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Hydrogen Peroxide: Is It Safe? And How to Use It! (modified at several places)
Also see: Hydrogen Peroxide Benefits
From a chemical standpoint, hydrogen peroxide is the simplest peroxide. It's a compound with an oxygen-oxygen single bond. Its chemical usage is as an oxidizer, bleaching agent, and disinfectant. However, in the past several years, hydrogen peroxide has shown it can do much more, from a simple mouthwash to even healing some health conditions.
Hydrogen peroxide, therefore, deserves a place in every home. As the only germicidal agent composed only of oxygen and water, it's considered one of the world's safest, all-natural sanitizers. With that in mind, let's take a look at everything you can do with hydrogen peroxide.
Hydrogen Peroxide in Ear
One of the much-discussed topics regarding hydrogen peroxide is its usage for cleaning ear wax. Some people believe it's safe; others claim it's dangerous. In any case, ear wax is what protects your inner ear from dirt and foreign matter. Too much of it can affect your hearing and cause pain, itching, and general dizziness. Hydrogen peroxide can help you clean moderate or mild amounts of ear wax.
If you clean your ears regularly, you'll prevent hard buildup, which can trap bacteria in the inner ear. For the hydrogen peroxide treatment, you'll need a towel, a bowl, and a 3% hydrogen peroxide solution.
Here's how to do it.
Step 1
Start by pulling your hair back. Then cover your head with a towel or a hat (to prevent hair lightening or discoloration from the bleaching properties of hydrogen peroxide). You want to protect your hair before starting the treatment.
Step 2
Lie down on your left side, using a pillow to make it more comfortable (make sure to cover your pillow with a clean towel so that you catch any excess fluid that might come out of your ear). Use a flat or low loft pillow to keep the head level, so your ear is parallel to the ceiling. Only by doing this can the hydrogen peroxide penetrate deep enough and prevent drainage coming out of the ear.
Step 3
Pour hydrogen peroxide into your right ear. Initially, you'll experience fizzing or pouring sounds. You might also feel a deep itch inside your ear. Don't worry; it's nothing serious. It's just the sign that the hydrogen peroxide is activated and breaking down the wax buildup.
Step 4
Lie still and let the hydrogen peroxide work its magic for the next 20 minutes. Stay in the resting position. As time goes by, the fizzing and popping sounds will become less intense and frequent. Just be patient and let a few minutes pass.
Step 5
Stand up, tilt your head to the right, and allow the solution to drain from the ear. Make sure to keep a bowl or towel under your ear as the solution drains (you don't want to make a mess in your home!). You might notice small pieces of wax coming out of your ear as well.
Step 6
Using the towel, dry the outside of your ear. Once your ear is completely dry, repeat the process on the left side. This time, rest on your right side. Make sure to cover your pillow with a clean towel so that you catch any excess fluid that might come out of your ear.
Warnings and precautions
While some similar guides might recommend using cotton swabs, cotton balls, and hairpins, don't use them. Using any of these might cause damage to your eardrum or allow bacteria to enter your ear canal.
If you experience changes in your hearing after you try the treatment, consult your physician. Don't repeat the treatment procedure too often. If you clean your ears frequently with hydrogen peroxide, you might experience itching and dryness in the inner ear. Or even worse—bacterial infections.
During the cleaning process, keep your fingers out of your ear, even if you notice itching. Your fingers might carry germs, and you might cause an ear infection without realizing it. Never dip or soak contaminated clothes, fingers, or other objects in the peroxide bottle, which will contaminate the contents of the container.
What science says
There are always two sides to a story. In terms of ear wax cleaning, some people claim that the solution isn't safe. However, scientific studies show that hydrogen peroxide is one of the most reliable and effective treatments for ear wax.
For example, a 2004 study showed that while earwax irrigation is a standard treatment, eardrops (usually made with hydrogen peroxide) are the most cost-effective way to treat the condition. Ear drops use hydrogen peroxide to soften the wax.
Another study, from 2015 and Australia, showed that using water only to remove the wax can lead to complications. Therefore, eardrops are again recommended, as they have less room for error.
Food-Grade Hydrogen Peroxide
Another common and problematic area for hydrogen peroxide is food. Or in other words, is there a grade of hydrogen peroxide that is safe for home usage?
Let's examine the question.
What is food-grade hydrogen peroxide?
As we learned before, hydrogen peroxide is a substance comprised of two hydrogen atoms and two oxygen atoms. The chemical sign is H2O2. Because of its chemical composure, hydrogen peroxide is easily broken down, resulting in water and oxygen.
There are different grades of hydrogen peroxide made for specific usages. For example, an electrical class of the solution includes chemical stabilizers that prevent it from decomposing. The food-grade of hydrogen peroxide has a concentration of 35% and is more potent than what is usually sold in stores.
The benefits of this solution are that you get an effective and natural disinfectant. During the process of oxidization, the substance eliminates toxins and any other pathogens in the body.
What does food-grade hydrogen peroxide cure?
Let's take a quick look at all of the benefits of food-grade hydrogen peroxide. There are several ways you can use it to support your health. We'll look at the many uses of hydrogen peroxide later on, but for now, here is a quick breakdown:
How to use food-grade hydrogen peroxide
The standard hydrogen peroxide offers a safe and natural treatment. But that's a product with only a 3% solution. Food-grade hydrogen peroxide must be diluted prior to use. If not, it might cause health problems.
Food-grade hydrogen peroxide is a 35% solution intended for use in preparing or storing food.
Dangers and side effects
Most folk remedies with hydrogen peroxide are safe, and there are no side effects when you use the appropriate dosage of 4 drops per 8 ounces of distilled water. However, here are some problems that might occur.
For example, food-grade hydrogen peroxide can damage the gastrointestinal tract. Such happens if you accidentally consume a high dose of food-grade hydrogen peroxide. Never mistake it for water. Ingesting the substance can lead to many accidents and even worse side effects.
Hydrogen peroxide in the body can release dangerous amounts of oxygen. Rapid release of the gas can cause the perforation of the stomach and intestines. While oxygen is beneficial and welcomed, excessive amounts in the bloodstream can lead to a gas embolism.
Uses of Hydrogen Peroxide
Health and beauty
Home and kitchen
Hydrogen peroxide
From Wikipedia, the free encyclopedia
Hydrogen peroxide is a chemical compound with the formula H2O2. In its pure form, it is a very pale blue [5] liquid, slightly more viscous than water. Hydrogen peroxide is the simplest peroxide (a compound with an oxygen–oxygen single bond). It is used as an oxidizer, bleaching agent, and antiseptic. Concentrated hydrogen peroxide, or "high-test peroxide", is a reactive oxygen species and has been used as a propellant in rocketry.[6] Its chemistry is dominated by the nature of its unstable peroxide bond.
Hydrogen peroxide is unstable and slowly decomposes in the presence of light. Because of its instability, hydrogen peroxide is typically stored with a stabilizer in a weakly acidic solution in a dark coloured bottle. Hydrogen peroxide is found in biological systems including the human body. Enzymes that use or decompose hydrogen peroxide are classified as peroxidases.
Properties
The boiling point of H2O2 has been extrapolated as being 150.2 °C, approximately 50 °C higher than water. In practice, hydrogen peroxide will undergo potentially explosive thermal decomposition if heated to this temperature. It may be safely distilled at lower temperatures under reduced pressure.[7]
Structure
Structure and dimensions of H2O2 in the gas phase
Structure and dimensions of H2O2 in the solid (crystalline) phaseHydrogen peroxide (H2O2) is a nonplanar molecule with (twisted) C2 symmetry; this was first shown by Paul-Antoine Giguère in 1950 using infrared spectroscopy.[8][9] Although the O−O bond is a single bond, the molecule has a relatively high rotational barrier of 2460 cm−1 (29.45 kJ/mol);[10] for comparison, the rotational barrier for ethane is 12.5 kJ/mol. The increased barrier is ascribed to repulsion between the lone pairs of the adjacent oxygen atoms and results in hydrogen peroxide displaying atropisomerism.
The molecular structures of gaseous and crystalline H2O2 are significantly different. This difference is attributed to the effects of hydrogen bonding, which is absent in the gaseous state.[11] Crystals of H2O2 are tetragonal with the space group D44P4121.[12]
Aqueous solutions
In aqueous solutions hydrogen peroxide differs from the pure substance due to the effects of hydrogen bonding between water and hydrogen peroxide molecules. Hydrogen peroxide and water form a eutectic mixture, exhibiting freezing-point depression down as low as -56°C; pure water has a freezing point of 0 °C and pure hydrogen peroxide of −0.43 °C. The boiling point of the same mixtures is also depressed in relation with the mean of both boiling points (125.1 °C). It occurs at 114 °C. This boiling point is 14 °C greater than that of pure water and 36.2 °C less than that of pure hydrogen peroxide.[13]
Phase diagram of H2O2 and water: Area above blue line is liquid. Dotted lines separate solid+liquid phases from solid+solid phases.
Comparison with analogues
Hydrogen peroxide has several structural analogues with Hm−X−X−Hn bonding arrangements (water also shown for comparison). It has the highest (theoretical) boiling point of this series (X = O, N, S). Its melting point is also fairly high, being comparable to that of hydrazine and water, with only hydroxylamine crystallising significantly more readily, indicative of particularly strong hydrogen bonding. Diphosphane and hydrogen disulfide exhibit only weak hydrogen bonding and have little chemical similarity to hydrogen peroxide. All of these analogues are thermodynamically unstable. Structurally, the analogues all adopt similar skewed structures, due to repulsion between adjacent lone pairs.
Discovery
Alexander von Humboldt reported one of the first synthetic peroxides, barium peroxide, in 1799 as a by-product of his attempts to decompose air.
Nineteen years later Louis Jacques Thénard recognized that this compound could be used for the preparation of a previously unknown compound, which he described as eau oxygénée (French: oxygenated water) – subsequently known as hydrogen peroxide.[14][15][16] Today this term refers instead to water containing dissolved oxygen (O2).
An improved version of Thénard's process used hydrochloric acid, followed by addition of sulfuric acid to precipitate the barium sulfate byproduct. This process was used from the end of the 19th century until the middle of the 20th century.[17]
Thénard and Joseph Louis Gay-Lussac synthesized sodium peroxide in 1811. The bleaching effect of peroxides and their salts on natural dyes became known around that time, but early attempts of industrial production of peroxides failed. The first plant producing hydrogen peroxide was built in 1873 in Berlin. The discovery of the synthesis of hydrogen peroxide by electrolysis with sulfuric acid introduced the more efficient electrochemical method. It was first commercialized in 1908 in Weißenstein, Carinthia, Austria. The anthraquinone process, which is still used, was developed during the 1930s by the German chemical manufacturer IG Farben in Ludwigshafen. The increased demand and improvements in the synthesis methods resulted in the rise of the annual production of hydrogen peroxide from 35,000 tonnes in 1950, to over 100,000 tonnes in 1960, to 300,000 tonnes by 1970; by 1998 it reached 2.7 million tonnes.[18]
Pure hydrogen peroxide was long believed to be unstable, as early attempts to separate it from the water, which is present during synthesis, all failed. This instability was due to traces of impurities (transition-metal salts), which catalyze the decomposition of the hydrogen peroxide. Pure hydrogen peroxide was first obtained in 1894—almost 80 years after its discovery—by Richard Wolffenstein, who produced it by vacuum distillation.[19]
Determination of the molecular structure of hydrogen peroxide proved to be very difficult. In 1892 the Italian physical chemist Giacomo Carrara (1864–1925) determined its molecular mass by freezing-point depression, which confirmed that its molecular formula is H2O2.[20] At least half a dozen hypothetical molecular structures seemed to be consistent with the available evidence.[21] In 1934, the English mathematical physicist William Penney and the Scottish physicist Gordon Sutherland proposed a molecular structure for hydrogen peroxide that was very similar to the presently accepted one.[22]
Previously, hydrogen peroxide was prepared industrially by hydrolysis of ammonium persulfate,[citation needed] which was itself obtained by the electrolysis of a solution of ammonium bisulfate (NH4HSO4) in sulfuric acid:
(NH4)2S2O8 + 2 H2O → H2O2 + 2 (NH4)HSO4
Production
Catalytic cycle for the anthraquinone process to produce hydrogen peroxide
Today, hydrogen peroxide is manufactured almost exclusively by the anthraquinone process, which was formalized in 1936 and patented in 1939. It begins with the reduction of an anthraquinone (such as 2-ethylanthraquinone or the 2-amyl derivative) to the corresponding anthrahydroquinone, typically by hydrogenation on a palladium catalyst. In the presence of oxygen, the anthrahydroquinone then undergoes autoxidation: the labile hydrogen atoms of the hydroxy groups transfer to the oxygen molecule, to give hydrogen peroxide and regenerating the anthraquinone. Most commercial processes achieve oxidation by bubbling compressed air through a solution of the anthrahydroquinone, with the hydrogen peroxide then extracted from the solution and the anthraquinone recycled back for successive cycles of hydrogenation and oxidation.[23][24]
The net reaction for the anthraquinone-catalyzed process is :[23]
H2 + O2 → H2O2The economics of the process depend heavily on effective recycling of the extraction solvents, the hydrogenation catalyst and the expensive quinone.
Minute but detectable amounts of hydrogen peroxide can be formed by several methods. Small amounts are formed by electrolysis of dilute acid around the cathode where hydrogen evolves if oxygen is bubbled around it. It is also produced by exposing water to ultraviolet rays from a mercury lamp, sunlight (this needs an edit, UV from Mercury lamps and electric arcs cause UV C - the shortest wavelength of UV - and UV C from the sun doesn't pass through our atmosphere. T he reference used for this section is from 1922 and possible outdated), or an electric arc while confining it in a UV transparent vessel (e.g. quartz). It is detectable in ice water after burning a hydrogen gas stream aimed towards it and is also detectable on floating ice. Rapidly cooling humid air blown through an approximately 2000°C spark gap results in detectable amounts.[25]
A commercially viable process to produce hydrogen peroxide directly from the elements has been of interest for many years. Efficient direct synthesis is difficult to achieve, as the reaction of hydrogen with oxygen thermodynamically favours production of water. Systems for direct synthesis have been developed, most of which employ finely dispersed metal catalysts similar to those used for hydrogenation of organic substrates.[26][27] None of these has yet reached a point where they can be used for industrial-scale synthesis.
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; 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 more than 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 allow inspection by commercial manufacturers.
In 1994, world production of H2O2 was around 1.9 million tonnes and grew to 2.2 million in 2006,[28] most of which was at a concentration of 70% or less. In that year bulk 30% H2O2 sold for around 0.54 USD/kg, equivalent to US$1.50/kg (US$0.68/lb) on a "100% basis".[29]
Hydrogen peroxide occurs in surface water, groundwater and in the atmosphere. It forms upon illumination or natural catalytic action by substances contained in water. Sea water contains 0.5 to 14 μg/L of hydrogen peroxide, freshwater 1 to 30 μg/L and air 0.1 to 1 parts per billion.[18]
Reactions
Decomposition
Hydrogen peroxide is thermodynamically unstable and decomposes to form water and oxygen with a ΔHo of -2884.5 kJ/kg[30] and a ΔS of 70.5 J/(mol·K):
2 H2O2 → 2 H2O + O2
The rate of decomposition increases with rise in temperature, concentration, and pH, with cool, dilute, acidic solutions showing the best stability. Decomposition is catalysed by various compounds, including most transition metals and their compounds (e.g. manganese dioxide (MnO2), silver, and platinum).[31] Certain metal ions, such as Fe2+ or Ti3+, can cause the decomposition to take a different path, with free radicals such as the hydroxyl radical (HO·) and hydroperoxyl (HOO·) being formed. Non-metallic catalysts include potassium iodide, which reacts particularly rapidly and forms the basis of the elephant toothpaste demonstration. Hydrogen peroxide can also be decomposed biologically by the enzyme catalase. The decomposition of hydrogen peroxide liberates oxygen and heat; this can be dangerous, as spilling high-concentration hydrogen peroxide on a flammable substance can cause an immediate fire.
Redox reactions
The redox properties of hydrogen peroxide depend on pH.
In acidic solutions, H2O2 is a powerful oxidizer,stronger than chlorine, chlorine dioxide, and potassium permanganate. When used for cleaning laboratory glassware, a solution of hydrogen peroxide and sulfuric acid is referred to as Piranha solution.
H2O2 is a source of hydroxyl radicals (·OH), which are highly reactive. H2O2 is used in the spectacular Briggs-Rauscher[32][33] and Bray-Liebhafsky [34] [35]oscillating reactions.
Oxidant Reduced product Oxidation
potential
(V)
F2 HF 3.0
O3 O2 2.1
H2O2 H2O 1.8
KMnO4 MnO2 1.7
ClO2 HClO 1.5
Cl2 Cl− 1.4
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) + 2 H2O(l)
and sulfite (SO2−3) is oxidized to sulfate (SO2−4). 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).
In basic solution, hydrogen peroxide can reduce a variety of inorganic ions. When it acts as a reducing agent, oxygen gas is also produced. For example, hydrogen peroxide will reduce sodium hypochlorite and potassium permanganate, which is a convenient method for preparing oxygen in the laboratory:
NaOCl + H2O2 → O2 + NaCl + H2O2
KMnO4 + 3 H2O2 → 2 MnO2 + 2 KOH + 2 H2O + 3 O2
Organic reactions
Hydrogen peroxide is frequently used as an oxidizing agent. Illustrative is oxidation of thioethers to sulfoxides:[36][37]
Ph−S−CH3 + H2O2 → Ph−S(O)−CH3 + H2O
Alkaline hydrogen peroxide is used for epoxidation of electron-deficient alkenes such as acrylic acid derivatives,[38] and for the oxidation of alkylboranes to alcohols, the second step of hydroboration-oxidation. It is also the principal reagent in the Dakin oxidation process.
Precursor to other peroxide compounds
Hydrogen peroxide is a weak acid, forming hydroperoxide or peroxide salts with many metals.
It also converts metal oxides into the corresponding peroxides. For example, upon treatment with hydrogen peroxide, chromic acid (CrO3 + H2SO4) forms an unstable blue peroxide CrO(O2)2.
This kind of reaction is used industrially to produce peroxoanions. 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 (RCO2H) into peroxy acids (RC(O)O2H), which are themselves used as oxidizing agents. Hydrogen peroxide reacts with acetone to form acetone peroxide and with ozone to form trioxidane. Hydrogen peroxide forms stable adducts with urea (Hydrogen peroxide - urea), sodium carbonate (sodium percarbonate) and other compounds.[39] An acid-base adduct with triphenylphosphine oxide is a useful "carrier" for H2O2 in some reactions.
Hydrogen peroxide is both an oxidizing agent and reducing agent. The oxidation of hydrogen peroxide by sodium hypochlorite yields singlet oxygen. The net reaction of a ferric ion with hydrogen peroxide is a ferrous ion and oxygen. This proceeds via single electron oxidation and hydroxyl radicals. This is used in some organic chemistry oxidations, e.g. in the Fenton's reagent. Only catalytic quantities of iron ion is needed since peroxide also oxidizes ferrous to ferric ion. The net reaction of hydrogen peroxide and permanganate or manganese dioxide is manganous ion; however, until the peroxide is spent some manganous ions are reoxidized to make the reaction catalytic. This forms the basis for common monopropellant rockets.
Biological function
Hydrogen peroxide is formed in humans and other animals as a short-lived product in biochemical processes and is toxic to cells. The toxicity is due to oxidation of proteins, membrane lipids and DNA by the peroxide ions.[40] The class of biological enzymes called superoxide dismutase (SOD) is developed in nearly all living cells as an important antioxidant agent. They promote the disproportionation of superoxide into oxygen and hydrogen peroxide, which is then rapidly decomposed by the enzyme catalase to oxygen and water.[41]
2 O−2 + 2 H+ → H2O2 + O2
Peroxisomes are organelles found in virtually all eukaryotic cells.[42] They are involved in the catabolism of very long chain fatty acids, branched chain fatty acids, D-amino acids, polyamines, and biosynthesis of plasmalogens, etherphospholipids critical for the normal function of mammalian brains and lungs.[43] Upon oxidation, they produce hydrogen peroxide in the following process:[44]
{\displaystyle {\ce {R-CH2-CH2-CO-SCoA + O2 ->[{\ce {FAD}}] R-CH=CH-CO-SCoA + H2O2}}}
FAD = flavin adenine dinucleotideCatalase,
another peroxisomal enzyme, uses this H2O2 to oxidize other substrates, including phenols, formic acid, formaldehyde, and alcohol, by means of the peroxidation reaction:
{\displaystyle {\ce {H2O2 + R'H2 -> R' + 2H2O}}}, thus eliminating the poisonous hydrogen peroxide in the process.This reaction is important in liver and kidney cells, where the peroxisomes neutralize various toxic substances that enter the blood. Some of the ethanol humans drink is oxidized to acetaldehyde in this way.[45] In addition, when excess H2O2 accumulates in the cell, catalase converts it to H2O through this reaction:
{\displaystyle {\ce {H2O2 ->[{\ce {CAT}}] {1/2O2}+ H2O}}}Another origin of hydrogen peroxide is the degradation of adenosine monophosphate which yields hypoxanthine. Hypoxanthine is then oxidatively catabolized first to xanthine and then to uric acid, and the reaction is catalyzed by the enzyme xanthine oxidase:[46]
Hypoxanthine
Xanthine oxidase
H
2O, O2
H2O2
Xanthine
Xanthine oxidase
H
2O, O2
H2O2
Uric acid
Degradation of hypoxanthine through xanthine to uric acid to form hydrogen peroxide.
Australian bombardier beetleThe degradation of guanosine monophosphate yields xanthine as an intermediate product which is then converted in the same way to uric acid with the formation of hydrogen peroxide.[46]
Eggs of sea urchin, shortly after fertilization by a sperm, produce hydrogen peroxide. It is then quickly dissociated to OH· radicals. The radicals serve as initiator of radical polymerization, which surrounds the eggs with a protective layer of polymer.[47]
The bombardier beetle has a device which allows it to shoot corrosive and foul-smelling bubbles at its enemies. The beetle produces and stores hydroquinone and hydrogen peroxide, in two separate reservoirs in the rear tip of its abdomen. When threatened, the beetle contracts muscles that force the two reactants through valved tubes into a mixing chamber containing water and a mixture of catalytic enzymes. When combined, the reactants undergo a violent exothermic chemical reaction, raising the temperature to near the boiling point of water. The boiling, foul-smelling liquid partially becomes a gas (flash evaporation) and is expelled through an outlet valve with a loud popping sound.[48][49][50]
Hydrogen peroxide is a signaling molecule of plant defense against pathogens.[51]
Hydrogen peroxide has roles as a signalling molecule in the regulation of a wide variety of biological processes.[52] The compound is a major factor implicated in the free-radical theory of aging, based on how readily hydrogen peroxide can decompose into a hydroxyl radical and how superoxide radical byproducts of cellular metabolism can react with ambient water to form hydrogen peroxide.[53] These hydroxyl radicals in turn readily react with and damage vital cellular components, especially those of the mitochondria.[54][55][56] At least one study has also tried to link hydrogen peroxide production to cancer.[57] These studies have frequently been quoted in fraudulent treatment claims.[citation needed]
The amount of hydrogen peroxide in biological systems can be assayed using a fluorometric assay.[58]
UsesBleachingAbout 60% of the world's production of hydrogen peroxide is used for pulp- and paper-bleaching.[28]. The second major industrial application is the manufacture of sodium percarbonate and sodium perborate, which are used as mild bleaches in laundry detergents. Sodium percarbonate, which is an adduct of sodium carbonate and hydrogen peroxide, is the active ingredient in such laundry products as OxiClean and Tide laundry detergent. When dissolved in water, it releases hydrogen peroxide and sodium carbonate,[59] By themselves these bleaching agents are only effective at wash temperatures of 60 °C (140 °F) or above and so, often are used in conjunction with bleach activators, which facilitate cleaning at lower temperatures.
Production of organic compoundsIt is used in the production of various organic peroxides with dibenzoyl peroxide being a high volume example. It is used in polymerisations, as a flour bleaching agent, and as a treatment for acne. Peroxy acids, such as peracetic acid and meta-chloroperoxybenzoic acid also are produced using hydrogen peroxide. Hydrogen peroxide has been used for creating organic peroxide-based explosives, such as acetone peroxide.
Disinfectant
Skin shortly after exposure to 35% H2O2
Contact lenses soaking in a 3% hydrogen peroxide-based solution. The case includes a catalytic disc which neutralises the hydrogen peroxide over time.Hydrogen peroxide is used in certain waste-water treatment processes to remove organic impurities. In advanced oxidation processing, the Fenton reaction[60][61] gives the highly reactive hydroxyl radical (·OH). This degrades organic compounds, including those that are ordinarily robust, such as aromatic or halogenated compounds.[62] It can also oxidize sulfur based compounds present in the waste; which is beneficial as it generally reduces their odour.[63]
Hydrogen peroxide may be used for the sterilization of various surfaces,[64] including surgical tools,[65] and may be deployed as a vapour (VHP) for room sterilization.[66] H2O2 demonstrates broad-spectrum efficacy against viruses, bacteria, yeasts, and bacterial spores.[67][68] In general, greater activity is seen against Gram-positive than Gram-negative bacteria; however, the presence of catalase or other peroxidases in these organisms may increase tolerance in the presence of lower concentrations.[69] Lower levels of concentration (3%) will work against most spores; higher concentrations (7 to 30%) and longer contact times will improve sporicidal activity.[68][70]
Hydrogen peroxide is seen as an environmentally safe alternative to chlorine-based bleaches, as it degrades to form oxygen and water and it is generally recognized as safe as an antimicrobial agent by the U.S. Food and Drug Administration (FDA).[71]
Hydrogen peroxide may be used to treat acne,[72] although benzoyl peroxide is a more common treatment.
Niche uses[edit]
Chemiluminescence of cyalume, as found in a glow stickHydrogen peroxide has various domestic uses, primarily as a cleaning and disinfecting agent.
Hair bleachingDiluted H
2O
2 (between 1.9% and 12%) mixed with aqueous ammonia has been used to bleach human hair. The chemical's bleaching property lends its name to the phrase "peroxide blonde".[73] Hydrogen peroxide is also used for tooth whitening. It may be found in most whitening toothpastes. Hydrogen peroxide has shown positive results involving teeth lightness and chroma shade parameters.[citation needed] It works by oxidizing colored pigments onto the enamel where the shade of the tooth may become lighter.[further explanation needed] Hydrogen peroxide may be mixed with baking soda and salt to make a home-made toothpaste.[74]
Propellant
Further information: High-test peroxide
Rocket-belt hydrogen-peroxide propulsion system used in a jet packHigh-concentration H
2O
2 is referred to as "high-test peroxide" (HTP). 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 (1,112 °F), which is expelled through a nozzle, generating thrust. H
2O
2 monopropellant produces a maximal specific impulse (Isp) of 161 s (1.6 kN·s/kg). Peroxide was the first major monopropellant adopted for use in rocket applications. Hydrazine eventually replaced hydrogen-peroxide monopropellant thruster applications primarily because of a 25% increase in the vacuum specific impulse.[75] Hydrazine (toxic) and hydrogen peroxide (less-toxic [ACGIH TLV 0.01 and 1 ppm respectively]) are the only two monopropellants (other than cold gases) to have been widely adopted and utilized for propulsion and power applications.[citation needed] The Bell Rocket Belt, reaction control systems for X-1, X-15, Centaur, Mercury, Little Joe, as well as the turbo-pump gas generators for X-1, X-15, Jupiter, Redstone and Viking used hydrogen peroxide as a monopropellant.[76]
As a bipropellant, H
2O
2 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 may also be used for regenerative cooling of rocket engines. Peroxide was used very successfully as an oxidizer in World War II German rocket motors (e.g. T-Stoff, containing oxyquinoline stabilizer, for both the Walter HWK 109-500 Starthilfe RATO externally podded monopropellant booster system, and for the Walter HWK 109-509 rocket motor series used for the Me 163B), most often used with C-Stoff in a self-igniting hypergolic combination, and for the low-cost British Black Knight and Black Arrow launchers.
In the 1940s and 1950s, the Hellmuth Walter KG-conceived 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. Operator error in the use of hydrogen-peroxide torpedoes was named as possible causes for the sinkings of HMS Sidon and the Russian submarine Kursk.[77] 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.[78][79]
Glow sticksHydrogen peroxide reacts with certain di-esters, such as phenyl oxalate ester (cyalume), to produce chemiluminescence; this application is most commonly encountered in the form of glow sticks.
HorticultureSome 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.[80][81]
FishkeepingHydrogen peroxide is used in aquaculture for controlling mortality caused by various microbes. In 2019, the U.S. FDA approved it for control of Saprolegniasis in all coldwater finfish and all fingerling and adult coolwater and warmwater finfish, for control of external columnaris disease in warm-water finfish, and for control of Gyrodactylus spp. in freshwater-reared salmonids.[82] Laboratory tests conducted by fish culturists have demonstrated that common household hydrogen peroxide may be used safely to provide oxygen for small fish. The hydrogen peroxide releases oxygen by decomposition when it is exposed to catalysts such as manganese dioxide.
Safety[edit]Regulations vary, but low concentrations, such as 6%, are widely available and legal to buy for medical use. Most over-the-counter peroxide solutions are not suitable for ingestion. Higher concentrations may be considered hazardous and typically are accompanied by a Safety data sheet (SDS). 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
2O
2 will react violently.[83]
High-concentration hydrogen peroxide streams, typically above 40%, should be considered hazardous 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 (45 kg), or approximately 10 US gallons (38 L), of concentrated hydrogen peroxide.
Hydrogen peroxide should be stored in a cool, dry, well-ventilated area and away from any flammable or combustible substances. 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).[84] 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 block light.[85]
Hydrogen peroxide, either in pure or diluted form, may pose several risks, the main one being that it forms explosive mixtures upon contact with organic compounds.[86] Highly concentrated hydrogen peroxide is unstable and may cause a boiling liquid expanding vapour explosion (BLEVE) of the remaining liquid. Consequently, distillation of hydrogen peroxide at normal pressures is highly dangerous. It is also corrosive, especially when concentrated, but even domestic-strength solutions may cause irritation to the eyes, mucous membranes, and skin.[87] Swallowing hydrogen peroxide solutions is particularly dangerous, as decomposition in the stomach releases large quantities of gas (ten times the volume of a 3% solution), leading to internal bloating. Inhaling over 10% can cause severe pulmonary irritation.[88]
With a significant vapour pressure (1.2 kPa at 50 °C[89]), hydrogen-peroxide vapour is potentially hazardous. According to U.S. NIOSH, the immediately dangerous to life and health (IDLH) limit is only 75 ppm.[90] The U.S. Occupational Safety and Health Administration (OSHA) has established a permissible exposure limit of 1.0 ppm calculated as an 8-hour time-weighted average (29 CFR 1910.1000, Table Z-1).[86] Hydrogen peroxide also has been classified by the American Conference of Governmental Industrial Hygienists (ACGIH) as a "known animal carcinogen, with unknown relevance on humans".[91] For workplaces where there is a risk of exposure to the hazardous concentrations of the vapours, continuous monitors for hydrogen peroxide should be used. Information on the hazards of hydrogen peroxide is available from OSHA [86] and from the ATSDR.[92]
Adverse effects on wounds[edit]Historically hydrogen peroxide was used for disinfecting wounds, partly because of its low cost and prompt availability compared to other antiseptics. Now[when?] it is thought to inhibit healing and to induce scarring, because it destroys newly formed skin cells.[93] One study found that only very low concentrations (0.03% solution, this is a dilution of typical 3% Peroxide by 100 times) may induce healing, and only if not applied repeatedly. A 0.5% solution was found to impede healing.[94] Surgical use can lead to gas embolism formation.[95][96] Despite this, it is still used for wound treatment in many countries, and, in the United States, is prevalent as a major first aid antiseptic.[97][98]
Dermal exposure to dilute solutions of hydrogen peroxide causes whitening or bleaching of the skin due to microembolism caused by oxygen bubbles in the capillaries.[99]
Use in alternative medicine[edit]Practitioners of alternative medicine have advocated the use of hydrogen peroxide for various conditions, including emphysema, influenza, AIDS, and in particular cancer.[100] There is no evidence of effectiveness and in some cases it has proved fatal.[101][102][103][104][105]
The practice calls for the daily consumption of hydrogen peroxide, either orally or by injection, and is based on two precepts. First, that hydrogen peroxide is produced naturally by the body to combat infection; and second, that human pathogens (including cancer: See Warburg hypothesis) are anaerobic and cannot survive in oxygen-rich environments. The ingestion or injection of hydrogen peroxide therefore is believed to kill disease by mimicking the immune response in addition to increasing levels of oxygen within the body. This makes the practice similar to other oxygen-based therapies, such as ozone therapy and hyperbaric oxygen therapy.
Both the effectiveness and safety of hydrogen peroxide therapy is scientifically questionable. Hydrogen peroxide is produced by the immune system, but in a carefully controlled manner. Cells called phagocytes engulf pathogens and then use hydrogen peroxide to destroy them. The peroxide is toxic to both the cell and the pathogen and so is kept within a special compartment, called a phagosome. Free hydrogen peroxide will damage any tissue it encounters via oxidative stress, a process that also has been proposed as a cause of cancer.[106] Claims that hydrogen peroxide therapy increases cellular levels of oxygen have not been supported. The quantities administered would be expected to provide very little additional oxygen compared to that available from normal respiration. It is also difficult to raise the level of oxygen around cancer cells within a tumour, as the blood supply tends to be poor, a situation known as tumor hypoxia.
Large oral doses of hydrogen peroxide at a 3% concentration may cause irritation and blistering to the mouth, throat, and abdomen as well as abdominal pain, vomiting, and diarrhea.[101] Intravenous injection of hydrogen peroxide has been linked to several deaths.[103][104][105] The American Cancer Society states that "there is no scientific evidence that hydrogen peroxide is a safe, effective, or useful cancer treatment."[102] Furthermore, the therapy is not approved by the U.S. FDA.
Historical incidents[edit]
See also
References
Notes
Bibliography
