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Hydrogen peroxideFrom Wikipedia, the free encyclopediaJump to: navigation, search
Hydrogen peroxide
IUPAC name [hide] dihydrogen dioxideOther names[hide]
DioxidaneIdentifiers
CAS number 7722-84-1
PubChem 784ChemSpider 763
UNII BBX060AN9V
EC number 231-765-0
UN number2015 (>60% soln.)2014 (20–60% soln.)2984 (8–20% soln.)
KEGG D00008
ChEMBL CHEMBL71595
IUPHAR ligand 2448
RTECS numberMX0900000 (>90% soln.)MX0887000 (>30% soln.)
SMILES[show]
InChI[show]
PropertiesMolecular formula H2O2
Molar mass 34.0147 g/mol
AppearanceVery light blue color; colorless in solution
Density1.110 g/cm3 (20 °C, 30-percent)1.450 g/cm3 (20 °C, pure)
Melting point-0.43 °C, 273 K, 31 °F
Boiling point150.2 °C, 423 K, 302 °F
Solubility in water MiscibleSolubility soluble in etherAcidity (pKa) 11.62 [1]
Refractive index (nD) 1.34Viscosity 1.245 cP (20 °C)Dipole moment 2.26 D
ThermochemistryStd enthalpy of -4.007 kJ/g
formation ΔfHo298
Specific heat capacity, C
1.267 J/g K (gas)2.619 J/g K (liquid)
HazardsMSDS ICSC 0164 (>60% soln.)EU Index 008-003-00-9
EU classificationOxidant (O)Corrosive (C)Harmful (Xn)
R-phrases R5, R8, R20/22, R35
S-phrases(S1/2), S17, S26, S28, S36/37/39, S45
NFPA 704
032
OXFlash point Non-flammableLD50 1518 mg/kg
Related compounds
Related compounds
WaterOzoneHydrazineHydrogen disulfide
(what is this?) (verify)Except where noted otherwise, data are given for materials in
their standard state (at 25 °C, 100 kPa) Infobox references
Hydrogen peroxide (H2O2) is an oxidizer commonly used as a bleach. It is the simplest peroxide (a compound with an oxygen-oxygen single bond). Hydrogen peroxide is a clear liquid, slightly more viscous than water, that appears colorless in dilute solution. It is used as a disinfectant, antiseptic, oxidizer, and in rocketry as a propellant.[2] The oxidizing capacity of hydrogen peroxide is so strong that it is considered a highly reactive oxygen species.
Hydrogen peroxide is naturally produced in organisms as a by-product of oxidative metabolism. Nearly all living things (specifically, all obligate and facultative aerobes) possess enzymes known as peroxidases, which harmlessly and catalytically decompose low concentrations of hydrogen peroxide to water and oxygen.
Contents
[hide] 1 Structure and properties
o 1.1 Comparison with analogues
o 1.2 Physical properties of hydrogen peroxide solutions o 1.3 pH of H 2O2
2 History 3 Manufacture
o 3.1 New developments o 3.2 Availability
4 Reactions o 4.1 Decomposition o 4.2 Redox reactions o 4.3 Formation of peroxide compounds o 4.4 Alkalinity
5 Uses o 5.1 Industrial applications o 5.2 Chemical applications o 5.3 Biological function o 5.4 Domestic uses o 5.5 Use as propellant o 5.6 Therapeutic use o 5.7 Improvised explosive device / home-made bomb precursor
6 Safety o 6.1 Historical incidents
7 See also 8 References
o 8.1 Notes o 8.2 Bibliography
9 External links
[edit] Structure and properties
H2O2 adopts a nonplanar structure of C2 symmetry. Although chiral, the molecule undergoes rapid racemization. The flat shape of the anti conformer would minimize steric repulsions, the 90° torsion angle of the syn conformer 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.[3] The observed anticlinal "skewed" shape is a compromise between the two conformers.
Despite the fact that the O-O bond is a single bond, the molecule has a high barrier to complete rotation of 29.45 kJ/mol (compared with 12.5 kJ/mol for the rotational barrier of ethane). The increased barrier is attributed to repulsion between one lone pair and other lone pairs. The 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 H2O2.
[edit] Comparison with analogues
Analogues of hydrogen peroxide include the chemically identical deuterium peroxide and hydrogen disulfide.[4] Hydrogen disulfide has a boiling point of only 70.7°C despite having a higher molecular weight, indicating that hydrogen bonding increases the boiling point of hydrogen peroxide.
[edit] Physical properties of hydrogen peroxide solutions
The properties of aqueous solutions of hydrogen peroxide differ from those of the neat material, reflecting the effects of hydrogen bonding between water and hydrogen peroxide molecules. Hydrogen peroxide and water form a eutectic mixture, exhibiting freezing-point depression. Whereas pure water melts and freezes at approximately 273K, and pure hydrogen peroxide just 0.4K below that, a 50% (by volume) solution melts and freezes at 221 K.[5]
[edit] pH of H2O2
Pure hydrogen peroxide has a pH of 6.2, making it a weak acid. The pH can be as low as 4.5 when diluted at approximately 60%.[6]
[edit] History
Hydrogen peroxide was first isolated in 1818 by Louis Jacques Thénard by reacting barium peroxide with nitric acid.[7] 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.[8] Modern production methods are discussed below.
For a long time, pure hydrogen peroxide was believed to be unstable, because attempts to separate the hydrogen peroxide from the water, which is present during synthesis, failed. This instability was however due to traces of impurities (transition metals salts) that catalyze the decomposition of the hydrogen peroxide. One hundred percent pure hydrogen peroxide was first obtained through vacuum distillation by Richard Wolffenstein in 1894.[9] At the end of 19th century, Petre Melikishvili and his pupil L. Pizarjevski showed that of the many proposed formulas of hydrogen peroxide, the correct one was H-O-O-H.
The use of H2O2 sterilization in biological safety cabinets and barrier isolators is a popular alternative to ethylene oxide (EtO) as a safer, more efficient decontamination method. H2O2 has long been widely used in the pharmaceutical industry. In aerospace research, H2O2 is used to sterilize artificial satellites and space probes.
The U.S. FDA has recently granted 510(k) clearance to use H2O2 in individual medical device manufacturing applications. EtO criteria outlined in ANSI/AAMI/ISO 14937 may
be used as a validation guideline. Sanyo was the first manufacturer to use the H2O2 process in situ in a cell culture incubator, which is a faster and more efficient cell culture sterilization process[citation needed].
[edit] Manufacture
Formerly, hydrogen peroxide was prepared by the electrolysis of an aqueous solution of sulfuric acid or acidic ammonium bisulfate (NH4HSO4), followed by hydrolysis of the peroxodisulfate ((SO4)2)2− that is formed. Today, hydrogen peroxide is manufactured almost exclusively by the autoxidation of a 2-alkyl anthrahydroquinone (or 2-alkyl-9,10-dihydroxyanthracene) to the corresponding 2-alkyl anthraquinone in the so called anthraquinone process. Major producers commonly use either the 2-ethyl or the 2-amyl derivative. The cyclic reaction depicted below shows the 2-ethyl derivative, where 2-ethyl-9,10-dihydroxyanthracene (C16H14O2) is oxidized to the corresponding 2-ethylanthraquinone (C16H12O2) and hydrogen peroxide. Most commercial processes achieve this by bubbling compressed air through a solution of the anthracene, whereby the oxygen present in the air reacts with the labile hydrogen atoms (of the hydroxy group), giving hydrogen peroxide and regenerating the anthraquinone. Hydrogen peroxide is then extracted and the anthraquinone derivative is reduced back to the dihydroxy (anthracene) compound using hydrogen gas in the presence of a metal catalyst. The cycle then repeats itself.[10][11]
This process is known as the Riedl-Pfleiderer process,[11] having been first discovered by them in 1936. The overall equation for the process is deceptively simple:[10]
H2 + O2 → H2O2
The economics of the process depend heavily on effective recycling of the quinone (which is expensive) and extraction solvents, and of the hydrogenation catalyst.
In 1994, world production of H2O2 was around 1.9 million tonnes and grew to 2.2 million in 2006,[12] most of which was at a concentration of 70% or less[citation needed]. In that year bulk 30% H2O2 sold for around US $0.54 per kg, equivalent to US $1.50 per kg (US $0.68 per lb) on a "100% basis[citation needed]".
[edit] New developments
A new, so-called "high-productivity/high-yield" process, based on an optimized distribution of isomers of 2-amyl anthraquinone, has been developed by Solvay. In July 2008, this process allowed the construction of a "mega-scale" single-train plant in Zandvliet (Belgium). The plant has an annual production capacity more than twice that of the world's next-largest single-train plant. An even-larger plant is scheduled to come onstream at Map Ta Phut (Thailand) in 2011. It is likely that this will lead to a reduction in the cost of production due to economies of scale.[13]
A process to produce hydrogen peroxide directly from the elements has been of interest for many years. The problem with the direct synthesis process is that, in terms of thermodynamics, the reaction of hydrogen with oxygen favors production of water. It had been recognized for some time that a finely dispersed catalyst is beneficial in promoting selectivity to hydrogen peroxide, but, while selectivity was improved, it was still not sufficiently high to permit commercial development of the process. However, an apparent breakthrough was made in the early 2000s by researchers at Headwaters Technology. The breakthrough revolves around development of a minute (nanometer-size) phase-controlled noble metal crystal particles on carbon support. This advance led, in a joint venture with Evonik Industries, to the construction of a pilot plant in Germany in late 2005. It is claimed that there are reductions in investment cost because the process is simpler and involves less equipment; however, the process is also more corrosive and unproven. This process results in low concentrations of hydrogen peroxide (about 5–10 wt% versus about 40 wt% through the anthraquione process).[13]
In 2009, another catalyst development was announced by workers at Cardiff University.[14] This development also relates to the direct synthesis, but, in this case, using gold–palladium nanoparticles. Under normal circumstances, the direct synthesis must be carried out in an acid medium to prevent immediate decomposition of the hydrogen peroxide once it is formed. Whereas hydrogen peroxide tends to decompose on its own (which is why, even after production, it is often necessary to add stabilisers to the commercial product when it is to be transported or stored for long periods), the nature of the catalyst can cause this decomposition to accelerate rapidly. It is claimed that the use of this gold-palladium catalyst reduces this decomposition and, as a consequence, little to no acid is required. The process is in a very early stage of development and currently results in very low concentrations of hydrogen peroxide being formed (less than about 1–2 wt%). Nonetheless, it is envisaged by the inventors that the process will lead to an inexpensive, efficient, and environmentally friendly process.[13][14][15][16]
A novel electrochemical process for the production of alkaline hydrogen peroxide has been developed by Dow. The process employs a monopolar cell to achieve an electrolytic reduction of oxygen in a dilute sodium hydroxide solution.[13]
[edit] Availability
Hydrogen peroxide is most commonly available as a solution in water. For consumers, it is usually available from pharmacies at 3 and 6 wt% concentrations. The concentrations are sometimes described in terms of the volume of oxygen gas generated (see decomposition); one milliliter of a 20-volume solution generates twenty milliliters of oxygen gas when completely decomposed. For laboratory use, 30 wt% solutions are most common. Commercial grades from 70% to 98% are also available, but due to the potential of solutions of >68% hydrogen peroxide to be converted entirely to steam and oxygen (with the temperature of the steam increasing as the concentration increases above 68%) these grades are potentially far more hazardous, and require special care in dedicated storage areas. Buyers must typically submit to inspection by the small number of commercial manufacturers.
[edit] Reactions
[edit] Decomposition
Manganese dioxide decomposing a very dilute solution of hydrogen peroxide
Hydrogen peroxide decomposes (disproportionates) exothermically into water and oxygen gas spontaneously:
2 H2O2 → 2 H2O + O2
This process is thermodynamically favorable. It has a Δ H o of −98.2 kJ·mol−1 and a Δ G o of −119.2 kJ·mol−1 and a ΔS of 70.5 J·mol−1·K−1. 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 metals and their compounds. Common catalysts include manganese dioxide, silver, and platinum.[17] 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 test peroxide, or HTP (also called high-strength peroxide) must be stored in a suitable,[citation needed] 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 Fe2+ or Ti3+, the decomposition may take a different path, with free radicals such as HO· (hydroxyl) and HOO· being formed. A combination of H2O2 and Fe2+ 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 1.667 mol/dm3 (Molar solution) or about 6%.
[edit] Redox reactions
This section does not cite any references or sources.Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (July 2010)
In acidic solutions, H2O2 is one of the most powerful oxidizers known—stronger than chlorine, chlorine dioxide, and potassium permanganate. Also, through catalysis, H2O2 can be converted into hydroxyl radicals (.OH), which are highly reactive.
Oxidant/Reduced product Oxidation potential, VFluorine/Hydrogen fluoride 3.0Ozone/Oxygen 2.1Hydrogen peroxide/Water 1.8Potassium permanganate/Manganese dioxide 1.7Chlorine dioxide/HClO 1.5Chlorine/Chloride 1.4
In aqueous solutions, hydrogen peroxide can oxidize or reduce a variety of inorganic ions. When it acts as a reducing agent, oxygen gas is also produced.
In acidic solutions Fe2+ is oxidized to Fe3+ (hydrogen peroxide acting as an oxidizing agent),
2 Fe2+(aq) + H2O2 + 2 H + (aq) → 2 Fe3+(aq) + 2H2O(l)
and sulfite (SO32−) is oxidized to sulfate (SO4
2−). However, potassium permanganate is reduced to Mn2+ by acidic H2O2. Under alkaline conditions, however, some of these reactions reverse; for example, Mn2+ is oxidized to Mn4+ (as MnO2).
Other examples of hydrogen peroxide's action as a reducing agent are reaction with sodium hypochlorite or potassium permanganate, which is a convenient method for preparing oxygen in the laboratory.
NaOCl + H2O2 → O2 + NaCl + H2O 2 KMnO4 + 3 H2O2 → 2 MnO2 + 2 KOH + 2 H2O + 3 O2
Hydrogen peroxide is frequently used as an oxidizing agent in organic chemistry. One application is for the oxidation of thioethers to sulfoxides.[citation needed] For example, methyl phenyl sulfide was oxidized to methyl phenyl sulfoxide in 99% yield in methanol in 18 hours (or 20 minutes using a TiCl3 catalyst):[citation needed]
Ph-S-CH3 + H2O2 → Ph-S(O)-CH3 + H2O
Alkaline hydrogen peroxide is used for epoxidation of electron-deficient alkenes such as acrylic acids, and also for oxidation of alkylboranes to alcohols, the second step of hydroboration-oxidation.
[edit] Formation of peroxide compounds
Hydrogen peroxide is a weak acid, and it can form hydroperoxide or peroxide salts or derivatives of many metals.
For example, on addition to an aqueous solution of chromic acid (CrO3) or acidic solutions of dichromate salts, it will form an unstable blue peroxide CrO(O2)2. In aqueous solution it rapidly decomposes to form oxygen gas and chromium salts.
It can also produce peroxoanions by reaction with anions; for example, reaction with borax leads to sodium perborate, a bleach used in laundry detergents:
Na2B4O7 + 4 H2O2 + 2 NaOH → 2 Na2B2O4(OH)4 + H2O
H2O2 converts carboxylic acids (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 H2O2 in some reactions.
[edit] Alkalinity
Hydrogen peroxide can still form adducts with very strong acids. The superacid HF/SbF5 forms unstable compounds containing the [H3O2]+ ion.
[edit] Uses
[edit] Industrial applications
ISO tank container for hydrogen peroxide transportation.
About 50% of the world's production of hydrogen peroxide in 1994 was used for pulp- and paper-bleaching.[12] Other bleaching applications are becoming more important as hydrogen peroxide is seen as an environmentally benign alternative to chlorine-based bleaches.
Other major industrial applications for hydrogen peroxide include the manufacture of sodium percarbonate and sodium perborate, used as mild bleaches in laundry detergents. It is used in the production of certain organic peroxides such as dibenzoyl peroxide, used in polymerisations and other chemical processes. Hydrogen peroxide is also used in the production of epoxides such as propylene oxide. Reaction with carboxylic acids 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 alkenes 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 CO2 and high-temperature steam for a variety of purposes.[18]
Recently, there has been increased use of vaporized hydrogen peroxide in the validation and bio-decontamination of half-suit and glove-port isolators in pharmaceutical production.
Nuclear pressurized water reactors (PWRs) use hydrogen peroxide during the plant shutdown to force the oxidation and dissolution of activated corrosion products deposited on the fuel. The corrosion products are then removed with the cleanup systems before the reactor is disassembled.
Hydrogen peroxide is also used in the oil and gas exploration industry to oxidize rock matrix in preparation for micro-fossil analysis.
[edit] Chemical applications
A method of producing propylene oxide from hydrogen peroxide has been developed. The process is claimed to be environmentally friendly, since the only significant byproduct is water. It is also claimed the process has significantly lower investment and operating costs. Two of these "HPPO" (hydrogen peroxide to propylene oxide) plants came onstream in 2008: One of them located in Belgium is a Solvay, Dow-BASF joint venture, and the other in Korea is a EvonikHeadwaters, SK Chemicals joint venture. A caprolactam application for hydrogen peroxide has been commercialized. Potential routes to phenol and epichlorohydrin utilizing hydrogen peroxide have been postulated.[13]
[edit] Biological function
Hydrogen peroxide is also one of the two chief chemicals in the defense system of the bombardier beetle, reacting with hydroquinone to discourage predators.
A study published in Nature found that hydrogen peroxide plays a role in the immune system. Scientists found that hydrogen peroxide is released after tissues are damaged in zebra fish, which is thought to act as a signal to white blood cells to converge on the site and initiate the healing process. When the genes required to produce hydrogen peroxide were disabled, white blood cells did not accumulate at the site of damage. The experiments were conducted on fish; however, because fish are genetically similar to humans, the same process is speculated to occur in humans. The study in Nature suggested asthma sufferers have higher levels of hydrogen peroxide in their lungs than healthy people, which could explain why asthma sufferers have inappropriate levels of white blood cells in their lungs.[19][20]
Skin immediately after exposure to 30% H2O2
Diluted H2O2 (between 3% and 8%) is used to bleach human hair when mixed with ammonium hydroxide, hence the phrase "peroxide blonde".
It is absorbed by skin upon contact and creates a local skin capillary embolism that appears as a temporary whitening of the skin.
It is used to whiten bones that are to be put on display. 3% H2O2 is used medically for cleaning wounds, removing dead tissue, and as an
oral debriding agent. Peroxide stops slow (small vessel) wound bleeding/oozing, as well. However, recent studies have suggested that hydrogen peroxide impedes scarless healing as it destroys newly formed skin cells.[21] Most over-the-counter peroxide solutions are not suitable for ingestion.
If a dog has swallowed a harmful substance (e.g., rat poison), small amounts of hydrogen peroxide can be given to induce vomiting.[22]
35% hydrogen peroxide is used to prevent infection transmission in the hospital environment, hydrogen peroxide vapor is registered with the US EPA as a sporicidal sterilant.
3% H2O2 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 horticulturalists and users of hydroponics advocate the use of weak hydrogen peroxide solution in watering solutions. 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) and a variety of other pests.[23][24] There is some peer-reviewed academic research to back up some of the claims.[25]
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.[26][27] 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 Biochemical Oxygen Demand (BOD).
Mixed with baking soda and a small amount of hand soap, hydrogen peroxide is effective at removing skunk odor.[28]
Hydrogen peroxide is used with phenyl oxalate ester and an appropriate dye in glow sticks as an oxidizing agent. It reacts with the ester to form an unstable CO2 dimer, which excites the dye to an excited state; the dye emits a photon (light) when it spontaneously relaxes back to the ground state.
Hydrogen peroxide can be combined with vinegar and table salt to form a substitute for industrial chemicals such as ferric chloride, ammonium persulfate, or hydrochloric acid as a hobbyist's printed circuit board etchant.[29]
[edit] Use as propellant
For more details on this topic, see High test peroxide.
Rocket Belt hydrogen peroxide propulsion system (see Jet packs)
High concentration H2O2 is referred to as HTP or High test peroxide. It 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. H2O2 monopropellant produces a maximum specific impulse (Isp) of 161 s (1.6 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 H2O2 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 Isp than liquid oxygen, but is dense, storable, noncryogenic and can be more easily used to drive gas turbines to give high pressures using an efficient closed cycle. 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, containing oxyquinoline stabilizer, for the Me-163), and for the low-cost British Black Knight and Black Arrow launchers.
In the 1940s and 1950s, the Walter turbine used hydrogen peroxide for use in submarines while submerged; it was found to be too noisy and require too much maintenance compared to diesel-electric power systems. Some torpedoes used hydrogen peroxide as oxidizer or propellant, but this was dangerous and has been discontinued by most navies. Hydrogen peroxide leaks were blamed for the sinkings of HMS Sidon and the Russian submarine Kursk . It was discovered, for example, by the Japanese Navy in torpedo trials, that the concentration of H2O2 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.[30]
While rarely used now as a monopropellant for large engines, small hydrogen peroxide attitude control thrusters are still in use on some satellites. 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.
[edit] Therapeutic use
Hydrogen peroxide is generally recognized as safe (GRAS) as an antimicrobial agent, an oxidizing agent and for other purposes by the FDA.[31]
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 readily available over the counter products, it is still used by many hospitals, doctors and dentists.
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.[32]
Hydrogen peroxide and benzoyl peroxide are sometimes used to treat acne.[33] Hydrogen peroxide is used as an emetic in veterinary practice.[34]
Alternative uses 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." [35]
Another controversial alternative medical procedure is inhalation of hydrogen peroxide at a concentration of about 1%. Intravenous usage of hydrogen peroxide has been linked to several deaths.[36][37]
See also Liquid Oxygen (supplement)
[edit] Improvised explosive device / home-made bomb precursor
Hydrogen peroxide was the main ingredient in the 7 July 2005 London bombings that killed 52 London Underground and bus passengers. The bomb-making ingredients are reported to be easier to buy than large numbers of aspirin pills.[38]
[edit] Safety
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 H2O2 will react violently.
High-concentration hydrogen peroxide streams, typically above 40%, should be considered a D001 hazardous waste, due to concentrated hydrogen peroxide's meeting the definition of a DOT oxidizer according to U.S. regulations, if released into the environment. The EPA Reportable Quantity (RQ) for D001 hazardous wastes is 100 pounds, or approximately ten gallons, of concentrated hydrogen peroxide.
Hydrogen peroxide should be stored in a cool, dry, well-ventilated area and away from any flammable or combustible substances.[39] 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).[40] 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.[41]
Hydrogen peroxide, either in pure or diluted form, can pose several risks:
Explosive vapors. Above roughly 70% concentrations, hydrogen peroxide can give off vapor that can detonate above 70 °C (158 °F) at normal atmospheric pressure.[citation needed] 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.
Hazardous reactions. Hydrogen peroxide vapors can form sensitive contact explosives with hydrocarbons such as greases. Hazardous reactions ranging from ignition to explosion have been reported with alcohols, ketones, carboxylic acids (particularly acetic acid), amines and phosphorus.[citation needed]
Spontaneous ignition. 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.[42][43]
Corrosive. Concentrated hydrogen peroxide (>50%) is corrosive, and even domestic-strength solutions can cause irritation to the eyes, mucous membranes and skin.[44] 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.[citation needed]
Bleach agent. 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.
Internal ailments. Large oral doses of hydrogen peroxide at a 3% concentration may cause "irritation and blistering to the mouth, (which is known as Black hairy tongue) throat, and abdomen", as well as "abdominal pain, vomiting, and diarrhea".[45]
Vapor pressure. Hydrogen peroxide has a significant vapor pressure (1.2 kPa at 50 oC[CRC Handbook of Chemistry and Physics, 76th Ed, 1995-1996]) and exposure to the vapor is potentially hazardous. Hydrogen peroxide vapor is a primary irritant, primarily affecting the eyes and respiratory system and the NIOSH Immediately dangerous to life and health limit (IDLH) is only 75 ppm. Documentation for Immediately Dangerous to Life or Health Concentrations (IDLH): NIOSH [http://www.cdc.gov/NIOSH/National Institute for Occupational Safety and Health] Chemical Listing and Documentation of Revised IDLH Values (as of 3/1/95). Long term exposure to low ppm concentrations is also hazardous and can result in permanent lung damage and OSHA Occupational Safety and Health Administration has established a permissible exposure limit of 1.0 ppm calculated as an eight hour time weighted average (29 CFR 1910.1000, Table Z-1) and hydrogen peroxide has also been classified by the ACGIH American Conference of Industrial Hygienists (ACGIH) as a "known animal carcinogen, with unknown relevance on humans.[2008 Threshold Limit Values for Chemical Substances and Physical Agents & Biological Exposure Indices, ACGIH] In applications where high concentrations of hydrogen peroxide are used, suitable personal protective equipment should be worn and it is prudent in situations where the vapor is likely to be generated, such as hydrogen peroxide gas or vapor sterilization, to ensure that there is adequate ventilation and the vapor concentration monitored with a continuous gas monitor for hydrogen peroxide. Continuous gas monitors for hydrogen peroxide are available from several suppliers. Further information on the hazards of hydrogen peroxide is available from OSHA Occupational Safety and Health Guideline for Hydrogen Peroxide and from the ATSDR. Agency for Toxic Substances and Disease Registry
Skin disorders. Vitiligo is an acquired skin disorder with the loss of native skin pigment, which affects about 0.5-1% of the world population. Recent studies have discovered increased H2O2 levels in the epidermis and in blood are one of many hallmarks of this disease.[46]
[edit] Historical incidents
On July 16, 1934 in Kummersdorf, Germany a rocket engine using hydrogen peroxide exploded, killing three people. As a result of this incident, Werner von Braun decided not to use hydrogen peroxide as an oxidizer in the rockets he developed afterward.
Several people received minor injuries after a hydrogen peroxide spill on board Northwest Airlines flight 957 from Orlando to Memphis on October 28, 1998 and subsequent fire on Northwest Airlines flight 7.[47]
During the Second World War, doctors in Nazi concentration camps experimented with the use of hydrogen peroxide injections in the killing of human subjects.[48]
Hydrogen peroxide was said to be one of the ingredients in the bombs that failed to explode in the July 21, 2005 London bombings.[49]
The Russian submarine K-141 Kursk sailed out to sea to perform an exercise of firing dummy torpedoes at the Pyotr Velikiy, a Kirov class battlecruiser. On August 12, 2000 at 11:28 local time (07:28 UTC), there was an explosion while preparing to fire the torpedoes. The only credible report to date is that this was due to the failure and explosion of one of the Kursk's hydrogen peroxide-fueled torpedoes. It is believed that HTP, a form of highly concentrated hydrogen peroxide used as propellant for the torpedo, seeped through rust in the torpedo casing. A similar incident was responsible for the loss of HMS Sidon in 1955
On August 16, 2010 a spill of about 10 gallons of cleaning fluid spilled on the 53rd floor of 1515 Broadway, in Times Square, New York City. The spill, which a spokesperson for the New York City fire department said was of Hydrogen Peroxide, shut down Broadway between West 42nd and West 48th streets as a number of fire engines responded to the hazmat situation. There were no reported injuries.[50]
[edit] See also
Elephant toothpaste
[edit] References
[edit] Notes
1. ̂ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
2. ̂ Hill, C. N. (2001). A Vertical Empire: The History of the UK Rocket and Space Programme, 1950-1971. Imperial College Press. ISBN 9781860942686. http://books.google.com/?id=AzoCJfTmRDsC.
3. ̂ Dougherty, Dennis A.; Eric V. Anslyn (2005). Modern Physical Organic Chemistry. University Science. p. 122. ISBN 1-891389-31-9.
4. ̂ Landolt-Börnstein Substance – Property Index 5. ̂ 60% hydrogen peroxide msds 50% H2O2 MSDS
6. ̂ What is the pH of H2O2 solutions? | H2O2.com – US Peroxide – Technologies for Clean Environment
7. ̂ L. J. Thénard (1818). "Observations sur des nouvelles combinaisons entre l’oxigène et divers acides". Annales de chimie et de physique, 2nd series 8: 306–312. http://books.google.com/books?id=-N43AAAAMAAJ&pg=PA306#v=onepage&q&f=false.
8. ̂ C. W. Jones, J. H. Clark. Applications of Hydrogen Peroxide and Derivatives. Royal Society of Chemistry, 1999.
9. ̂ Richard Wolffenstein (1894). "Concentration und Destillation von Wasserstoffsuperoxyd". Berichte der deutschen chemischen Gesellschaft 27 (3): 3307–3312. doi:10.1002/cber.189402703127.
10. ^ a b Jose M. Campos-Martin, Gema Blanco-Brieva, Jose L. G. Fierro (2006). "Hydrogen Peroxide Synthesis: An Outlook beyond the Anthraquinone Process". Angewandte Chemie International Edition 45 (42): 6962–6984. doi:10.1002/anie.200503779. PMID 17039551.
11. ^ a b H. Riedl and G. Pfleiderer, U.S. Patent 2,158,525 (October 2, 1936 in USA, and October 10, 1935 in Germany) to I. G. Farbenindustrie, Germany
12. ^ a b Ronald Hage, Achim Lienke (2005). "Applications of Transition-Metal Catalysts to Textile and Wood-Pulp Bleaching". Angewandte Chemie International Edition 45 (2): 206–222. doi:10.1002/anie.200500525. PMID 16342123.
13. ^ a b c d e Hydrogen Peroxide 07/08-03 Report, ChemSystems, May 2009. 14. ^ a b G.J. Hutchings et al, Science, 2009, 323, 1037 15. ̂ "Gold-palladium Nanoparticles Achieve Greener, Smarter Production Of
Hydrogen Peroxide". Sciencedaily.com. 2009-03-03. http://www.sciencedaily.com/releases/2009/02/090219141507.htm. Retrieved 2010-09-05.
16. ̂ Jennifer K. Edwards, Benjamin Solsona, Edwin Ntainjua N, Albert F. Carley (Feb 2009). "Switching off hydrogen peroxide hydrogenation in the direct synthesis process.". Science 323 (5917): 1037–41. doi:10.1126/science.1168980. PMID 19229032.
17. ̂ Petrucci, Ralph H. (2007). General Chemistry: Principles & Modern Applications (9th ed.). Prentice Hall. pp. 606. ISBN 0131493302.
18. ̂ Instant steam puts heat on MRSA, Society Of Chemical Industry 19. ̂ "Natural bleach 'key to healing'". BBC News. 6 June 2009.
http://news.bbc.co.uk/1/hi/health/8078525.stm. Retrieved 2009-07-02. 20. ̂ Niethammer, Philipp; Clemens Grabher, A. Thomas Look & Timothy J.
Mitchison (3 June 2009). "A tissue-scale gradient of hydrogen peroxide mediates rapid wound detection in zebrafish". Nature 459 (7249): 996–999. doi:10.1038/nature08119. ISSN doi=10.1038/nature08119. PMC 2803098. PMID 19494811. http://www.nature.com/nature/journal/v459/n7249/full/nature08119.html. Retrieved 2009-07-02.
21. ̂ "Hydrogen peroxide disrupts scarless fetal wound repair". Cat.inist.fr. http://cat.inist.fr/?aModele=afficheN&cpsidt=17151171. Retrieved 2010-09-05.
22. ̂ How to Induce Vomiting (Emesis) in Dogs 23. ̂ Fredrickson, Bryce. "Hydrogen Peroxide and Horticulture".
http://www.socalplumeriacare.com/Faqs/F-7.pdf. Retrieved 2009-01-25. 24. ̂ Ways to use hydrogen peroxide in the garden 25. ̂ Oxygation Unlocks Yield Potentials of Crops in Oxygen-Limited Soil
Environments Advances in Agronomy, Volume 88, 2005, Pages 313-377 Surya P. Bhattarai, Ninghu Su, David J. Midmore
26. ̂ Great-lakes.org 27. ̂ fws.gov
28. ̂ Chemist Paul Krebaum claims to have originated the formula for use on skunked pets at Skunk Remedy
29. ̂ PCB Etchant from household materials 30. ̂ Scott, Richard (November, 1997). "Homing Instincts". 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 for that purpose to-day. International. http://babriet.tripod.com/articles/art_hominginstinct.htm.
31. ̂ "Sec. 184.1366 Hydrogen peroxide". U.S. Government Printing Office via GPO Access. 2001-04-01. http://a257.g.akamaitech.net/7/257/2422/04nov20031500/edocket.access.gpo.gov/cfr_2001/aprqtr/21cfr184.1366.htm. Retrieved 2007-07-07.
32. ̂ Shepherd, Steven. "Brushing Up on Gum Disease". FDA Consumer. Archived from the original on May 14, 2007. http://web.archive.org/web/20070514102017/http://www.fda.gov/bbs/topics/CONSUMER/CON00065.html. Retrieved 2007-07-07.
33. ̂ Milani, Massimo; Bigardi, Andrea; Zavattarelli, Marco (2003). "Efficacy and safety of stabilised hydrogen peroxide cream (Crystacide) in mild-to-moderate acne vulgaris: a randomised, controlled trial versus benzoyl peroxide gel". Current Medical Research and Opinion 19 (2): 135–138(4). doi:10.1185/030079902125001523. PMID 12740158. http://www.medscape.com/viewarticle/452990.[dead link]
34. ̂ "Drugs to Control or Stimulate Vomiting". Merck Veterinary manual. Merck & Co., Inc. 2006. http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/190303.htm.
35. ̂ "Questionable methods of cancer management: hydrogen peroxide and other 'hyperoxygenation' therapies". CA: a cancer journal for clinicians 43 (1): 47–56. 1993. doi:10.3322/canjclin.43.1.47. PMID 8422605.
36. ̂ Cooper, Anderson (2005-01-12). "A Prescription for Death?". CBS News. http://www.cbsnews.com/stories/2005/01/12/60II/main666489.shtml. Retrieved 2007-07-07.
37. ̂ Mikkelson, Barbara (2006-04-30). "Hydrogen Peroxide". Snopes.com. http://www.snopes.com/medical/healthyself/peroxide.asp. Retrieved 2007-07-07.
38. ̂ BBC News - 7/7 inquests: Coroner warns over bomb ingredient 39. ̂ Hydrogen Peroxide MSDS 40. ̂ Ozonelab Peroxide compatibility 41. ̂ "The Many Uses of Hydrogen Peroxide-Truth! Fiction! Unproven!".
http://www.truthorfiction.com/rumors/h/hydrogen-peroxide.htm. Retrieved 2008-06-30. 42. ̂ NTSB – Hazardous Materials Incident Brief 43. ̂ Armadilloaerospace material tests with HTP 44. ̂ For example, see an MSDS for a 3% peroxide solution. 45. ̂ Hydrogen Peroxide, 3%. 3. Hazards Identification Southeast Fisheries Science
Center, daughter agency of NOAA. 46. ̂ "forschung". Vitiligo.eu.com. http://www.vitiligo.eu.com/turmeric.htm.
Retrieved 2010-09-05. 47. ̂ Hazardous Materials Incident Brief DCA-99-MZ-001, "Spill of undeclared
shipment of hazardous materials in cargo compartment of aircraft". pub: National Transportation Safety Board. October 28, 1998; adopted May 17, 2000.
48. ̂ "The Nazi Doctors: Medical Killing and the Psychology of Genocide". Robert Jay Lifton. http://www.holocaust-history.org/lifton/LiftonT257.shtml. Retrieved 1 November 2007.
49. ̂ Four Men Found Guilty in Plot to Blow Up London's Transit System, "FOXNews.com". (July 9, 2007)
50. ̂ Times Sq. cleaning fluid spill brings fire trucks, [1]. (August 17, 2010)
[edit] Bibliography
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 H2O2.
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).
[edit] External links
This article's use of external links may not follow Wikipedia's policies or guidelines. Please improve this article by removing excessive and inappropriate external links. (June 2010)
Hydrogen Peroxide Distillation for rocket fuel Material Safety Data Sheet ATSDR Agency for Toxic Substances and Disease Registry FAQ Negative effects of Hydrogen Peroxide as an oral rinse Food Grade Hydrogen Peroxide Information Experimental Rocket Propulsion Society International Chemical Safety Card 0164 NIOSH Pocket Guide to Chemical Hazards IARC Monograph "Hydrogen Peroxide" General Kinetics Inc. Hydrogen Peroxide Rocket Engines and Gas Generators Oxygenation Therapy:Unproven Treatments for Cancer and AIDS Hydrogen Peroxide in the Human Body Information on many common uses for hydrogen peroxide, especially household
Sodium hydroxideFrom Wikipedia, the free encyclopedia
Sodium hydroxide
IUPAC name [hide]
Sodium hydroxide
Systematic name [hide]
Sodium oxidanide
Other names[hide]
Caustic soda
Lye
Identifiers
CAS number 1310-73-2
PubChem 14798
ChemSpider 14114
UNII 55X04QC32I
EC number 215-185-5
UN number 1823
KEGG C12569
MeSH Sodium+hydroxide
ChEBI CHEBI:32145
RTECS number WB4900000
Gmelin Reference 68430
SMILES
[show]
InChI
[show]
Properties
Molecular formula NaOH
Exact mass 39.992509329 g mol−1
Appearance White opaque crystals
Density 2.13 g cm−3
Melting point 318 °C, 591 K, 604 °F
Boiling point1388 °C, 1661 K, 2530 °F
Solubility in water 1110 g dm−3 (at 20 °C)
Solubility in methanol 238 g dm−3
Solubility in ethanol <<139 g dm−3
Vapor pressure <18 mmHg (at 20 °C)
Acidity (pKa) 13
Refractive index (nD) 1.412
Hazards
MSDS External MSDS
EU Index 011-002-00-6
EU classification
C
R-phrases R35
S-phrases (S1/2), S26, S37/39, S45
NFPA 704
031
COR
Related compounds
Other anions Sodium hydrosulfide
Other cations Caesium hydroxide
Lithium hydroxide
Potassium hydroxide
Rubidium hydroxide
(what is this?) (verify)
Except where noted otherwise, data are given for materials in their standard
state (at 25 °C, 100 kPa)
Infobox references
Sodium hydroxide (Na OH ), also known as lye and caustic soda, is
a caustic metallic base. It is used in many industries, mostly as a
strong chemical base in the manufacture of pulp andpaper, textiles, drinking
water, soaps and detergents and as a drain cleaner. Worldwide production in 2004
was approximately 60 million tonnes, while demand was 51 million tonnes.[1]
Pure sodium hydroxide is a white solid available in pellets, flakes, granules, and as a
50% saturated solution. It is hygroscopic and readily absorbs water from the air, so it
should be stored in an airtight container. It is very soluble in water with liberation of
heat. It also dissolves in ethanol and methanol, though it exhibits lower solubility in
these solvents than doespotassium hydroxide. Molten sodium hydroxide is also a
strong base, but the high temperature required limits applications. It is insoluble
in ether and other non-polar solvents. A sodium hydroxide solution will leave a yellow
stain on fabric and paper.
Contents
[hide]
1 Properties
2 Reactions
3 Production
o 3.1 Chloralkali electrolysis
4 Uses
o 4.1 pH regulation
o 4.2 Paper making
o 4.3 Tissue digestion
o 4.4 Dissolving amphoteric metals and compounds
o 4.5 Esterification and transesterification reagent
o 4.6 Cleaning agent
o 4.7 Food preparation
o 4.8 Domestic uses
5 Safety
6 See also
7 References
8 Bibliography
9 External links
[edit]Properties
Sodium hydroxide is predominantly ionic, containing
sodium cations and hydroxide anions. The hydroxide anion makes sodium hydroxide
a strong base which reacts with acids to form waterand the corresponding salts.
ΔH°dissolution for aqueous dilution is −44.45 kJ / mol; from aqueous solutions at 12.3–
61.8 °C, it crystallizes in monohydrate, with a melting point 65.1 °C and density of
1.829 g/cm3. The standard enthalpy change of formation (ΔH°form) is −734.95 kJ /
mol.
[edit]Reactions
With acids
Sodium hydroxide reacts with protic acids to give water and the corresponding salts.
For example, with hydrochloric acid, sodium chloride is formed:
NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
In general such neutralization reactions are represented by one simple net ionic
equation:
OH − (aq) + H + (aq) → H2O(l)
This type of reaction with a strong acid releases heat, and hence is referred
to as exothermic. Such acid-base reactions can also be used for titrations.
However, sodium hydroxide is not used as a primary standard because it is
hygroscopic and absorbs carbon dioxide from air.
Sodium hydroxide reacts readily with carboxylic acids to form their salts
and is even a strong enough base to form salts with phenols. It is not,
however, strong enough the quantitatively produce enolates from carbonyl
compounds or deprotonate amines; this would require asuperbase.
With acidic oxides
Sodium hydroxide also reacts with acidic oxides, such as sulfur dioxide.
Such reactions are often used to "scrub" harmful acidic gases (like SO2 and
H2S) produced in the burning of coal and thus prevent their release into the
atmosphere. For example,
2 NaOH + CO2 → Na2CO3 + H2O
With amphoteric metals and oxides
Sodium hydroxide slowly reacts with glass to form sodium silicate, so
glass joints andstopcocks exposed to NaOH have a tendency to
"freeze". Flasks and glass-lined chemical reactors are damaged by
long exposure to hot sodium hydroxide, and the glass becomes
frosted. Sodium hydroxide does not attack iron since iron does not
have amphoteric properties (i.e., it only dissolves in acid, not base). A
few transition metals, however, may react vigorously with sodium
hydroxide.
In 1986, an aluminium road tanker in the UK was mistakenly used to
transport 25% sodium hydroxide solution[citation needed], causing
pressurization of the contents and damage to the tanker. The
pressurization was due to the hydrogen gas which is produced in the
reaction between sodium hydroxide and aluminium:
2 Al + 2 NaOH + 2 H2O → 2 NaAlO2 + 3 H2
Precipitant
Unlike NaOH, the hydroxides of most transition metals are
insoluble, and therefore sodium hydroxide can be used to
precipitate transition metal hydroxides.
Aluminium hydroxide is used as a gelatinous flocculant to filter out
particulate matter in water treatment. Aluminium hydroxide is
prepared at the treatment plant from aluminium sulfate by
reacting it with NaOH.
Al2(SO4)3 + 6 NaOH → 2 Al(OH)3 + 3 Na2SO4
Saponification
NaOH can be used for the base-
driven hydrolysis of esters (as
in saponification), amides and alkyl halides. However, the
limited solubility of NaOH in organic solvents means that the
more soluble KOH is often preferred.
Electrolysis
In the laboratory, with careful control of conditions, sodium
metal can be isolated from the electrolysis of the molten
monohydrate according to the following reaction:
4 NaOH·H2O(l) → 4 Na(l) + O2(g) + 6 H2O(g)
The monohydrate does not need to be heated in order
to melt, as the process produces enough heat due
to ohmic heating. However, it must be initiated with a
small quantity of liquid water to create an electrically
conductive electrolyte. As the system's temperature
increases, the monohydrate will start to melt at about 65
°C as stated above. Only when the temperature reaches
about 100 °C can sodium be isolated. Below this
temperature, the water produced will react with the
sodium, above this point, any water formed will be
driven off in the vapour phase, creating an essentially
anhydrous reaction. While this process has some
advantages over other electrolytic processes, it is not
preferred by most chemists for several reasons: a
marginal quantity of sodium produced boils at the
electrode interface, the vapour thus given off consists
primarily of fumed sodium oxide, which tends to settle
on any surface in close proximity with corrosive
consequences.
[edit]Production
Sodium hydroxide is industrially produced as a 50 %
solution by variations of the electrolytic chloralkali
process. Chlorine gas is also produced in this process.
Solid sodium hydroxide is obtained from this solution by
the evaporation of water. Solid sodium hydroxide is
most commonly sold as flakes, prills, and cast blocks.[1]
In 2004, world production was estimated at 60 million
dry metric tonnes of sodium hydroxide, and demand
was estimated at 51 million tonnes.[1] In 1998, total world
production was around 45 million tonnes. North America
and Asia collectively contributed around 14 million
tonnes, while Europe produced around 10 million
tonnes. In the United States, the major producer of
sodium hydroxide is the Dow Chemical Company, which
has annual production around 3.7 million tonnes from
sites at Freeport, Texas, and Plaquemine, Louisiana.
Other major US producers include Oxychem, PPG, Olin,
Pioneer Companies (which was purchased by Olin), Inc.
(PIONA), and Formosa. All of these companies use
the chloralkali process.[2]
Of historic interest is the Leblanc process, which
produced sodium carbonate, followed by roasting to
create carbon dioxide and sodium oxide, which readily
absorbs water to create sodium hydroxide. This method
is still occasionally used. It helped establish sodium
hydroxide as an important commodity chemical. The
Leblanc process was superseded by the Solvay
process in the late 19th century.
Sodium hydroxide may be formed by
the metathesis reaction between calcium hydroxide(also
known as lime) and sodium carbonate (also known as
soda ash):[3]
Ca(OH)2 + Na2CO3 → CaCO3 + 2 NaOH
[edit]Chloralkali electrolysis
Basic membrane cell used in theelectrolysis of brine.
Main article: Chloralkali process
Sodium hydroxide is produced (along
with chlorine and hydrogen) via the chloralkali
process. This involves the electrolysis of an
aqueous solution of sodium chloride. The sodium
hydroxide builds up at the cathode, where water is
reduced to hydrogen gas and hydroxide ion:
2 Na+ + 2 H2O + 2 e– → H2 + 2 NaOH
More accurately:
2 Na+Cl– + 2 H2O + 2 e– → H2 + 2 Cl– + 2 NaOH
The Cl– ions are oxidized to chlorine gas
at the anode.
To produce NaOH it is necessary to
prevent reaction of the NaOH with
the chlorine. This is typically done in one
of three ways, of which the membrane cell
process is economically the most viable.
Mercury cell process (also called
the Castner-Kellner process); sodium
ions are reduced to sodium metal,
which forms an amalgam with
a mercury cathode; this sodium is then
reacted with water to produce NaOH.
There have been concerns about
mercury releases, although modern
plants claim to be safe in this regard.[4]
Diaphragm cell process; uses a steel
cathode, and the reaction of NaOH
with Cl2 is prevented using a
porous diaphragm, often made
ofasbestos fibers. In the diaphragm
cell process the anode area is
separated from the cathode area by a
permeable diaphragm. The brine is
introduced into the anode
compartment and flows through the
diaphragm into the cathode
compartment. A diluted caustic brine
leaves the cell. The sodium hydroxide
must usually be concentrated to 50%
and the salt removed. This is done
using an evaporative process with
about three tonnes of steam per tonne
of sodium hydroxide. The salt
separated from the caustic brine can
be used to saturate diluted brine. The
chlorine contains oxygen and is
purified by liquefaction and
evaporation.[5][6]
Membrane cell process; similar to
the diaphragm cell process, with
a Nafion membrane to separate the
cathode and anode reactions. Only
sodium ions and a little water pass
through the membrane. It produces a
higher quality of NaOH. Of the three
processes, the membrane cell process
requires the lowest consumption of
electric energy and the amount of
steam needed for concentration of the
caustic is relatively small (less than
one tonne per tonne of sodium
hydroxide).[5][7]
[edit]Uses
Canister of sodium hydroxide.
Sodium hydroxide is the principal
strong base used in the chemical industry.
In bulk it is most often handled as
an aqueous solution, since solutions are
cheaper and easier to handle. Sodium
hydroxide, a strong base, is responsible
for most of these applications. Another
strong base such as potassium
hydroxide is likely to yield positive results
as well.
56 % of sodium hydroxide produced is
used by the chemical industry, with 25 %
of the same total used by the paper
industry. Sodium hydroxide is also used
for the manufacture of sodium salts and
detergents, for pH regulation, and for
organic synthesis. It is used in the Bayer
process of aluminium production.[1]
[edit]pH regulation
Sodium hydroxide is used in all sorts of
scenarios where it is desirable to increase
the alkalinity of a mixture, or to neutralize
acids.
For example, sodium hydroxide is used as
an additive in drilling mud to
increase alkalinity inbentonite mud
systems increases the mud viscosity, as
well as to neutralise any acid gas (such
as hydrogen sulfide and carbon dioxide)
which may be encountered in
the geological formation as drilling
progresses.
In the same industry, poor quality crude
oil can be treated with sodium hydroxide
to remove sulfurous impurities in a
process known ascaustic washing. As
above, sodium hydroxide reacts with weak
acids such as hydrogen sulfide and
mercaptans to give the non-volatile
sodium salts which can be removed. The
waste which is formed is toxic and difficult
to deal with, and the process is banned in
many countries because of this. In
2006, Trafigura used the process and
then dumped the waste in Africa.[8][9]
See also: hydrodesulfurization
[edit]Paper making
Main article: paper making
Sodium hydroxide was also widely used in
making paper. Along with sodium sulfide,
NaOH is a key component of the white
liquor solution used to
separate lignin from cellulose fibers in
the Kraft process. It also plays a key role
in several later stages of the process
of bleaching the brown pulp resulting from
the pulping process. These stages
include oxygen delignification, oxidative e
xtraction, and simple extraction, all of
which require a strong alkaline
environment with a pH > 10.5 at the end
of the stages.
[edit]Tissue digestion
In a similar fashion, sodium hydroxide is
used to digest tissues, such as in a
process that was used with farm animals
at one time. This process involves the
placing of a carcass into a sealed
chamber, which then puts the carcass in a
mixture of sodium hydroxide and water,
which breaks chemical bonds keeping the
body intact. This eventually turns the body
into a coffee-like[10][11] liquid, and the only
solid that remains are bone hulls, which
could be crushed between one's
fingertips.[12] Sodium hydroxide is
frequently used in the process of
decomposing roadkill dumped in landfills
by animal disposal contractors.[11] Sodium
hydroxide has also been used by
criminals to dispose of their victims'
bodies.[13]
[edit]Dissolving amphoteric metals and compounds
Strong bases attack aluminium. Sodium
hydroxide reacts with aluminium and
water to release hydrogen gas. The
aluminium takes the oxygen atom from
sodium hydroxide (NaOH), which in turn
takes the oxygen atom from the water,
and releases the two hydrogen atoms. In
this reaction, sodium hydroxide acts as an
agent to make the solution alkaline, which
aluminium can dissolve in. This reaction
can be useful in etching, removing
anodizing, or converting a polished
surface to a satin-like finish, but without
further passivation such
as anodizing oralodining the surface may
become degraded, either under normal
use or in severe atmospheric conditions.
In the Bayer process, sodium hydroxide is
used in the refining of alumina containing
ores (bauxite) to produce alumina
(aluminium oxide) which is the raw
material used to produce aluminium metal
via the electrolytic Hall-Héroult process.
Since the alumina is amphoteric, it
dissolves in the sodium hydroxide, leaving
impurities less soluble at high pH such
as iron oxides behind in the form of a
highly alkaline red mud.
See also: Ajka alumina plant accident
[edit]Esterification and transesterification reagent
Sodium hydroxide is traditionally used in
soap making (cold
process soap, saponification).[14] It was
made in the nineteenth century for a hard
surface rather than liquid product because
it was easier to store and transport.
For the manufacture of biodiesel, sodium
hydroxide is used as a catalyst for
the transesterification of methanol and
triglycerides. This only works
with anhydrous sodium hydroxide,
because combined with water the fat
would turn into soap, which would be
tainted with methanol. It is used more
often than potassium hydroxide because it
is cheaper and a smaller quantity is
needed.
[edit]Cleaning agent
Main article: Cleaning agent
Sodium hydroxide is frequently used as
an industrial cleaning agent where it is
often called "caustic". It is added to water,
heated, and then used to clean the
process equipment, storage tanks, etc. It
can
dissolve grease, oils, fats and protein bas
ed deposits. The sodium hydroxide
solution can also be added surfactants to
stabilize dissolved substances to prevent
redeposition. A sodium hydroxide soak
solution is used as a powerful degreaser
on stainless and glass bakeware. It is also
a common ingredient in oven cleaners.
A common use of sodium hydroxide is in
the production of parts washer detergents.
Parts washer detergents based on sodium
hydroxide are some of the most
aggressive parts washer cleaning
chemicals. The sodium hydroxide based
detergent include surfactants, rust
inhibitors and defoamers. A parts washer
heats water and the detergent in a closed
cabinet and then sprays the heated
sodium hydroxide and hot water at
pressure against dirty parts for degreasing
applications. Sodium hydroxide used in
this manner replaced many solvent based
systems in the early 1990s[citation
needed] when trichloroethane was outlawed
by the Montreal Protocol. Water and
sodium hydroxide detergent based parts
washers are considered to be an
environmental improvement over the
solvent based cleaning methods.
[edit]Food preparation
Food uses of sodium hydroxide include
washing or chemical peeling
of fruits and vegetables, chocolate and co
coa processing, caramel
coloring production, poultry scalding, soft
drink processing, and thickening ice
cream. Olives are often soaked in sodium
hydroxide to soften them,
while pretzels and German lye rolls are
glazed with a sodium hydroxide solution
before baking to make them crisp. Owing
to the difficulty in obtaining food grade
sodium hydroxide in small quantities for
home use, sodium carbonate is often
used in place of sodium hydroxide.[15]
Specific foods processed with sodium
hydroxide include:
The Pinoy or Filipino dessert (kakanin)
called kutsinta uses a bit of lye water
to help give the rice flour batter a jelly
like consistency.
A similar process is also used in the
kakanin known as pitsi-pitsi or pichi-
pichi (pit-chi-pit-chi) except that the
mixture uses gratedcassava instead of
rice flour.
The Scandinavian delicacy known
as lutefisk (from lutfisk, "lye fish").
Hominy is dried maize (corn) kernels
reconstituted by soaking in lye-water.
These expand considerably in size
and may be further processed by
frying to make corn nuts or by drying
and grinding to make grits. Nixtamal is
similar, but uses calcium
hydroxide instead of sodium
hydroxide.
Sodium hydroxide is also the chemical
that causes gelling of egg whites in the
production of Century eggs.
German pretzels are poached in a
boiling sodium carbonate solution or
cold sodium hydroxide solution before
baking, which contributes to their
unique crust.
Most yellow coloured Chinese
noodles are made with lye-water but
are commonly mistaken for containing
egg.
[edit]Domestic uses
Sodium hydroxide is used in the home as
a drain cleaning agent for clearing
clogged drains. It is distributed as a dry
crystal or as a thick liquid gel. The
chemical mechanism employed is the
conversion of grease to a form of soap.
Soap is water-soluble, and can be
dissolved by flushing with water. This
conversion occurs far more rapidly at high
temperatures, so commercial drain
cleaners may also contain chemicals that
react with water to generate heat. Sodium
hydroxide also decomposes complex
molecules such as the protein that
composeshair. Such drain cleaners (and
their acidic versions) are highly caustic
and should be handled with care.
Sodium hydroxide has been used as
a relaxer to straighten hair. However,
because of the high incidence and
intensity of chemical burns, chemical
relaxer manufacturers have now switched
to other alkaline chemicals. Sodium
hydroxide relaxers are still available, but
they are used mostly by professionals.
A solution of sodium hydroxide in water
was traditionally used as the most
common paint stripper on wooden objects.
Its use has become less common,
because it can damage the wood surface,
raising the grain and staining the colour.
[edit]Safety
Solid sodium hydroxide or solutions of
sodium hydroxide may cause chemical
burns, permanent injury or scarring if it
contacts unprotected human, or other
animal, tissue. It may cause blindness if it
contacts with the eye. Protective
equipment such as rubber gloves, safety
clothing and eye protection should always
be used when handling the material or its
solutions.
Dissolution of sodium hydroxide is
highly exothermic, and the resulting heat
may cause heat burns or ignite
flammables. It also produces heat when
reacted with acids. Sodium hydroxide is
corrosive to some metals, e.g. aluminum,
which produces flammable hydrogen gas
on contact. Sodium hydroxide is also
mildly corrosive to glass, which can cause
damage to glazing or freezing of ground
glass joints.
Preparation of Chlorine
Any of the methods listed below, can be used to prepare chlorine in the laboratory.
Sub Topics
1. From concentrated hydrochloric acid by oxidation
2. From Bleaching Powder [Ca(OCl)Cl]
3. Industrial Preparation of Chlorine
From concentrated hydrochloric acid by oxidationBack to Top
The apparatus is set up as shown in figure 14.3.
Chlorine can be prepared by the action of hot concentrated sulphuric acid on a mixture of a chloride salt and
an oxidising agent. Sodium chloride, being the cheapest and the most easily available chloride salt, is used
along with manganese dioxide as the oxidising agent.
A mixture of almost equal quantity of sodium chloride and manganese dioxide is taken in a round bottomed
flask. Concentrated sulphuric acid is then poured through the thistle funnel. The reaction takes place in two
stages. In the first stage sulphuric acid reacts with the chloride to form hydrochloric acid. In the second stage
the hydrochloric acid so formed combines with the oxidising agent to liberate chlorine.
(1)
(2) Manganese (II) chloride, formed during the reaction, reacts with sulphuric acid to form manganese (II)
sulphate and hydrochloric acid as under:
From Bleaching Powder [Ca(OCl)Cl]Back to Top
The apparatus is set up as shown in figure 14.5.
Chlorine can be prepared by removing the hydrogen from hydrochloric acid using an oxidizing agent. Any
oxidising agent such as manganese dioxide, lead dioxide, trilead tetroxide, potassium permanganate or
potassium dichromate can be used. Firstly, the oxidising agents are taken in the round bottomed flask.
Concentrated hydrochloric acid is then added through a thistle funnel. This mixture is then heated. The
oxygen of the oxidizing agents combines with the hydrogen of the hydrochloric acid leaving behind chlorine
i.e. hydrogen is removed from hydrochloric acid. The metallic ions of the oxidising agents combine with part
of chlorine to form the respective chlorides.
Remember:-
No heating is required in when potassium permanganate is used as an oxidizing agent in the above method
of preparing chlorine.
From sodium chloride, manganese dioxide and concentrated sulphuric acid
The apparatus is set up as shown in figure 14.4.
Bleaching powder is taken in a round bottom flask. Any dilute mineral acid is poured through the thistle
funnel. Chlorine can be prepared by dropping any acid on bleaching powder.
The chorine produced from hydrochloric acid by the above method, is passed through two wash
bottles. The first wash bottle contains water, to remove traces of hydrogen chloride gas from
chlorine. The second wash bottle contains concentrated sulphuric acid to dry the gas.
Industrial Preparation of ChlorineBack to Top
Chlorine is mostly obtained as a by-product during the manufacture of caustic soda, by the
electrolysis of brine or molten sodium chloride. Hence chlorine is rather prepared by cheap
methods. During this electrolysis, chlorine is liberated at the anode.
Remember:-
As chlorine is denser than air it is collected by the upward displacement of air.