Hydrogen peroxide
14403
226087920
2008-07-16T19:44:42Z
128.143.230.1
{{Chembox new
| Name = Hydrogen peroxide
| ImageFileL1 = Hydrogen-peroxide-2D.png
| ImageNameL1 = Structural formula of hydrogen peroxide
| ImageSizeL1 = 120px
| ImageFileR1 = Hydrogen-peroxide-3D-balls.png
| ImageNameR1 = Ball-and-stick model of the hydrogen peroxide molecule
| ImageSizeR1=120px
| IUPACName = Hydrogen peroxide
| OtherNames = μ-1κO,2κO’-Dioxidodihydrogen<br />Dihydrogen dioxide<br />Hydrogen dioxide<br />Dioxidane
| Section1 = {{Chembox Identifiers
| CASNo = 7722-84-1
| RTECS = MX0900000
}}
| Section2 = {{Chembox Properties
| Formula = H<sub>2</sub>O<sub>2</sub>
| MolarMass = 34.0147 g·mol·<sup>−1</sup>.
| Appearance = Very pale blue color; colorless in solution
| Density = 1.1 g/cm<sup>3</sup>, liquid (approximate)
| Solubility = [[Miscible]]
| MeltingPt = -11 °C (262.15 K)
| BoilingPt = 150.2 °C (423.35 K)
| pKa = 11.65
| Viscosity = 1.245 c[[Poise|P]] at 20 °C
| Dipole = 2.26 [[Debye|D]]
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS = [http://www.bu.edu/es/labsafety/ESMSDSs/MSHydPeroxide.html 30% hydrogen peroxide msds]<br />[http://www.h2o2.com/intro/FMC_MSDS_40_to_60.pdf 60% hydrogen peroxide msds]
| MainHazards = Oxidant, corrosive
| NFPA-H = 3 | Reactivity=1 | Other=OX
| NFPA-F =
| NFPA-R = 1
| NFPA-O = ox
| FlashPt = Non-flammable
| RPhrases = {{R5}}, {{R8}}, {{R20}}, {{R22}}, {{R35}}
| SPhrases = {{(S1)}}, {{(S2)}}, {{S17}}, {{S26}}, {{S28}}, {{S36}}, {{S37}}, {{S39}}, {{S45}}
}}
| Section8 = {{Chembox Related
| OtherCpds = [[water (molecule)|Water]]<br />[[Ozone]]<br />[[Hydrazine]]
}}}}
'''Hydrogen peroxide''' (H<sub>2</sub>O<sub>2</sub>) is a very pale blue liquid which appears colorless in a dilute solution, slightly more [[viscous]] than water. It is a weak [[acid]]. It has strong [[oxidation|oxidizing]] properties and is therefore a powerful [[bleaching agent]] that is mostly used for bleaching paper, but has also found use as a [[disinfectant]], as an [[oxidizer]], as an [[antiseptic]], and in [[rocket]]ry (particularly in high concentrations as ''[[high-test peroxide]]'' or ''HTP'') as a [[monopropellant]], and in [[bipropellant]] systems. {{Fact|date=February 2008}} The oxidizing capacity of hydrogen peroxide is so strong that the chemical is considered a highly [[reactive oxygen species]].
Hydrogen peroxide is naturally produced as a byproduct of oxygen metabolism, and virtually all organisms possess enzymes known as [[peroxidase]]s, which harmlessly catalytically decompose low concentrations of hydrogen peroxide to water and oxygen (''see [[#Decomposition|Decomposition]] below'').
==History==
Hydrogen peroxide was first isolated in 1818 by [[Louis Jacques Thénard]] by reacting [[barium peroxide]] with [[nitric acid]].<ref>{{cite journal
| title =
| author = L. J. Thenard
| journal = [[Annales de chimie et de physique]]
| volume = 8
| year =1818
| pages = 308}}</ref> An improved version of this process used [[hydrochloric acid]], followed by [[sulfuric acid]] to precipitate the [[barium sulfate]] byproduct. Thénard's process was used from the end of the 19th century until the middle of the 20th century.<ref>C. W. Jones, J. H. Clark. ''Applications of Hydrogen Peroxide and Deriatives''. Royal Society of Chemistry, '''1999'''.</ref> Modern production methods are discussed below.
For a long time it was believed that pure hydrogen peroxide was unstable, because attempts to separate the hydrogen peroxide from the water, which is present during synthesis, failed. This was because traces of solids and [[Heavy metals|heavy metal]] [[ion]]s led to a catalytic decomposition or explosions of the hydrogen peroxide. 100% pure hydrogen peroxide was first obtained through [[vacuum distillation]] by [[Richard Wolffenstein (chemist)|Richard Wolffenstein]] in 1894.<ref>{{cite journal
| title = Concentration und Destillation von Wasserstoffsuperoxyd
| author = [[Richard Wolffenstein (chemist)|Richard Wolffenstein]]
| journal = Berichte der deutschen chemischen Gesellschaft
| volume = 27
| issue = 3
| pages = 3307–3312
| year = 1894
| url =
| doi = 10.1002/cber.189402703127}}</ref>
==Uses==
===Industrial applications===
About 50% of the world's production of hydrogen peroxide in 1994 was used for pulp- and paper-bleaching.<ref name=HageLienke>{{cite journal
| journal = Angewandte Chemie International Edition
| title = Applications of Transition-Metal Catalysts to Textile and Wood-Pulp Bleaching
| author = Ronald Hage, Achim Lienke
| volume = 45
| issue = 2
| year = 2005
| doi = 10.1002/anie.200500525
| pages = 206–222}}</ref> Other bleaching applications are becoming more important as hydrogen peroxide is seen as an environmentally benign alternative to [[chlorine]]-based bleaches. It is highly corrosive to metal.
Other major industrial applications for hydrogen peroxide include the manufacture of [[sodium percarbonate]] and [[sodium perborate]], used as mild bleaches in [[laundry]] [[detergent]]s. It is used in the production of certain [[organic peroxide]]s such as [[dibenzoyl peroxide]], used in [[Radical polymerization|polymerisations]] and other chemical processes. Hydrogen peroxide is also used in the production of [[epoxide]]s such as [[propylene oxide]]. Reaction with [[carboxylic acid]]s produces a corresponding [[peroxy acid]]. [[Peracetic acid]] and [[meta-chloroperoxybenzoic acid]] (commonly abbreviated mCPBA) are prepared from [[acetic acid]] and ''meta''-chlorobenzoic acid, respectively. The latter is commonly reacted with [[alkene]]s to give the corresponding [[epoxide]].
In the PCB manufacturing process, hydrogen peroxide mixed with sulfuric acid was used as the microetch chemical for copper surface roughening preparation.
A combination of a powdered precious metal-based catalyst, hydrogen peroxide, methanol and water can produce superheated steam in one to two seconds, releasing only [[carbon dioxide|CO<sub>2</sub>]] and high temperature steam for a variety of purposes.<ref>The Society Of Chemical Industry article (Google cached article) re: new hydrogen peroxide/methyl alcohol catalyst[http://64.233.183.104/search?q=cache:1lgZX4TmL0MJ:www.soci.org/SCI/general/2007/html/ge630.jsp+%22Portable,+superheated,+high+pressure+steam+that+could+be+used+in+applications%22&hl=en&ct=clnk&cd=1]</ref>.
===Domestic uses===
* Diluted H<sub>2</sub>O<sub>2</sub> (around 15%) is used to bleach human [[hair]], hence the phrase "peroxide blonde". It is absorbed by skin upon contact and creates a local skin [[capillary]] [[embolism]] which appears as a temporary whitening of the skin. It is used to whiten bones that are to be put on display. The strength of a solution may be described as a percentage or volume, where 1% hydrogen peroxide releases 3.3 volumes of oxygen during decomposition.Thus, a 3% solution is equivalent to 10 volume and a 6% solution to 20 volume, etc.
* 3% H<sub>2</sub>O<sub>2</sub> is used medically for cleaning wounds, removing dead tissue, and as an oral [[debridement|debriding]] agent. Peroxide stops slow (small vessel) wound bleeding/oozing, as well. Most over-the-counter peroxide solutions are not suitable for ingestion.
* 3% H<sub>2</sub>O<sub>2</sub> is effective at treating fresh (red) blood-stains in clothing and on other items. It must be applied to clothing before blood stains can be accidentally "set" with heated water. Cold water and soap are then used to remove the peroxide treated blood.
* The United States [[Food and Drug Administration]] (FDA) has classified hydrogen peroxide as a Low Regulatory Priority (LRP) drug for use in controlling fungus on fish and fish eggs. (See [[ectoparasite]].)
* Some gardeners and users of [[hydroponics]] advocate the use of hydrogen peroxide in watering solutions. They claim that its spontaneous decomposition releases oxygen that enhances a plant's root development and helps to treat [[root rot]] (cellular root death due to lack of oxygen).
* Laboratory tests conducted by fish culturists in recent years have demonstrated that common household hydrogen peroxide can be used safely to provide oxygen for small fish.<ref>[http://www.great-lakes.org/Wkly_news/07-07-03.html#Oxygen Great-lakes.org]</ref><ref>[http://www.fws.gov/midwest/ashland/mtan/mtan_35.html#Guide%20to%20Drug,%20Vaccine,%20and%20Pesticide%20Use%20in%20Aquaculture fws.gov]</ref> Hydrogen peroxide releases oxygen by decomposition when it is exposed to [[catalysts]] such as [[manganese dioxide]].
* Hydrogen peroxide is a strong oxidizer effective in controlling sulfide and organic related odors in wastewater collection and treatment systems. It is typically applied to a wastewater system where there is a retention time of 30 minutes to 5 hours before hydrogen sulfide is released. Hydrogen peroxide oxidizes the hydrogen sulfide and promotes bio-oxidation of organic odors. Hydrogen peroxide decomposes to oxygen and water, adding dissolved oxygen to the system thereby negating some Biological Oxygen Demand (BOD).
* Mixed with baking soda and a small amount of hand soap, hydrogen peroxide is effective at removing [[skunk]] odor. <ref>Chemist Paul Krebaum claims to have originated the formula for use on skunked pets at [http://home.earthlink.net/~skunkremedy/home/ Skunk Remedy]</ref>
* Hydrogen peroxide is used with [[phenyl oxalate ester]] and an appropriate [[dye]] in [[glow stick]]s as an [[oxidizing agent]]. It reacts with the ester to form an unstable CO<sub>2</sub> [[dimer]] which excites the dye to an [[excited state]]; the dye emits a [[photon]] (light) when it [[spontaneous emission|spontaneously relaxes]] back to the [[ground state]].
* Dilute hydrogen peroxide can be used in a 50/50 mixture with white vinegar in the removal of accumulated lead and gun powder from a stainless steel firearm suppressor. The acetic acid is the main reagent, but the bubbling action of the hydrogen peroxide is used to agitate the mixture and accelerate the reaction. The chemical mixture should be replaced every 24 hours as it will become ineffective after that period. The responsible care of the used chemistry is required as the end result is an aqueous solution of [[lead acetate]], which is highly toxic and must be disposed of through a Hazardous Waste facility. This method should not be used on aluminum suppressors, as acetic acid will dissolve the aluminum and form aluminum acetate.{{Fact|date=June 2008}}
===Storage===
Regulations vary, but low concentrations, such as 3%, are widely available and legal to buy for medical use. Higher concentrations may be considered hazardous and are typically accompanied by a [[Material Safety Data Sheet]] (MSDS). In high concentrations, hydrogen peroxide is an aggressive oxidizer and will corrode many materials, including human skin. In the presence of a [[reducing agent]], high concentrations of H<sub>2</sub>O<sub>2</sub> will react violently.
Hydrogen peroxide should be stored in a cool, dry, well-ventilated area and away from any flammable or combustible substances.<ref>[http://www.bu.edu/es/labsafety/ESMSDSs/MSHydPeroxide.html Hydrogen Peroxide MSDS]</ref> It should be stored in a container composed of non-reactive materials such as stainless steel or glass (other materials including some plastics and aluminium alloys may also be suitable).<ref>[http://www.ozoneservices.com/articles/004.htm Ozonelab Peroxide compatibility]</ref> Because it breaks down quickly when exposed to light, it should be stored in an opaque container, and pharmaceutical formulations typically come in brown bottles that filter out light.<ref>{{cite web|url = http://www.truthorfiction.com/rumors/h/hydrogen-peroxide.htm |title = The Many Uses of Hydrogen Peroxide-Truth! Fiction! Unproven! |accessdate = 2008-06-30}}</ref>
===Use as propellant===
H<sub>2</sub>O<sub>2</sub> can be used either as a [[monopropellant]] (not mixed with fuel) or as the oxidizer component of a [[bipropellant rocket]]. Use as a monopropellant takes advantage of the decomposition of 70–98+% concentration hydrogen peroxide into steam and oxygen. The propellant is pumped into a reaction chamber where a catalyst, usually a silver or platinum screen, triggers decomposition, producing steam at over 600 °C which is expelled through a [[nozzle]], generating [[thrust]]. H<sub>2</sub>O<sub>2</sub> monopropellant produces a maximum [[specific impulse]] (''I''<sub>sp</sub>) of 161 s (1.6 [[newton-second|kN·s]]/kg), which makes it a low-performance monopropellant. Peroxide generates much less thrust than [[hydrazine]], but is not [[toxic]]. The [[Bell Rocket Belt]] used hydrogen peroxide monopropellant.
As a bipropellant H<sub>2</sub>O<sub>2</sub> is decomposed to burn a fuel as an oxidizer. Specific impulses as high as 350 s (3.5 kN·s/kg) can be achieved, depending on the fuel. Peroxide used as an oxidizer gives a somewhat lower ''I''<sub>sp</sub> than liquid oxygen, but is dense, storable, noncryogenic and can be more easily used to drive gas turbines to give high pressures. It can also be used for regenerative cooling of rocket engines. Peroxide was used very successfully as an oxidizer in World-War-II German rockets (e.g. [[T-Stoff]] for the [[Me-163]]), and for the low-cost British [[Black Knight (rocket)|Black Knight]] and [[Black Arrow]] launchers. <!--{{cite web
| url = http://www.cue-dih.co.uk/aerospace/aeropdfs/htp_for_prop.pdf
| title = Hydrogen Peroxide for Power and Propulsion}}-->
In the 1940s and 1950s the [[Hellmuth Walter|Walter]] [[gas turbine|turbine]] used hydrogen peroxide for use in [[submarine]]s while submerged; it was found to be too noisy and require too much maintenance compared to [[diesel-electric]] power systems. Some [[torpedo]]es used hydrogen peroxide as oxidizer or propellant, but this was dangerous and has been discontinued by most [[navy|navies]]. Hydrogen peroxide leaks were blamed for the sinkings of [[HMS Sidon (P259)|HMS ''Sidon'']] and the [[Russian submarine Kursk|Russian submarine ''Kursk'']]. It was discovered, for example, by the Japanese Navy in torpedo trials, that the concentration of H<sub>2</sub>O<sub>2</sub> in right-angle bends in HTP pipework can often lead to explosions in submarines and torpedoes. SAAB Underwater Systems is manufacturing the Torpedo 2000. This torpedo, used by the Swedish navy, is powered by a piston engine propelled by HTP as an oxidizer and [[kerosene]] as a fuel in a bipropellant system<ref>{{cite journal|last=Scott|first=Richard |date=November, [[1997]]|year=1997|title=Homing Instincts|journal=Jane's Navy Steam generated by catalytic decomposition of 80-90 % hydrogen peroxide was used for driving the turbopump turbines of the V-2 rockets, the X-15 rocketplanes, the early Centaur RL-10 engines and is still used on [[Soyuz launch vehicle|Soyuz]] for that purpose to-day. International|url=http://babriet.tripod.com/articles/art_hominginstinct.htm}}</ref>.
While rarely used now as a monopropellant for large engines, small hydrogen peroxide [[attitude control]] [[thruster]]s are still in use on some [[satellite]]s. They are easy to throttle, and safer to fuel and handle before launch than hydrazine thrusters. However, [[hydrazine]] is more often used in spacecraft because of its higher [[specific impulse]] and lower rate of decomposition.
Recently H<sub>2</sub>O<sub>2</sub>/[[propylene]] has been proposed as an approach to inexpensive [[SSTO|Single Stage To Orbit]]: a fuel tank containing propylene has a bladder floating in it containing H<sub>2</sub>O<sub>2</sub>. This combination offers 15% superior I<sub>sp</sub> to O2/RP4 (a [[kerosene]] used as rocket propellant), does not need [[turbine]]s or [[cryogenic]] storage or hardware, and greatly reduces the cost of the booster. The potential of this and other alternative systems is discussed in some detail at [http://www.dunnspace.com/ Dunn Engineering].
===Therapeutic use===
Hydrogen peroxide is ''[[generally recognized as safe]]'' (GRAS) as an [[antimicrobial agent]], an oxidizing agent and for other purposes by the US [[Food and Drug Administration]].<ref>{{cite web|title=Sec. 184.1366 Hydrogen peroxide|publisher=U.S. Government Printing Office via GPO Access|url=http://a257.g.akamaitech.net/7/257/2422/04nov20031500/edocket.access.gpo.gov/cfr_2001/aprqtr/21cfr184.1366.htm|date=[[2001-04-01]]|accessdate=2007-07-07}}</ref>
Hydrogen peroxide has been used as an [[antiseptic]] and anti-bacterial agent for many years due to its oxidizing effect. While its use has decreased in recent years with the popularity of better-smelling and more readily-available over the counter products, it is still used by many hospitals, doctors and dentists in sterilizing, cleaning and treating everything from floors to [[root canal]] procedures.
* Like many oxidative antiseptics, hydrogen peroxide causes mild damage to tissue in open wounds, but it also is effective at rapidly stopping capillary bleeding (slow blood oozing from small vessels in abrasions), and is sometimes used sparingly for this purpose, as well as cleaning.
* Hydrogen peroxide can be used as a toothpaste when mixed with correct quantities of baking soda and salt.<ref>{{cite web|last=Shepherd|first=Steven|publisher=FDA Consumer|title=Brushing Up on Gum Disease|url=http://www.fda.gov/bbs/topics/CONSUMER/CON00065.html|accessdate=2007-07-07}}</ref>
* Hydrogen peroxide and [[benzoyl peroxide]] are sometimes used to treat [[Acne vulgaris|acne]].<ref>{{cite journal|last=Milani|first=Massimo|coauthors=Bigardi, Andrea; Zavattarelli, Marco|year=2003|title=Efficacy and safety of stabilised hydrogen peroxide cream (Crystacide) in mild-to-moderate acne vulgaris: a randomised, controlled trial versus benzoyl peroxide gel|url=http://www.ingentaconnect.com/content/libra/cmro/2003/00000019/00000002/art00010|journal=Current Medical Research and Opinion|volume=19|issue=2|pages=135–138(4)|doi=10.1185/030079902125001523}}</ref>
* Hydrogen peroxide is used as an [[emetic]] in veterinary practice.<ref>{{cite encyclopedia|title=Drugs to Control or Stimulate Vomiting|encyclopedia=Merck Veterinary manual|url=http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/190303.htm|publisher=[[Merck & Co.]], Inc|date=2006}}</ref>
;Alternative uses
* Some people have tried using peroxide as a treatment for cancer. The [[American Cancer Society]] states that "there is no scientific evidence that hydrogen peroxide is a safe, effective or useful cancer treatment", and advises cancer patients to "remain in the care of qualified doctors who use proven methods of treatment and approved clinical trials of promising new treatments." <ref>{{cite journal|title=Questionable methods of cancer management: hydrogen peroxide and other 'hyperoxygenation' therapies |journal=CA: a cancer journal for clinicians|volume=43|issue=1|pages=47–56|year=1993|pmid=8422605|doi=10.3322/canjclin.43.1.47}}</ref>
* Another controversial alternative medical procedure is [[inhalation]] of hydrogen peroxide at a concentration of about 1%. Internal use of hydrogen peroxide has a history of causing fatal [[blood disorder]]s, and its recent use as a therapeutic treatment has been linked to several deaths.<ref>{{cite news|last=Cooper|first=Anderson|title=A Prescription for Death?|publisher=CBS News|date=[[2005-01-12]]|url=http://www.cbsnews.com/stories/2005/01/12/60II/main666489.shtml|accessdate=2007-07-07}}</ref><ref>{{cite web|last=Mikkelson|first=Barbara|title=Hydrogen Peroxide|url=http://www.snopes.com/medical/healthyself/peroxide.asp|publisher=Snopes.com|date=[[2006-04-30]]|accessdate=2007-07-07}}</ref>
==Physical properties==
[[Image:H2O2 structure.png|500px|Structure of hydrogen peroxide]]
While the [[Linear alkane conformation|anti conformer]] would minimize steric repulsions, a 90° torsion angle would optimize mixing between the filled ''p-type'' orbital of the oxygen (one of the lone pairs) and the [[LUMO]] of the [[vicinal]] O-H bond.<ref>{{cite book|last=Dougherty|first=Dennis A.|coauthors=Eric V. Anslyn |title=Modern Physical Organic Chemistry |publisher=University Science |location= |year=2005 |pages=122|isbn=1-891389-31-9 |oclc= |doi=}}</ref> Reflecting a compromise between the two interactions, gaseous and liquid hydrogen peroxide adopts an [[Linear alkane conformation|anticlinal]] "skewed" shape. This rotational conformation is a compromise between the ''anti'' conformer, which would minimize steric repulsion, and between the ''syn'' conformer that associates O-H bonds with [[lone pair]]s on the oxygen atoms. Despite the fact that the O-O bond is a single bond, the molecule has a remarkably high barrier to complete rotation of 29.45 [[Kilojoule|kJ]]/[[Mole (chemistry)|mol]] (compared with 12.5 kJ/mol for the rotational barrier of [[ethane]]). The increased barrier is also attributed to repulsion between one lone pair and other lone pairs. The [[Molecular geometry|bond angles]] are affected by [[hydrogen bonding]], which is relevant to the structural difference between gaseous and [[crystalline]] forms; indeed a wide range of values is seen in crystals containing molecular H<sub>2</sub>O<sub>2</sub>.
==Chemical properties==
H<sub>2</sub>O<sub>2</sub> is one of the most powerful oxidizers known -- stronger than [[chlorine]], [[chlorine dioxide]], and [[potassium permanganate]]. Also, through catalysis, H<sub>2</sub>O<sub>2</sub> can be converted into hydroxyl radicals (.OH) with reactivity second only to fluorine.
{| class="wikitable"
! [[Oxidant]]
! [[Oxidation]] potential, V
|-
| [[Fluorine]]
| 3.0
|-
| [[Hydroxyl]] radical
| 2.8
|-
| [[Ozone]]
| 2.1
|-
| Hydrogen peroxide
| 1.8
|-
| [[Potassium permanganate]]
| 1.7
|-
| [[Chlorine dioxide]]
| 1.5
|-
| [[Chlorine]]
| 1.4
|}
Hydrogen peroxide can decompose spontaneously into water and oxygen. It usually acts as an [[Redox|oxidizing agent]], but there are many reactions where it acts as a [[Redox|reducing agent]], releasing oxygen as a by-product.
It also readily forms both inorganic and organic [[peroxide]]s.
===Decomposition===
Hydrogen peroxide always decomposes (disproportionates) [[exothermic reaction|exothermically]] into [[water (molecule)|water]] and [[oxygen]] gas [[Spontaneous process|spontaneously]]:
:2 H<sub>2</sub>O<sub>2</sub> → 2 H<sub>2</sub>O + O<sub>2</sub>
This process is very favorable thermodynamically. It has a [[Standard enthalpy change of reaction|Δ''H''<sup><s>o</s></sup>]] of −98.2 [[Kilojoule|kJ]]·[[Mole (chemistry)|mol]]<sup>−1</sup> and a [[Gibbs free energy|Δ''G''<sup><s>o</s></sup>]] of −119.2 kJ·mol<sup>−1</sup> and a ΔS of 70.5 J·mol<sup>−1</sup>·K<sup>−1</sup>. The rate of decomposition is dependent on the temperature and concentration of the peroxide, as well as the [[pH]] and the presence of impurities and stabilizers. Hydrogen peroxide is incompatible with many substances that [[catalyse]] its decomposition, including most of the [[transition metal]]s and their compounds. Common catalysts include [[manganese dioxide]], and [[silver]]. The same reaction is catalysed by the [[enzyme]] [[catalase]], found in the [[liver]], whose main function in the body is the removal of toxic byproducts of [[metabolism]] and the reduction of [[oxidative stress]]. The decomposition occurs more rapidly in [[alkali]], so [[acid]] is often added as a stabilizer.
The liberation of oxygen and energy in the decomposition has dangerous side effects. Spilling high concentrations of hydrogen peroxide on a flammable substance can cause an immediate fire, which is further fueled by the oxygen released by the decomposing hydrogen peroxide. High-strength peroxide (also called high-test peroxide, or HTP) must be stored in a suitable,{{Fact|date=February 2007}} vented container to prevent the buildup of oxygen gas, which would otherwise lead to the eventual rupture of the container.
In the presence of certain catalysts, such as Fe<sup>2+</sup> or Ti<sup>3+</sup>, the decomposition may take a different path, with free radicals such as HO· ([[hydroxyl]]) and HOO· being formed. A combination of H<sub>2</sub>O<sub>2</sub> and Fe<sup>2+</sup> is known as [[Fenton's reagent]].
A common concentration for hydrogen peroxide is "20 volume", which means that when 1 volume of hydrogen peroxide is decomposed, it produces 20 volumes of oxygen. A 20 "volume" concentration of hydrogen peroxide is equivalent to 1.67 mol/dm<sup>3</sup> ([[Molar solution]]) or about 6%.
Hydrogen peroxide available at drug stores is three percent solution. In such small concentrations, it is less stable, and decomposes faster. It is usually stabilized with [[acetanilide]], a substance which has toxic side effects in significant amounts.
===Redox reactions===
In aqueous solution, hydrogen peroxide can oxidize or reduce a variety of inorganic ions. When it acts as a reducing agent, [[oxygen]] gas is also produced. In [[acid]] solution Fe<sup>2+</sup> is oxidized to Fe<sup>3+</sup>,
:2 [[Fe]]<sup>2+</sup>(aq) + H<sub>2</sub>O<sub>2</sub> + 2 [[Hydronium|H<sup>+</sup>]](aq) → 2 [[Fe]]<sup>3+</sup>(aq) + 2H<sub>2</sub>O(l)
and [[sulfite]] (SO<sub>3</sub><sup>2−</sup>) is oxidized to [[sulfate]] (SO<sub>4</sub><sup>2−</sup>). However, [[potassium permanganate]] is reduced to Mn<sup>2+</sup> by acidic H<sub>2</sub>O<sub>2</sub>. Under [[alkaline]] conditions, however, some of these reactions reverse; for example, Mn<sup>2+</sup> is oxidized to Mn<sup>4+</sup> (as [[Manganese(IV) oxide|MnO<sub>2</sub>]]).
Another example of hydrogen peroxide acting as a reducing agent is the reaction with [[sodium hypochlorite]], this is a convenient method for preparing [[oxygen]] in the laboratory.
:NaOCl + H<sub>2</sub>O<sub>2</sub> → O<sub>2</sub> + NaCl + H<sub>2</sub>O
Hydrogen peroxide is frequently used as an [[Redox|oxidizing agent]] in organic chemistry. One application is for the oxidation of [[thioether]]s to [[sulfoxide]]s.{{Fact|date=February 2007}} For example, [[methyl phenyl sulfide]] was oxidised to [[methyl phenyl sulfoxide]] in 99% yield in methanol in 18 hours (or 20 minutes using a [[Titanium(III) chloride|TiCl<sub>3</sub>]] catalyst):{{Fact|date=February 2008}}
:Ph-S-CH<sub>3</sub> + H<sub>2</sub>O<sub>2</sub> → Ph-S(O)-CH<sub>3</sub> + H<sub>2</sub>O
Alkaline hydrogen peroxide is used for [[epoxidation]] of electron-deficient alkenes such as [[acrylic acid]]s, and also for oxidation of [[alkylborane]]s to [[alcohol]]s, the second step of [[hydroboration-oxidation]].
===Formation of peroxide compounds===
Hydrogen peroxide is a weak acid, and it can form [[hydroperoxide]] or [[peroxide]] [[salt]]s or derivatives of many metals.
For example, on addition to an aqueous solution of [[chromic acid]] (CrO<sub>3</sub>) or acidic solutions of dichromate salts, it will form an unstable blue peroxide CrO(O<sub>2</sub>)<sub>2</sub>. In aqueous solution it rapidly decomposes to form oxygen gas and chromium salts.
It can also produce peroxoanions by reaction with [[anion]]s; for example, reaction with [[borax]] leads to [[sodium perborate]], a bleach used in laundry detergents:
:Na<sub>2</sub>B<sub>4</sub>O<sub>7</sub> + 4 H<sub>2</sub>O<sub>2</sub> + 2 NaOH → 2 Na<sub>2</sub>B<sub>2</sub>O<sub>4</sub>(OH)<sub>4</sub> + H<sub>2</sub>O
H<sub>2</sub>O<sub>2</sub> converts [[carboxylic acid]]s (RCOOH) into peroxy acids (RCOOOH), which are themselves used as oxidizing agents. Hydrogen peroxide reacts with [[acetone]] to form [[acetone peroxide]], and it interacts with [[ozone]] to form [[hydrogen trioxide]], also known as [[trioxidane]]. Reaction with [[urea]] produces [[carbamide peroxide]], used for whitening teeth. An acid-base adduct with [[triphenylphosphine oxide]] is a useful "carrier" for H<sub>2</sub>O<sub>2</sub> in some reactions.
===Alkalinity===
Hydrogen peroxide is a much weaker [[Base (chemistry)|base]] than water, but it can still form adducts with very strong acids. The [[superacid]] [[Fluoroantimonic acid|HF/SbF<sub>5</sub>]] forms unstable compounds containing the [H<sub>3</sub>O<sub>2</sub>]<sup>+</sup> ion.
==Manufacture==
Hydrogen peroxide is manufactured today almost exclusively by the [[autoxidation]] of [[2-ethyl-9,10-dihydroxyanthracene]] (C<sub>16</sub>H<sub>14</sub>O<sub>2</sub>) to [[2-ethylanthraquinone]] (C<sub>16</sub>H<sub>12</sub>O<sub>2</sub>) and hydrogen peroxide using oxygen from the air. This is known as the Riedl-Pfleiderer process.
[[Image:Riedl-Pfleiderer process.svg|420px|center|Hydrogen peroxide production with the Riedl-Pfleiderer process process]]
In this reaction, the hydroxy groups on the middle ring of [[anthracene]] are deprotonated and are turned into [[ketone]]s, while two double bonds are lost from the middle ring and are replaced as C=O double bonds in the ketone groups. The [[anthraquinone]] derivative is then [[Liquid-liquid extraction|extracted]] out and reduced back to the dihydroxy compound using [[hydrogen]] gas in the presence of a metal [[catalyst]]. The overall equation for the process is deceptively simple:
:H<sub>2</sub> + O<sub>2</sub> → H<sub>2</sub>O<sub>2</sub>
However the economics of the process depend on effective recycling of the quinone and extraction solvents, and of the [[hydrogenation]] [[catalyst]].
Formerly inorganic processes were used, employing the [[electrolysis]] of an aqueous solution of [[sulfuric acid]] or acidic [[ammonium bisulfate]] (NH<sub>4</sub>HSO<sub>4</sub>), followed by [[hydrolysis]] of the peroxydisulfate ((SO<sub>4</sub>)<sub>2</sub>)<sup>2−</sup> which is formed.
In 1994, world production of H<sub>2</sub>O<sub>2</sub> was around 1.9 million [[tonne]]s and grew to 2.2 million in 2006,<ref name=HageLienke/> most of which was at a concentration of 70% or less{{Fact|date=April 2007}}. In that year bulk 30% H<sub>2</sub>O<sub>2</sub> sold for around US $0.54 per [[Kilogram|kg]], equivalent to US $1.50 per kg (US $0.68 per [[pound (mass)|lb]]) on a "100% basis{{Fact|date=April 2007}}".
==Concentration==
Hydrogen peroxide works best as a propellant in extremely high concentrations-- roughly over 70%. Although any concentration of peroxide will generate ''some'' hot gas (oxygen plus some steam), at concentrations above approximately 67%, the heat of decomposing hydrogen peroxide becomes large enough to ''completely'' vaporize ''all'' the liquid at standard temperature. This represents a safety and utilization turning point, since decomposition of any concentration ''above'' this amount is capable of transforming the liquid ''entirely'' to heated gas (the higher the concentration, the hotter the resulting gas). This very hot steam/oxygen mixture can then be used to generate maximal thrust, power, or work, but it also makes explosive decomposition of the material far more hazardous.
Normal propellant grade concentrations therefore vary from 70 to 98%, with common grades of 70, 85, 90, and 98%. Many of these grades and variations are described in detail in the United States propellant specification number MIL-P-16005 Revision F, which is currently available. The available suppliers of high concentration propellant grade hydrogen peroxide are generally one of the large commercial companies which make other grades of hydrogen peroxide; including [[Solvay|Solvay Interox]], [[FMC]], [[Degussa]] and [http://www.peroxidepropulsion.com/ Peroxide Propulsion]. Other companies which have made propellant grade hydrogen peroxide in the recent past include [[Air Liquide]] and [[DuPont]]. DuPont recently sold its hydrogen peroxide manufacturing business to Degussa.
Propellant grade hydrogen peroxide is available to qualified buyers. Typically this chemical is only sold to commercial companies or government institutions which have the ability to properly handle and utilize the material. Non-professionals have purchased 70% or lower concentration hydrogen peroxide (the remaining 30% is water with traces of impurities and stabilizing materials, such as tin salts, phosphates, nitrates, and other chemical additives), and increased its concentration themselves. Many amateurs try [[distillation]], but this is extremely dangerous with hydrogen peroxide; peroxide vapor can ignite or detonate depending on specific combinations of temperature and pressure. In general any boiling mass of high concentration hydrogen peroxide at ambient pressure will produce vapor phase hydrogen peroxide which can detonate. This hazard is mitigated, but not entirely eliminated with vacuum distillation. Other approaches for concentrating hydrogen peroxide are [[Sparging (chemistry)|sparging]] and [[Fractional crystallization (chemistry)|fractional crystallization]].
High concentration hydrogen peroxide is readily available in 70, 90, and 98% concentrations in sizes of 1 gallon, 30 gallon, and bulk tanker truck volumes. Propellant grade hydrogen peroxide is being used on current military systems and is in numerous defense and aerospace research and development programs. Many privately funded rocket companies are using hydrogen peroxide, notably [[Blue Origin]], and some amateur groups have expressed interest in manufacturing their own peroxide, for their use and for sale in small quantities to others.
==Hazards==
Hydrogen peroxide, either in pure or diluted form, can pose several risks:
* Above roughly 70% concentrations, hydrogen peroxide can give off vapor that can detonate above 70 °C (158 °F) at normal atmospheric pressure.<ref>{{cite web|title=Hydrogen peroxide|publisher=Chemie.de Information Service|url=http://www.chemie.de/lexikon/e/Hydrogen_peroxide|accessdate=2008-04-04}}</ref> This can then cause a boiling liquid expanding vapor explosion ([[BLEVE]]) of the remaining liquid. [[Distillation]] of hydrogen peroxide at normal pressures is thus highly dangerous.
* Hydrogen peroxide vapors can form sensitive contact explosives with hydrocarbons such as greases. Hazardous reactions ranging from ignition to explosion have been reported with [[alcohol]]s, [[ketone]]s, [[carboxylic acid]]s (particularly [[acetic acid]]), [[amine]]s and [[phosphorus]].{{Fact|date=June 2007}} The saying is "peroxides kill chemists".{{Fact|date=June 2007}}<!--{{DOI|10.1016/S1074-9098(01)00247-7}}-->
* Concentrated hydrogen peroxide, if spilled on clothing (or other flammable materials), will preferentially evaporate water until the concentration reaches sufficient strength, at which point the material may spontaneously ignite. <ref>http://www.ntsb.gov/publictn/2000/HZB0001.htm</ref><ref>[http://media.armadilloaerospace.com/misc/MaterialTest.mpg Armadilloaerospace material tests with HTP]</ref>
* Concentrated hydrogen peroxide (>50%) is corrosive, and even domestic-strength solutions can cause irritation to the eyes, [[mucous membrane]]s and skin.<ref>For example, see an [http://www.jtbaker.com/msds/englishhtml/h4070.htm MSDS for a 3% peroxide solution].</ref> Swallowing hydrogen peroxide solutions is particularly dangerous, as decomposition in the stomach releases large quantities of gas (10 times the volume of a 3% solution) leading to internal bleeding. Inhaling over 10% can cause severe pulmonary irritation.{{Fact|date=June 2007}}
* Low concentrations of hydrogen peroxide, on the order of 3% or less, will chemically bleach many types of clothing to a pinkish hue. Caution should be exercised when using common products that may contain hydrogen peroxide, such as facial cleaner or contact lens solution, which easily splatter upon other surfaces.
* Large oral doses of Hydrogen peroxyde on a 3% concentration may cause "irritation and blistering to the mouth, throat, and abdomen", as well as "abdominal pain, vomiting, and diarrhea". <ref>[http://www.sefsc.noaa.gov/HTMLdocs/HydrogenPeroxide3.htm Hydrogen Peroxide, 3%. 3. Hazards Identification] Southeast Fisheries Science Center, daughter agency of [[NOAA]].</ref>
==Historical Incidents==
* Several people were injured after a hydrogen peroxide spill on board Northwest Airlines flight 957 from Orlando to Memphis on October 28, 1998.<ref>Hazardous Materials Incident Brief DCA-99-MZ-001, [http://www.ntsb.gov/publictn/2000/HZB0001.htm "Spill of undeclared shipment of hazardous materials in cargo compartment of aircraft"]. pub: National Transportation Safety Board. October 28, 1998; adopted May 17, 2000.</ref>
* During the [[Second World War]], Doctors in Nazi concentration camps experimented with the use of hydrogen peroxide injections in the killing of human subjects.<ref>{{cite web | title=The Nazi Doctors: Medical Killing and the Psychology of Genocide | publisher=Robert Jay Lifton | url=http://www.holocaust-history.org/lifton/LiftonT257.shtml | accessmonthday=1 November |accessyear=2007}}</ref>
* Hydrogen peroxide was said to be one of the ingredients in the bombs which failed to explode in the [[21 July 2005 London bombings]].<ref>Four Men Found Guilty in Plot to Blow Up London’s Transit System, [http://www.foxnews.com/story/0,2933,288631,00.html "FOXNews.com"]. (July 9, 2007)</ref>
A [[material safety data sheet]] will contain more information on the risks of working with this chemical.<!-- we should ideally list a few here, for various concentrations perhaps -->
==References==
{{refbegin}}
* J. Drabowicz ''et al.'', in ''The Syntheses of Sulphones, Sulphoxides and Cyclic Sulphides'', p112-116, G. Capozzi ''et al.'', eds., John Wiley & Sons, Chichester, UK, 1994. ISBN 0-471-93970-6.
* N. N. Greenwood, A. Earnshaw, ''Chemistry of the Elements'', 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997. A great description of properties & chemistry of H<sub>2</sub>O<sub>2</sub>.
* J. March, ''Advanced Organic Chemistry'', 4th ed., p. 723, Wiley, New York, 1992.
* W. T. Hess, ''Hydrogen Peroxide'', in ''Kirk-Othmer Encyclopedia of Chemical Technology'', 4th edition, Wiley, New York, Vol. 13, 961-995 (1995).
{{refend}}
{{reflist}}
==External links==
* [http://msds.fmc.com/msds/100000010225-MSDS_US-E.pdf Material Safety Data Sheet]
* [http://www.atsdr.cdc.gov/tfactsx4.html ATSDR Agency for Toxic Substances and Disease Registry FAQ]
* [http://www.erps.org Experimental Rocket Propulsion Society]
* [http://www.compchemwiki.org/index.php?title=Hydrogen_peroxide Computational Chemistry Wiki]
* [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc01/icsc0164.htm International Chemical Safety Card 0164]
* [http://www.cdc.gov/niosh/npg/npgd0335.html NIOSH Pocket Guide to Chemical Hazards]
* [http://www-cie.iarc.fr/htdocs/monographs/vol71/023-hydrogenper.html IARC Monograph "Hydrogen Peroxide"]
* [http://www.gkllc.com General Kinetics Inc. Hydrogen Peroxide Rocket Engines and Gas Generators]
* [http://www.quackwatch.org/01QuackeryRelatedTopics/Cancer/oxygen.html Oxygenation Therapy:Unproven Treatments for Cancer and AIDS]
* [http://www.flywriterproductions.com/sites/themolecule/index.html H2O2 and HYPER OXYGEN THERAPY]
* [http://news.bbc.co.uk/1/hi/england/london/4197500.stm Explosion of a lorry carrying hydrogen peroxide closes M25 motorway.]
* [http://www.gaiaresearch.co.za/hydroperoxide.html Hydrogen Peroxide in the Human Body]
* [http://www.using-hydrogen-peroxide.com Information on many common uses for hydrogen peroxide, especially household uses.]
* [http://copublications.greenfacts.org/en/tooth-whiteners/index.htm Hydrogen peroxide in tooth whiteners] summary by [[GreenFacts]] of the European Commission SCCP assessment
* [http://bilclarke.blogspot.com/2008/05/switch-your-hot-tub-to-hydrogen.html Step-By-Step Instructions For Converting Your Hot-Tub to Hydrogen Peroxide]
{{Stomatological preparations}}
{{Antiseptics and disinfectants}}
{{Otologicals}}
[[Category:Antiseptics]]
[[Category:Bleaches]]
[[Category:Disinfectants]]
[[Category:Household chemicals]]
[[Category:Hydrogen compounds]]
[[Category:Peroxides]]
[[Category:Rocket oxidizers]]
[[Category:1894 introductions]]
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