effort as well

as creativity in research and analysis. The course work is more intense. You will have to be self-motivated and work independently to succeed at your research. This requires maturity and motivation. Writing your thesis is a major effort that both demonstrates your research accomplishments and indicates whether you can organize and effectively communicate complicated technical information to others. "Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

Your decision to attend graduate school is not final; it does not have to be made prior to receiving your undergraduate degree. Some students receive their undergraduate degree and work as chemists or in other fields before deciding to attend graduate school. A break of a year or more can offer you a chance to gain practical experience before choosing a specialty. Some are concerned that delaying graduate school to gain work experience or earn an income may ultimately lead to not returning to school to do graduate work as they get used to developing their careers and earning a salary. However, many employers encourage their employees to attend graduate school while continuing to work and often offer financial assistance to do so. Once you've decided you have the abilities and commitment to succeed in graduate school, you will have to decide on which schools to apply, complete application materials, gain admission, and decide how to finance your graduate education. Selecting a Graduate School - Graduate schools differ greatly in their degree programs. Carefully review graduate school catalogs and the research interests of the faculty members. Many universities now have web sites. By consulting them, you can get at least an introduction to various graduate programs. The ACS "Directory of Graduate Research" provides detailed information on chemistry departments' faculty size, the research interests of their faculty members, and recent faculty publications. Another ACS publication, Graduate Programs in Chemistry, provides information about the nature and scope of chemistry graduate school programs. Discuss your graduate school plans with your faculty advisor, other professors at your undergraduate school, alumni of graduate schools, and campus recruiters. Also discuss your interests and options with acquaintances already in graduate schools. Don't feel bound to enroll in the graduate program at your undergraduate institution.

(Some schools will not permit students to do graduate work in the same program at their undergraduate institution.) A change of schools will expose you to people with different attitudes about chemistry and research and widen your circle of academic contacts. Changing schools will enable you to experience different educational approaches and provide the stimulus of a new and different environment. Admission - After developing your final list of graduate schools, contract the department chairs of these schools and ask them for their admission requirements and application forms. Do this no later than the beginning of your senior year. You can write or contact the departments through their web sites. You should complete and submit your applications by the start of the second semester of your senior year. The time between semesters is an excellent opportunity to complete and submit your applications if you haven't done so already. Many schools have early admissions programs that can reduce the stress and concern you feel while waiting to hear if you have been admitted. Take advantage of these by submitting your application materials early. However, don't rush these out. Treat them like job applications and resumes. They should be letter perfect. Cover letters and long responses to questions should be examples of your best writing. Financial Aid - While your choice of a graduate school should not depend only on financial considerations, money concerns are important. Most chemistry graduate students obtain full or partial tuition scholarships. Teaching assistantships and research fellowships are part of the work component that pays for tuition and provides for some living expenses. In addition to university funding and research assistantship funding from your thesis advisor's research grant money, competitive fellowships are offered by the National Science Foundation, the National "Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

Institutes of Health, other government agencies, and some companies. The department chair or administrator can help you collect information on these funding opportunities. Education loans, often guaranteed by the government and repayable over long periods of time, are another financing option.

Co-ops / Internships / Summer Work Experiential opportunities such as co-ops, internships, and summer work are effective strategies that add value to your education and career development. These workintegrated learning programs can provide opportunities for you to apply classroom theory, advance your technical skills, learn about diverse work cultures, explore career options, and gain selfknowledge. Some schools offer undergraduate and graduate cooperative chemistry programs that combine industrial work experience with the academic program. Co-op programs can help students learn about what industrial work is like while they are still in school. A co-op program or summer internship can help you learn about various chemistry careers and give you an opportunity to test and analyze your capabilities. If you find a career or specialty that really excites you, you can tailor the remainder of your curriculum to prepare you for this career. You can also gain useful contacts in industry who can serve as references and otherwise help you in your job hunting efforts. The ACS Office of College Chemistry publishes a directory of schools offering co-op programs. The periodically updated searchable version may be found at www.acs.org/edugen2/educareer/epic/expichem.htm.

Career Options The employment outlook for chemists varies with the state of the economy, the prosperity of particular industries, the needs of specific employers, and the amount of government spending on science programs. Specifics of your own situation will also affect how many employment opportunities you find in the job market. These specifics include: 1. Your education level 2. Your technical specialty 3. Previous job and practical experience. (In addition to previous job and research experience, this can include professional society activities, college extracurricular activities, and volunteer work.) 4. Skills and traits such as communications skills, business sense, leadership skills, initiative, teamwork, and versatility 5. Geographic restrictions on relocation Chemistry career options include those in industry, government, and academia. Career opportunities also available in areas outside of the traditional laboratory or academic setting (nontraditional careers for chemists). The Profiles section highlights various careers of chemical professionals in industry,

government, and academia, and includes both traditional and nontraditional careers in the chemical sciences. The profiles give a summary of the jobs performed by the chemical professionals profiled. "Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

General Discussion Common career options for chemists with bachelor's degrees include chemical sales, working as a plant chemist, working in a quality control laboratory, working as a laboratory technician. Careful choice of a minor or a sequence of elective courses can be critical. The right choices can aid a B.A. or B.S. chemist in becoming a high school science teacher, working in chemical sales, or beginning a career in chemical marketing. Helpful electives include various engineering fields, other sciences such as biology and biotechnology, patent law, business, marketing, computer science, chemical information, public speaking, and writing. Minors and electives can be most helpful if you have a particular career in mind. If this is the case, determine the educational requirements by talking with people currently in these careers. You can sometimes find these individuals through your college alumni office or through your local ACS section. Chemists with advanced chemistry degrees usually begin their careers with more specialized responsibilities than bachelor's degree chemists. They usually work in research or as college or university faculty members. Many of these positions are only open to M.S. and Ph.D. chemists.

Industry Private industry employs about two-thirds of all chemists. Private industry offers excellent salaries and benefits and many different career paths for chemists. Most industrial chemists work in research and development (R&D), R&D management, sales, or marketing. Entry-level bachelor's degree chemists may work in research or plant labs analyzing and testing products. They may also work with senior researchers in R&D laboratories. As they gain experience, they work more independently and can advance to supervisory positions or change career

tracks to work in chemical sales or other business functions. Continuing education greatly aids changing career tracks. Taking a minor in business or marketing can aid bachelor degree chemists in beginning their careers with a sales or marketing job.

Government Federal, state, and local government units employ many chemists. About 10% of all chemists are employed by the government. Government salaries often are lower than in private industry, particularly starting salaries. However, the gap has narrowed in recent years. Despite government cutbacks, jobs remain more secure in government than in private industry. Chemists are the largest group of scientists working for the federal government. Many work for large research laboratories such as the National Institutes of Health and the Naval Research Laboratory. Others work for Federal government departments such as Energy, Defense, Interior, Agriculture, Commerce, Health and Human Services, and Justice. There they may do basic or applied research. Much of this work is aimed at developing the scientific basis for government regulations. Chemists also perform testing work needed to enforce government regulations and monitor their effectiveness. Chemists are also responsible for administering government funding to universities and research institutes. Other chemists work as program administrators within government. Chemists also work writing and editing government regulations and other documents. "Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

Academia Academia includes primary and secondary schools, community colleges, four-year colleges, and universities. Teaching in academia often involves teaching other sciences besides chemistry. Teaching in primary and junior high school often involves teaching young people the scientific method and the role of science in health and the environment. Thinking back on your own pre-college education, you'll realize that, in addition to teaching a subject such as science, teachers also counsel and discipline students. They prepare examinations, meet with and advise parents, and work with other teachers and administrators to keep the school running smoothly. It is to fulfill these responsibilities that states require teacher certification.

Due to a shortage of science teachers, many school districts are hiring B.S. or B.A. chemists to teach provided they take the necessary courses required to obtain a teaching certificate. These courses usually can be taken in the evening, weekends, or the summers. Each department of education in each state specifies the courses needed for certification. These are uniform for all the school districts in a given state. However, the courses required vary from state to state. Contact your local school district to find out what courses you would need to complete to be certified as a teacher in your state. Remember, requirements vary from state to state. So if you plan to move after graduation, determine the certification requirements in your new state. Secondary School Teaching - Chemistry teachers in secondary (high) schools often teach other science courses such as general science, physics, math, and biology. These teachers often enjoy the satisfaction of having students choose careers in science and engineering as a result of their experiences in secondary school science courses. To teach in public school, one must take the necessary education courses to obtain a teaching certificate in addition to courses in your major discipline. Many private/parochial schools do not require a teaching certificate; however, they frequently pay less than public schools. After you begin your teaching career, you will find that additional courses, often culminating in a master's degree, will improve your promotion prospects, job security, marketability. This is particularly true for secondary school teachers. Depending on your career goals, the courses you take may be primarily chemistry courses or education courses. You may also find it advantageous to broaden your skills beyond that of science taking the courses necessary to become certified in other field. College and University Teaching - Chemistry faculty members teach chemistry courses, prepare and grade exams, counsel students (often providing career advice), and participate in chemistry department and college governance. At four-year institutions and universities with graduate schools (research universities), research plays a major role. In addition to the responsibilities listed previously, chemistry faculty members must design and execute a

creative research program. To do this, they must obtain research funding by writing grant proposals, persuade students to work with them as bench researchers, and supervise and guide these students in their research while allowing them sufficient independence to develop as creative chemists in their own right. Writing successful grant proposals is critical to career success for faculty members at research universities and some four-year institutions. Successful graduate school and post-doctoral research is helpful. So is one's previous "Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

success in independent research. This success is usually measured by both the number and quality of one's publications in chemistry journals. However, the ability to organize your thoughts and write clearly and well is also critical in preparing successful grant proposals. The ability to present oral research papers at conferences and seminars at other universities is also important in developing a good professional reputation that may influence grant proposal reviewers in your favor. Community College Teaching - At two-year colleges, the primary emphasis is on teaching, not research. Faculty members may hold either Ph.D. or MS degrees. The fraction of faculty members holding Ph.D. degrees is increasing as the academic job market becomes ever more competitive. Tenure is offered at most, but not all, two-year colleges. Normally it is awarded after two to five years of probationary employment. While any research the faculty member accomplishes will be a positive factor in tenure evaluations, the primary emphasis is on teaching. Usually the facilities for doing research are very limited in four- year colleges. However, summer National Science Foundation programs and other opportunities exist give community college faculty members access to first-rate research facilities. Many twoyear colleges offer part-time positions teaching courses during the day as well as the evening. Although the pay is often low and part-time employees do not receive fringe benefit, these adjunct positions are very useful in gaining the experience needed for obtaining fulltime, tenure track positions in 2-year and 4-year colleges and provide opportunities for chemists to

combine teaching with another job, education, or personal commitments such as raising a family. Research - Success in research, measured by research funding obtained for creative projects and publication of interesting results in chemistry journals, is necessary for career success at research universities. This is the major factor in deciding whether to award an assistant professor tenure. Without tenure, chemistry department faculty members are employed under a series of one- to six-year contracts. At one or more times during an assistant professor's first six years at a research university, he or she will be considered for tenure. If the assistant professor does not obtain tenure, a seventh year allows him or her time to obtain another position. Some people in this position, particularly those who are outstanding teachers, obtain positions in four-year institutions or community colleges where research is not emphasized. Others enter industry or obtain non-faculty research staff positions. Research opportunities for chemistry faculty members at community colleges and some four year institutions are more limited. Many who prefer teaching to supervising research find teaching at community colleges more rewarding. These faculty members often teach more courses than their counterparts at research universities.

Nontraditional Careers Chemistry is the springboard for many careers in areas other than the more traditional research laboratory or academic positions. A growing number of chemical scientists at all degree levels are pursuing careers at chemistry interfaces. Professionals use their training in chemistry to launch careers in, for example, law, business management, journalism, and computer science. They make broad use of scientific knowledge in these career areas. "Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

Earnings New chemistry graduates starting salaries' vary depending on a number of factors and one o the most important is where they work. According to the ACS 2004 Starting Salary Survey, the

median annual salary of inexperienced bachelor's chemistry graduates working full time for the class of 2004 was $33,000. For inexperienced master's graduates employed in industry, the median salary was $44,500, and for inexperienced Ph.D.s, the median annual salary was $72,500. (Inexperienced is defined as having less than one year of technical work experience prior to graduation.) Starting salaries for new and inexperienced graduates employed full-time in an academic setting were noticeably lower. For the new bachelor's chemists in this sector the median salary in 2004 was $30,100. For inexperienced master's graduates employed in academia, the median salary was $40,500, and for inexperienced Ph.D.s, the median annual salary was $43,260. In addition, the 2005 census of all ACS members in the workforce reveals lower unemployment and shifts in the chemical profession. The gain for bachelor's chemists this year was from $61,000 to $64,000 or 4.9%; for master's, from $71,000 to $75,000, or 5.6%; and for Ph.D.s, from $90,000 to $93,800, or 4.2%. The salary gain for chemists as a whole was, as would be expected, more modest. Salaries rose from the median of $82,000 for all 2004 survey respondents to $83,000 for this year's respondents. The full report may be viewed at www.careercornerstone.org/chemistry/2005salary.pdf. Findings from the class of 2004 are summarized in Chemical and Engineering News. A full report of the Starting Salary Survey is available from the American Chemical Society at www.chemistry.org/careers or by calling ACS's Office of Society Services at 1-800-2275558. "Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

Job Hunting Advice Your career as a professional chemist begins with your first job. You should begin your job hunt about a year before graduation by assembling a list of companies you would like to work for and people at each company to contact. The summer before your final year is a good time to start. Plan to visit a local library to obtain information on potential employers. Also read at

least one good book on job hunting techniques. The ACS publishes several brochures tailored for chemists and engineers to help you write your resume and cover letter and interview more effectively. These are listed in the final section of this brochure. To obtain advice in your job hunt, consult with people at your campus placement center. Most placement centers arrange on-campus interviews with corporate recruiters visiting your school. They can also provide guidance in writing your r‚sum‚ and cover letter. In addition, they can provide counseling and moral support. Also discuss your job hunting and career concerns with professors, particularly faculty advisors. Finding a job is seldom easy. Disappointment is common in job hunting. Competition is stiff and so you should not become discouraged if you do not succeed in getting a particular position. You must expect to apply for many positions to win a few interviews. Not every interview will result in getting a job offer.

Leads Begin looking for job leads after you have decided what type (or types) of job you want, what type of working environment you prefer, and what your geographic limitations (if any) are. You can identify job leads by: • Checking with your campus placement office to determine what corporate recruiters will be visiting campuses and when. Your placement office will have publications such as "The Job Choices Annual" which provides information on many companies, what types of job openings they have, and the personnel manager's name and address. • Consulting with family, friends, and faculty members for the names and telephone numbers of professionals in the field of chemistry you are interested in or working for companies you might want to work for. Don't neglect recent chemistry graduates from your school. In addition to job leads, they can provide helpful, up-to-date job-hunting tips. • Checking newspapers, telephone "Yellow Pages," and chambers of commerce listings for possible job leads. • Checking the Internet. There are many job sites listed on the World Wide Web. You can locate many of these sites by typing a keyword such as "employment" on your search engine. Don't neglect the home pages of companies you would like to work for. These provide useful information on the company and its products. Many company home pages also list job openings. Job opening information is also available on the home pages of

professional organizations such as the ACS. Some publications such as the "National Business Employment Weekly" have helpful articles on job-hunting topics on their websites. • Visiting your library and reviewing publications such as "Peterson's Guide," "Dun and Bradstreet," "The Thomas Register," and "Moody's Industries" for general descriptions of various corporations. Also, consult books on writing resumes and cover letters and employment interviewing while you are in the library. • Using ACS services, particularly those of the ACS Employment Aids Office. This office maintains the Employment Clearing House -- a collection of resumes that employers can "Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

access through ACS. This service is free to ACS members and student affiliates. Contact the Employment Aids Office to have your resume included. • Accessing the ACS website. The employment advertisements and the Younger Chemists Committee web page are particularly useful to job hunters. • Registering for the Employment Clearing House at ACS national and regional meetings. Through the clearing house, you can arrange interviews during the meeting with prospective employers. This service is free to those registered at the meeting. • Participating in other job-hunting related activities at ACS meetings. These include mock interviews, resume consultations with ACS experts, and workshops and symposia on jobhunting topics. • Taking out an advertisement in the "Situations Wanted" section of Chemical & Engineering News. ACS offers reduced rates to members and student affiliates. • Consult your college or university Web page to find job banks, resume writing, interviewing, and networking assistance.

Resumes It is best to prepare your resume during the summer before your senior year. You'll have more leisure consider what types of jobs you would like and to assemble the information on your qualifications and accomplishments. You can also request permission of the individuals you would like to list as references. Your resume is the first example prospective employers have of your communications skills. So it should be well-organized and well-written. Your resume

should outline your experience, interests, abilities, and goals and should emphasize your accomplishments. Limit your resume to one page but make it as comprehensive as possible. You can list publications and references on a second page. Reference books at your library or placement office can provide models of resume content and format. Your format should contribute to the clarity and readability of your resume. If you are uncertain about year career goals, prepare a separate resume tailored for each career goal. For example, you might prepare one version for the petrochemical industry and one for the pharmaceutical industry. The resume you target to pharmaceutical industry could emphasize your interest in biochemistry and the biochemistry courses you took. Your second resume could emphasize courses more relevant to the petrochemical industry such as physical chemistry and catalysis chemistry courses. Your cover letter should be more than just a note saying, "Here is my resume." Also it shouldn't be just a restatement of what is in your resume. Your resume tells what you are: a graduating chemistry student with certain experience, abilities, and accomplishments. Your cover letter should tell employers who you are through both its content and tone. It should demonstrate that you are a productive, accomplishment-oriented individual with good written communications skills. Like your resume, it should be one page long.

Interviews Your resume and cover letter will get you an employment interview; they won't get you a job offer. The critical step in getting a job offer is the employment interview. Expect some nervousness and anxiety as you approach this critical step in your job hunt. Preparation and practice can reduce your concerns. Begin preparing by reviewing your resume thoroughly so you will not need to refer to it during your interview. "Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

References Any successful job search entails an extensive examination of self, employer, and the market. Job candidates should always research information about prospective companies before any

interview. Recruiters are most impressed with candidates who have some prior knowledge of the company. Ironically, this research is most commonly ignored or omitted by candidates when preparing for an interview. Do not allow the resources found in the data file below to limit you. It is not an exhaustive list of all resources available. However, it is a list widely used by chemists, chemical engineers, and counselors to seek out information on career-related topics.

Overcoming Challenges Everyone will face challenges as they transition from high school to college to the work place. Women and minorities may face additional challenges. Organizations and publications offer support and resources to these chemistry students.

Minorities Minorities are the fastest growing part of the U.S. population, and in the next century, they will become the majority possessing both the clout and talent to contribute significantly to the nation's future. Minorities are underrepresented in the sciences. The ACS, the world's largest scientific society, has committed to reach out and invite underserved minorities to participate in the excitement and opportunities that literacy in the sciences offer and execute this commitment through its Minority Affairs Program. The mission of the minority affairs program is to conceive, develop, coordinate, and implement programs that are designed to encourage and support minority involvement in the chemical sciences.

People with Disabilities Misconceptions have an unfortunate effect in deterring young people with physical and learning disabilities from careers in science. Well-meaning but uninformed parents, teachers, college admissions personnel, and others imply or state that science is unsuitable as a career for a person with a disability. They encourage bright, enthusiastic high school students to avoid chemistry labs out of concern that mobility aids-- or speech, hearing, or visual impairments will represent undue safety risks or interfere with traditional teaching methods. An extensive report by Anne Swanson and Norman Steere, published in the Journal of Chemical Education

in 1981, found no basis for this concern. It indicated that people with disabilities pose no greater safety hazard in the classroom, laboratory, or workplace than their able-bodied peers. Few require any special pedagogical techniques. A 1995 study by the American Council on Education (ACE) indicated that college freshmen with disabilities have just as great an interest in a science major as other students. The American Chemical Society and its Committee on Chemists with Disabilities published Working Chemists with Disabilities: Expanding Opportunities in Science to address these misconceptions and increase opportunities for people with disabilities in chemistry and other fields of science. Assistive technologies and legislation already have eliminated many real barriers. Some of the most serious remaining impediments are not physical, but attitudinal. "Chemistry Overview" Prepared as part of the Sloan Career Cornerstone Center (www.careercornerstone.org) Source: "Careers for Chemists" © American Chemical Society

Professional Organizations Professional organizations and associations provide a wide range of resources for planning and navigating a career in Chemistry. These groups can play a key role in your development and keep you abreast of what is happening in your area of specialization. Most maintain a website and many of the associations have special pages for high school and/or college students with questions about careers in the field. Associations promote the interests of their members and provide a network of contacts that can help you find jobs and move your career forward. They can offer a variety of services including job referral services, continuing education courses, insurance, travel benefits, periodicals, and meeting and conference opportunities. Some of these organizations have special interest in issues related to women or underrepresented minority groups. The following is a partial list of professional associations serving the field of chemistry. A broader list of professional associations, including those specifically serving women and minority groups is also available by clicking here including the Association for Women in Science, the American Indian Science and Engineering Society, and the Vietnamese Association for Computing, Engineering Technology, and Science. American Chemical Society (www.acs.org) The American Chemical Society is a self-governed individual membership organization that

consists of more than 158,000 members at all degree levels and in all fields of chemistry. The organization provides a broad range of opportunities for peer interaction and career development, regardless of professional or scientific interests. The programs and activities conducted by ACS today are the products of a tradition of excellence in meeting member needs that dates from the Society's founding in 1876. American Chemistry Council (www.americanchemistry.com) Represents the American chemical industry. Information about the Responsible Care initiative, news articles, press releases, research and testing, and public health. International Council of Chemical Associations (www.icca-chem.org) International Council of Chemical Associations (ICCA) is the world-wide voice of the chemical industry, representing chemical manufacturers and producers all over the world. It accounts for more than 75 per cent of chemical manufacturing operations with a production exceeding USD 1,6 trillion annually. Almost 30 percent of this production is traded internationally. ICCA promotes and co-ordinates Responsible Care and other voluntary chemical industry initiatives. European Federation of Chemical Engineering (www.dechema.de/efce.htm) Since 1953 the European Federation of Chemical Engineering has promoted scientific

collaboration and supported the work of engineers and scientists in 28 European countries.

Moreover, from the very beginning Eastern and Central European countries were included. Today the EFCE represents more than 100,000 chemical engineers in Europe. With its 22 Working Parties and 3 Sections it covers all areas of Chemical Engineering. Institution of Chemical Engineers (www.icheme.org) The Institution of Chemical Engineers (IChemE) is the professional body for chemical and process engineers. Originally founded in 1922, IChemE has grown continuously to its current status as a leading engineering organization with an international membership across more than 80 countries approaching 25,000.