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Hydrogen peroxide (hydrogen peroxide), 2 2 - the simplest representative of peroxides. Colorless liquid with a "metallic" taste, infinitely soluble in water, alcohol and ether. Concentrated aqueous solutions are explosive. Hydrogen peroxide is a good solvent. It is released from water in the form of an unstable crystalline hydrate H 2 O 2 2H 2 O.
The hydrogen peroxide molecule has the following structure:
Physical Properties
Pure hydrogen peroxide is very different from the familiar 3% solution of H 2 O 2 that is in the home first aid kit. First of all, it is almost one and a half times heavier than water (density at 20 ° C is 1.45 g/cm3). H 2 O 2 freezes at a temperature slightly lower than the freezing point of water - at minus 0.41 ° C, but if you quickly cool a clean liquid, it usually does not freeze, but supercools, turning into a transparent glassy mass. H 2 O 2 solutions freeze at a much lower temperature: a 30% solution at minus 30 ° C, and a 60% solution at minus 53 ° C. H 2 O 2 boils at a temperature higher than ordinary water, - at 150.2 ° C. It wets glass with H 2 O 2 worse than water, and this leads to an interesting phenomenon in the slow distillation of aqueous solutions: while water is distilled from the solution, it, as usual, enters from the refrigerator into the receiver in the form of drops ; when H 2 O 2 begins to distill, the liquid leaves the refrigerator in the form of a continuous thin stream. On the skin, pure hydrogen peroxide and its concentrated solutions leave white spots and cause a sensation of burning pain due to a severe chemical burn.
Pure H 2 O 2, like sugar syrup, strongly refracts light. Indeed, the refractive index of anhydrous H 2 O 2 (1.41) is much greater than that of water (1.33). However, either as a result of misinterpretation, or because of a poor translation from French, almost all textbooks still write that pure hydrogen peroxide is a “thick syrupy liquid”, and even explain this theoretically by the formation of hydrogen bonds. But water also forms hydrogen bonds. In fact, the viscosity of H 2 O 2 is the same as that of slightly cooled (up to about 13 ° C) water, but it cannot be said that cool water is thick, like syrup.
2Н 2 O 2 → 2H 2 O + O 2
However, very pure hydrogen peroxide is stable.
Hydrogen peroxide exhibits very weak acidic properties (K = 1.4 10 -12). Under the action of a concentrated solution of H 2 O 2 on hydroxides, in some cases, metal peroxides (Li 2 O 2, MgO 2, etc.) can be isolated:
H 2 O 2 + 2NaOH → Na 2 O 2 + 2H 2 O
The peroxide group -O-O- is part of many substances. Such substances are called peroxides, or peroxide compounds. These include metal peroxides (Na 2 O 2 , BaO 2 , etc.), which can be considered as salts of hydrogen peroxide. Acids containing a peroxide group are called peroxoacids, for example, peroxomonophosphoric H 3 PO 5 and peroxysulphuric H 2 S 2 O 8 acids.
redox properties
Hydrogen peroxide has strong oxidizing as well as reducing properties. It oxidizes nitrites to nitrates, releases iodine from metal iodides, breaks down unsaturated compounds in situ double bonds. Hydrogen peroxide reduces gold and silver salts, as well as oxygen when reacted with an aqueous solution of potassium permanganate in an acidic environment.
When H 2 O 2 is reduced, H 2 O or OH– is formed, for example: H 2 O 2 + 2KI + H 2 SO 4 \u003d I 2 + K 2 SO 4 + 2H 2 O
Under the action of strong oxidizing agents, H 2 O 2 exhibits reducing properties, releasing free oxygen:
O 2 2– – 2e – → O 2
The reaction of KMnO 4 with H 2 O 2 is used in chemical analysis to determine the content of H 2 O 2:
5H 2 O 2 + 2KMnO 4 + 3H 2 SO 4 → 5O 2 + 2MnSO 4 + K 2 SO 4 + 8H 2 O
Oxidation of organic compounds with hydrogen peroxide (for example, sulfides and thiols) is advisable to carry out in an acetic acid medium.
Biological properties
Hydrogen peroxide belongs to the reactive forms of oxygen and, with increased formation in the cell, causes oxidative stress. Some enzymes, such as glucose oxidase, form hydrogen peroxide during the redox reaction, which can play a protective role as a bactericidal agent. Mammalian cells do not have enzymes that reduce oxygen to hydrogen peroxide. However, several enzyme systems (xanthine oxidase, NAD (P) H-oxidase, cyclooxygenase, etc.) produce superoxide, which spontaneously or under the action of superoxide dismutase is converted into hydrogen peroxide.
Receipt
Hydrogen peroxide is produced industrially by a reaction involving organic substances, in particular, the catalytic oxidation of isopropyl alcohol:
(CH 3) 2 CH (OH) + O 2 → CH 3 C (O)CH 3 + H 2 O 2
A valuable by-product of this reaction is acetone.
In laboratory conditions, to obtain hydrogen peroxide, the reaction is used
BaO 2 + H 2 SO 4 → H 2 O 2 + BaSO 4
Concentration and purification of hydrogen peroxide is carried out by gentle distillation.
Application
3% hydrogen peroxide solution
Due to its strong oxidizing properties, hydrogen peroxide has found wide application in everyday life and in industry, where it is used, for example, as a bleach in textile production and in the manufacture of paper. It is used as rocket fuel - as an oxidizing agent or as a one-component (with decomposition on a catalyst). It is used in analytical chemistry, in medicine, as a foaming agent in the production of porous materials, in the production of disinfectants and bleaching agents. In industry, hydrogen peroxide also finds its use as a catalyst, a hydrogenating agent, and as an epoxidizing agent in the epoxidation of olefins. In medicine, hydrogen peroxide solutions are used as an antiseptic. Upon contact with damaged skin and mucous membranes, hydrogen peroxide decomposes under the influence of the catalase enzyme with the release of oxygen, which promotes blood clotting and creates unfavorable conditions for the development of microorganisms. However, this action is short-lived and has a weak effect. However, hydrogen peroxide (pharmacy name - hydrogen peroxide, 3%) is used in the primary treatment of wounds (including open wounds). Hydrogen peroxide is very effective for minor scratches, especially in children - it doesn't sting, it's odorless, it's colorless. However, it may cause a slight burning sensation in the open wound area. The cost of a vial of such a solution (for 2009) is about 6 rubles. In the food industry, hydrogen peroxide solutions are used to disinfect technological surfaces of equipment that are in direct contact with the product. In addition, at enterprises for the production of dairy products, juices, hydrogen peroxide solutions are used to disinfect packaging (Tetra Pak technology). For technical purposes, hydrogen peroxide is used in the production of electronic equipment.
Release forms
Available in the form of aqueous solutions, the standard concentration is 3, 30, 38, 50, 60, 85, 90 and 98%. A 30% aqueous hydrogen peroxide solution stabilized by the addition of sodium phosphates is called perhydrol.
Danger of use
Despite the fact that hydrogen peroxide is not toxic, its concentrated solutions, when it comes into contact with the skin, mucous membranes and in Airways cause burns. In high concentrations, insufficiently pure hydrogen peroxide can be explosive.
Links
Literature
- Akhmetov N.S. "General and inorganic chemistry" M.: Higher school, 2001
- Karapetyants M.Kh. Drakin S.I. General and inorganic chemistry. M.: Chemistry 1994
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See what "Hydrogen Peroxide" is in other dictionaries:
HYDROGEN PEROXIDE- (Hydrogenium hy peroxy datum, Hydrogenium peroxy datum), H202, syrupy liquid, transparent, colorless in thin layers, blue in thick layers, 1x / 2 times heavier than water, metallic pungent taste, dissolves in any ratio in ... ... Big Medical Encyclopedia
HYDROGEN PEROXIDE- colorless liquid; mixes well with water; used as a disinfectant (for gargling, for small cuts, etc.) and bleaching agent. Used for bleaching cotton, linen, woolen and silk fabrics, feathers and… The Concise Encyclopedia of the Household
- (H2O2), a liquid composed of hydrogen and oxygen, usually sold in aqueous solutions. Peroxide is obtained by electrolytic OXIDATION of sulfuric acid and methods based on the REDUCTION of oxygen. Hydrogen peroxide solution is used ... ... Scientific and technical encyclopedic dictionary
HYDROGEN PEROXIDE, the same as hydrogen peroxide ... Modern Encyclopedia
Same as hydrogen peroxide... Big Encyclopedic Dictionary
Active ingredient ›› Hydrogen peroxide (Hydrogen peroxide) … Medicine Dictionary
Hydrogen peroxide- HYDROGEN PEROXIDE, the same as hydrogen peroxide. … Illustrated Encyclopedic Dictionary
hydrogen peroxide- An inorganic substance that quickly decomposes in the body (under the action of the enzyme catalase) with the formation of molecular oxygen: H2O2. [Arefiev V.A., Lisovenko L.A. English-Russian explanatory dictionary of genetic terms 1995 407s.] Topics ... ... Technical Translator's Handbook
I (technical) has recently been used in fairly wide sizes for bleaching silk and woolen products, as well as feathers. Compared to sulfuric acid, which has long been used for this purpose, hydrogen peroxide bleaches ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron
See Hydrogen peroxide. * * * HYDROGEN PEROXIDE HYDROGEN PEROXIDE, the same as hydrogen peroxide (see HYDROGEN PEROXIDE) ... encyclopedic Dictionary
Hydrogen peroxide (hydrogen peroxide), H 2 O 2 - the simplest representative of peroxides. Colorless liquid with a "metallic" taste, unlimitedly soluble in water, alcohol and ether. Concentrated aqueous solutions are explosive. Hydrogen peroxide is a good solvent. It is released from water in the form of an unstable crystalline hydrate H 2 O 2 2H 2 O.
The structure of the molecule
The H 2 O 2 molecule contains the peroxide anion O 2 -2. Each oxygen atom forms 2 covalent bonds, but has an oxidation state of -1. In a simplified form, the structure of the molecule is reflected by the graphic formula:
H +1 -O -1 -O -1 -H +1
Physical Properties
In pure anhydrous form, H 2 O 2 - colorless. syrupy liquid with a density of 1.45 g / cm 3 (mp. -0.41 ° C, bp 150.2 ° C). It is miscible with water in any ratio, it also dissolves in alcohol, ether. 30% solution of H 2 O 2 is called perhydrol. Like water, H 2 O 2 is a good polar solvent in which substances with ionic and polar covalent bonds dissociate into ions.
Chemical properties
Decomposition of H 2 O 2 (disproportionation)
2H 2 O 2 \u003d 2H 2 O + O 2
2O -1 - 2e - → O 2 0
2O -1 + 2e - → 2O -2
At T > 90°C, hydrogen peroxide decomposes almost completely. The reason for the fragility of H 2 O 2 molecules is the instability of the oxygen atom in the oxidation state -1.
H 2 O 2 - weak acid
H 2 O 2 molecules dissociate to a small extent in an aqueous solution according to the scheme:
H 2 O 2 \u003d H + + HO 2 -
(K diss = 1.5 * 10 -12 at 20°C)
Acidic properties are manifested in reactions with alkalis to form salts - medium (peroxides) and acidic (hydroperoxides), for example:
H 2 O 2 + Ba (OH) 2 \u003d BaO 2 + 2H 2 O barium peroxide
Hydrolysis of metal peroxides
Although peroxides resemble oxides in composition, they actually have the properties of salts. In aqueous solutions, they are completely hydrolyzed with the release of H 2 O 2:
K 2 O 2 + 2H 2 O \u003d 2KOH + H 2 O 2
Obtaining H 2 O 2 from metal peroxides
Since H 2 O 2 is a very weak acid, it is displaced from its salts by both strong and weak acids, for example:
ВаO 2 + H 2 SO 4 \u003d H 2 O 2 + BaSO 4 ↓
BaO 2 + CO 2 + H 2 O \u003d H 2 O 2 + BaCO 3 ↓
H 2 O 2 strong oxidizing agent
Oxygen atoms, which are in an unstable oxidation state -1, tend to acquire one more electron to transition to a stable state. Therefore, hydrogen peroxide exhibits very strong oxidizing properties, especially in an acidic environment:
H 2 O - 2 + 2H + + 2e - → 2H 2 O -2
Oxidation of inorganic substances
ZN 2 O 2 + 2NH 3 \u003d N 2 + 6H 2 O
4H 2 O 2 + H 2 S \u003d H 2 SO 4 + 4H 2 O
H 2 O 2 + 2HI \u003d I 2 + 2H 2 O
4H 2 O 2 + PbS \u003d PbSO 4 + 4H 2 O
ZH 2 O 2 + 2CrCl 3 + 10KOH = 2K 2 CrO 4 + 6KCl + 8H 2 O
H 2 O 2 + 2FeSO 4 + H 2 SO 4 = Fe 2 (SO 4) 3 + 2H 2 O
Oxidation of organic substances
Conc. aqueous solutions of H 2 O 2 mixed with organic substances are capable of ignition and explosion on impact. For example, organic acids are oxidized to CO 2 and H 2 O (as in combustion in O 2):
4H 2 O 2 + CH 3 COOH \u003d 2CO 2 + 6H 2 O
H 2 O 2 + H 2 C 2 O 4 \u003d 2CO 2 + 2H 2 O
alkali peroxides. Me - very strong oxidizing agents
Oxidizes many inorganic and organic matter, for example:
4Na 2 O 2 + CH 3 COOH \u003d 2Na 2 CO 3 + 4NaOH
Na 2 O 2 + SO 2 \u003d Na 2 SO 4
An important reaction is the disproportionation of Na peroxide when interacting with carbon dioxide:
2Na 2 O 2 + 2СO 2 \u003d 2Na 2 CO 3 + O 2
This reaction is based on the use of Na 2 O 2 in self-contained breathing apparatus and in enclosed spaces to absorb CO 2 and form O 2 .
H 2 O 2 - a weak reducing agent (in reactions with very strong oxidizing agents)
The oxidation of hydrogen peroxide usually proceeds according to the scheme:
2Н 2 O - 2 - 2e - → O 0 2 + 2H +
Reaction examples:
5Н 2 O 2 + 2КМnO 4 + 3H 2 SO 4 = 5O 2 + 2MnSO 4 + K 2 SO 4 + 8Н 2 O
ZN 2 O 2 + K 2 Cr 2 O 7 + 4H 2 SO 4 \u003d 3O 2 + Cr 2 (SO 4) 3 + K 2 SO 4 + 7H 2 O
3H 2 O 2 + KClO 3 \u003d 3O 2 + KCl + 3H 2 O
3H 2 O 2 + 2AuCl 3 \u003d 3O 2 + 2Au + 6HCl
It is probably difficult to find a person who has never encountered hydrogen peroxide in his life, because there are small bottles of dark glass in almost every first aid kit. It may seem that hydrogen peroxide is completely harmless and absolutely necessary in every home. But if there are no questions about its necessity, then there are still questions about its absolute harmlessness - this substance, despite its apparent simplicity, still arouses keen interest, and even controversy ...
By the way, I wonder where hydrogen peroxide came from, because in nature there is no substance with the chemical formula H 2 O 2 ... The history of peroxide began almost two hundred years ago, back in 1818, when the Frenchman Louis Tenaro, conducting chemical experiments with various substances, decided combine barium peroxide and sulfuric acid.
It is as a result of this chemical reaction and a substance was obtained that was very similar to ordinary water, but differed from water in that it was one and a half times heavier, evaporated noticeably more slowly and could be dissolved in ordinary water in any proportions. The new substance was named "oxidized water".
Luis Tenero and other chemists became interested in an unstable and easily decaying substance and continued their experiments. Industrial production of a substance with the chemical formula H 2 O 2 began in 1873 in Berlin, but the shelf life of the resulting liquid remained very short and did not exceed two weeks.
Interestingly, during the Second World War, German scientists were able to create a fighter aircraft that could reach speeds of almost a thousand kilometers per hour and run on a substance that was obtained as a result of a chemical reaction of hydrogen peroxide and methanol. In addition, hydrogen peroxide (peroxide) with a concentration of 80% was also used in ballistic missiles ...
So the fate of the most common and long-known hydrogen peroxide turned out to be difficult and rather entertaining. So, hydrogen peroxide: the benefits and harms of this, at first glance, a very simple substance.
The benefits of hydrogen peroxide
Hydrogen peroxide, the chemical formula of which is H 2 O 2 , upon contact with water, it decomposes into components, that is, into water and oxygen, therefore hydrogen peroxide is quite rightly considered an environmentally friendly substance that cannot cause any harm to the environment.
As for the unconditional benefits of hydrogen peroxide, this is, first of all, its use for medical purposes. As you know, according to official recommendations, 3% hydrogen peroxide is used for medical purposes, and the purpose of this remedy is exclusively external - the treatment of minor skin lesions (abrasions, scratches, small wounds), stopping minor bleeding, and also use for rinsing with stomatitis.
What explains the disinfecting effect that hydrogen peroxide has on various skin lesions? The disinfecting (antiseptic) effect is explained by the fact that when hydrogen peroxide comes into contact with the skin, oxygen is released (foam appears), and, as a result, the wound gets the opportunity to be cleaned mechanically - the resulting oxygen foam cleans the wound simply mechanically, washing away microbes, dirt and even necrotic formations that may already have appeared in the wound.
Composition of hydrogen peroxide 3% (Hydrogen peroxide)
However, hydrogen peroxide cannot be considered the only and completely reliable way to clean wounds, since the antibacterial effect of this agent is rather short-lived. In addition, some microorganisms do not react to hydrogen peroxide in any way, because they are resistant to this agent, which is explained by the presence of enzymes that simply destroy peroxide.
Also, some people, including some healthcare professionals, find it helpful to take 3% hydrogen peroxide by mouth. As an explanation, the argument is put forward that any cells of the human body constantly need oxygen, namely, oxygen is released during the breakdown of peroxide.
Opponents of this method of using hydrogen peroxide say that when hydrogen peroxide decomposes, not only molecular oxygen enters the body, but also free radicals that can destroy any protein formations in the body and even destroy the cellular structure.
Researchers report that it is the free radicals that are in the body that can cause the development of very serious diseases, including atherosclerosis, diabetes, and even cancer.
The researchers also warn that free radicals adversely affect cell division, slowing down this process, resulting in earlier aging of the skin, and any wound surfaces, injuries and injuries heal for a longer time.
Treatment of wounds with hydrogen peroxide
Traditionally, small and shallow wound surfaces are treated with a 3% hydrogen peroxide solution. However, the results of some studies claim that this method of wound treatment, although it cleans the wound and also disinfects it, but still slows down healing. That is, the really good cleansing abilities of hydrogen peroxide (peroxide) do not at all have a positive effect on the healing of any wound surfaces, including even ordinary abrasions.
Studies have shown that those concentrations of hydrogen peroxide that can provide an antiseptic (disinfecting) effect can damage cells that are adjacent to the wound, and that is why healing requires more long time. In addition, there is convincing evidence that hydrogen peroxide can lead to the destruction of newly formed skin cells, so wound healing is complicated and slowed down, and scars form on the skin.
But medicine cannot refuse to use hydrogen peroxide for the process of high-quality wound treatment, especially when it comes to complex, deep or any purulent wounds - it is in such cases that hydrogen peroxide (peroxide) remains the drug of first choice, that is, it is hydrogen peroxide that should be preferred over other antiseptics.
This is explained not only by the ability of antiseptic, that is, disinfecting, effects, but also by the fact that as a result of the use of hydrogen peroxide, a significant amount of foam appears due to interaction with peroxidase (enzyme). Namely, the resulting foam softens and allows you to almost painlessly separate pus, blood clots, dead (necrotic) tissue areas from living tissues.
The elements dangerous for the wound, softened and separated from living tissues, are easily washed out of the wound with the help of an antiseptic solution used in a particular case. But it is extremely difficult to remove dead particles and pathological formations from a wound that has not been carefully treated with hydrogen peroxide, which worsens the condition of the wound and the condition of the victim, and also increases the time it takes to heal.
Researchers and clinicians warn that treatment skin and wound surfaces with hydrogen peroxide should be very careful and it is very important not to overdo it, since hydrogen peroxide not only destroys bacteria, but is also capable of destroying living cells of the body, thereby destroying the protective layer formed on the skin. As a result, too much or too much use of hydrogen peroxide, even with the best intentions, makes the skin more sensitive, in addition, the skin becomes vulnerable to harmful microorganisms: microbes, viruses and bacteria.
Attention! With the help of hydrogen peroxide, it is necessary to treat complex (especially purulent) wounds that need thorough cleaning. Simple and shallow wounds do not require hydrogen peroxide treatment - other antiseptic (disinfecting) agents can be used to treat them.
Rinsing with hydrogen peroxide
In addition to other uses for the beneficial properties of hydrogen peroxide, this substance is also used to gargle in case of sore throats of any etiology or pharyngitis in order to reduce pain and speed up the healing process.
It should be noted that for any inflammatory processes that occur in the throat, it is very important that the mucous membrane of the throat receives sufficient moisture and does not dry out, and that various pathogens, including microbes and viruses, are removed from the surface of the mucous membrane in a timely manner, which will significantly speed up recovery.
The disinfecting and cleansing properties of hydrogen peroxide are widely used in various fields of medicine, including ENT practice in the treatment of throat diseases.
Otolaryngologists may recommend hydrogen peroxide for topical use as an antiseptic in the treatment of diseases such as tonsillitis of various etiologies (especially often for the treatment of purulent tonsillitis); pharyngitis, colds, in which the throat is damaged, as well as in the treatment of stomatitis of various etiologies.
All of these diseases are united by one feature - on the mucous membrane of the surface of the throat or on the mucous membrane of the surface of the oral cavity, wounds can form in which purulent contents are collected, as well as a small amount of blood and some substances of a protein nature. IN
while rinsing the throat and mouth with a solution of oxygen peroxide (peroxide), that is, when this chemical comes into contact with damaged surfaces, the reaction of releasing active oxygen begins and foam is formed; as a result of this, the wounds on the mucous membranes of the throat and oral cavity mechanically get rid of purulent contents, blood and blood clots, as well as any protein substances contained in the wound that interfere with wound healing and recovery.
Hydrogen peroxide is very effective if it becomes necessary to remove plaque from the surface of the tonsils in the throat.
Of course, the use of hydrogen peroxide in the treatment of diseases of the throat and oral cavity is reduced only to a mechanical effect on purulent formations and accumulations of pus, which are simply washed out from the surface of the mucosa and removed.
However, it is the mechanical removal of harmful purulent formations that is very important so that the body can more effectively fight any infection, since procedures with hydrogen peroxide reduce the number of infectious agents and can significantly reduce body intoxication and its consequences.
However, when gargling with hydrogen peroxide, some rules should be followed.
In order for hydrogen peroxide to be able to gargle, hydrogen peroxide 3% must be diluted in water. This is necessary, since undiluted peroxide can damage the throat even more, which will require a long and complicated treatment.
To prepare a solution that is safe for the throat, but effective in combating harmful microorganisms, take 100 ml of boiled and chilled water and dissolve a tablespoon (but not more!) In it of ordinary three percent hydrogen peroxide. It is forbidden to use a stronger solution for gargling, because it is dangerous!
Alternatively, hydroperite tablets can be used. To obtain a solution suitable for gargling, one tablet of this substance must be dissolved in boiled and chilled water, which will require 200 ml.
- Rule number 1. You can gargle with a solution of hydrogen peroxide no more than once every three hours. In total, four to five rinses should be carried out during the day.
- Rule number 2 (this is very important!).
After rinsing the throat and mouth with a solution of hydrogen peroxide, it is necessary to immediately rinse (rinse) the throat and mouth with another solution to wash out the foam in which the infectious agents have already dissolved and to completely clear the throat.
Also, additional rinsing neutralizes the effect of hydrogen peroxide on the mucous membranes of the mouth and throat, and they are not damaged.
To carry out additional gargling after procedures using a hydrogen peroxide solution, you can rinse your throat with a solution of soda, herbal decoction (use chamomile, sage and other herbs for its preparation); a weak solution (barely pink) of potassium permanganate (potassium permanganate); sea water (water with dissolved sea salt) or even with ordinary boiled and cooled water.
Rinses with hydrogen peroxide should be carried out until the tonsils are cleared of plaque, that is, until the formation of purulent contents stops.
In addition to rinsing with a solution of hydrogen peroxide, with tonsillitis and other infectious diseases throat sometimes the doctor prescribes lubrication of the tonsils with a solution of hydrogen peroxide, however, a more concentrated solution of the drug is used to lubricate the tonsils.
It is also easy to prepare a concentrated solution of a hydrogen peroxide preparation for lubricating certain parts of the throat (in particular, the tonsils). To do this, three tablespoons of three percent hydrogen peroxide should be dissolved in 100 ml of warm boiled water. The resulting solution should be lubricated with inflamed tonsils using special cotton swabs. In addition, the same solution can be applied to sore tonsils by blotting them with cotton swabs, which were previously moistened in the prepared solution.
Attention! Hydrogen peroxide is a very strong oxidizing agent, and even the use of solutions requires extra care. If gargling is carried out using a solution of hydrogen peroxide, then it should be remembered that in no case should this solution be swallowed. For young children, gargling with hydrogen peroxide is completely unacceptable!
The use of hydrogen peroxide solutions for the treatment of throat is completely unacceptable if it is known about the individual intolerance to this drug or an allergic reaction to the drug is possible.
With regard to adverse reactions, such as burning or any damage to the mucous membrane of the throat due to the use of gargles with hydrogen peroxide, such adverse reactions are completely excluded if the solutions are prepared correctly (that is, no more peroxide is used than necessary), and also if the procedure is performed no more often than prescribed by the attending physician.
The use of peroxide in industry and at home
Of course, such a unique oxidizing agent as hydrogen peroxide is used in a wide variety of industries and in the most different areas Everyday life.
The main scope of hydrogen peroxide is the bleaching of various materials, and not at all medicine, where an extremely small part of this drug is used.
Why does the industry prefer to use hydrogen peroxide for bleaching procedures? The fact is that this oxidizing agent has a very mild effect and does not have any harmful effect directly on the material that is being bleached, that is, it does not damage its structure.
One more important feature hydrogen peroxide when used in industrial processes is that the use of hydrogen peroxide for bleaching does not cause any harm to environment, that is, the use of this substance is not capable of worsening ecological situation. After all, whitening, in fact, is carried out with the help of oxygen, so no air pollution, no pollution water resources are simply impossible. That is why many industries, including pulp mills, have abandoned the bleaching of their products with chlorine, which was used for this purpose before.
It has also been repeatedly noted that even at home, bleaching with chlorine is highly undesirable, since it is unsafe for health, destroys tissues, and the effect is far from ideal. Recently, however, a lot of oxygen-based laundry detergents have appeared, in which the same hydrogen peroxide works. Such washing is much more efficient, safer, fabrics last longer, and there is no unpleasant smell, as with bleaching with chlorine, at all.
Any woman knows another way to use hydrogen peroxide - lightening hair. And although the industry offers a considerable amount of a wide variety of hair dyes, hydrogen peroxide (hydroperite) remains a very popular remedy, especially given not only its effectiveness, but also its low cost.
A very important area of application for hydrogen peroxide is industry, where solutions of hydrogen peroxide in very high concentrations (more than 80%) are used as an energy source and even as an oxidizer for jet fuel.
The chemical industry uses hydrogen peroxide in the production of polymeric materials, including some porous substances.
Hydrogen peroxide has also found application in the wine industry, where it is successfully used for the rapid artificial aging of wines.
An important area of application of hydrogen peroxide is the textile industry and the pulp and paper industry, where fabrics and paper are bleached with peroxide.
As for the use of hydrogen peroxide in everyday life, this substance is known as a very effective cleaning agent. Hydrogen peroxide can be used to clean plumbing sinks, pipe surfaces, and even furniture surfaces.
Many housewives use hydrogen peroxide as a well-proven floor cleaner - for this, in four liters hot water about a third or a quarter of a glass (100-150 g) of peroxide should be dissolved.
Attention! When using hydrogen peroxide in everyday life, one should not forget that this substance is about one and a half times heavier than water.
If fungus and mold have appeared in the dwelling, then you can also fight them with the help of the same peroxide. To get a positive result, it is necessary to pour two parts of water and one part of peroxide (by volume) into a household sprayer and spray the mixture onto a fungus-infected surface. After ten minutes, the surface must be thoroughly cleaned.
In the kitchen, hydrogen peroxide also does not remain without work. This substance has proven itself when washing dishes. To do this, add about 100 g of peroxide to the sink with water and then wash the dishes as usual.
It is very useful to treat cutting boards with hydrogen peroxide, especially for fish and meat - this treatment will destroy all dangerous microorganisms, viruses and bacteria on the boards, including salmonella, which is very dangerous to health.
It is recommended to use hydrogen peroxide to clean plumbing, especially toilets. In order for the toilet to become really clean, you should mix hydrogen peroxide and clean water in equal proportions and spray the resulting mixture onto the surface of the toilet bowl, after which everything should be washed off with water. Any microbes do not withstand contact with hydrogen peroxide, that is, with ordinary peroxide.
Hydrogen peroxide can be useful for maintaining the necessary cleanliness and for disinfecting a toothbrush, on the surface of which a wide variety of pathogenic microbes can accumulate. To get rid of unwanted microorganisms, it is useful to hold the toothbrush from time to time in a three percent hydrogen peroxide solution (for no more than two minutes), and then rinse thoroughly with running water.
Hydrogen peroxide will also come in handy in the kitchen to keep certain foods longer. To do this, hydrogen peroxide should be mixed with water in equal proportions and fruits and vegetables should be sprayed from the sprayer, which should then be thoroughly washed in running water. Products processed in this way will be stored for a longer time.
To keep the kitchen sponge clean, it should also be dipped in the same (1:1) hydrogen peroxide solution. Then the sponge should be thoroughly rinsed and dried, and only then continue to use.
Attention! Experts categorically do not recommend using hydrogen peroxide for teeth whitening, since the whitening effect is based on oxidative processes, which inevitably lead to the destruction of tissues, including tooth tissues.
Hydrogen peroxide is widely used in the food industry, as it allows you to effectively and safely disinfect equipment (its technological surfaces). In the production of fruit and vegetable juices and dairy products, which are packed in Tetra Pak cardboard bags, hydrogen peroxide is used as a disinfectant.
Interesting! In the aquarium trade, a three percent solution of hydrogen peroxide (peroxide) is used to clean aquariums of unwanted microorganisms and even to resuscitate aquarium fish suffocated from lack of oxygen.
Hydrogen peroxide in the country
As for the use of hydrogen peroxide in summer cottages, then, of course, this remedy is necessary for the treatment of injuries received, which are very likely in the country.
But the use of this tool in summer conditions is not limited to medical purposes.
Experienced gardeners and amateur gardeners claim that watering plants with a weak solution of hydrogen peroxide improves the growth and condition of any plant.
To prepare a solution for irrigation, 25 g of a three percent solution of hydrogen peroxide should be dissolved in a liter of clean water. The resulting product can be used not only for watering plants, but also for spraying trees and bushes - thus, many diseases of garden and garden plants can be avoided.
Also, experienced gardeners advise soaking seeds in a solution of hydrogen peroxide before planting - for the fastest germination. To prepare the solution necessary for soaking the seeds, mix 25 g of three percent peroxide with 500 ml of water. Soak the seeds should not be long - no more than three hours.
Attention! When preparing solutions for gardening, it should be remembered that hydrogen peroxide is one and a half times heavier than water, so 25 g of peroxide is not 25 ml, as is the case with water, but only about 16 ml.
Some gardeners claim that hydrogen peroxide also helps the sick garden trees. In order for the trees to feel better, it is necessary to prepare the so-called peroxide water, for which one part of hydrogen peroxide should be mixed with 32 parts of water, and then unhealthy trees should be sprayed with this mixture.
Another way to apply hydrogen peroxide on suburban area- preparation of animal feed. It's not a secret for anyone that the tops of various plants, straw, or some other waste remain on personal plots. It’s a pity to throw it all away, and not everyone equips compost pits. But turning these varied leftovers into nutritious pet food isn't all that difficult. To do this, for example, soak straw or tops in a solution of hydrogen peroxide. A few hours in this solution makes the food much more attractive to pets, as it becomes more nutritious and is much easier to digest.
The harm of hydrogen peroxide
When people enthusiastically use beneficial features peroxides, it is often forgotten that this substance can be not only useful, but also dangerous, since it is a very strong oxidizing agent. It does not hurt to pay attention to the proportion in which even a three percent peroxide solution should be diluted, which means that this substance is not so safe.
Of course, if hydrogen peroxide is used only for treating wound surfaces, then no special problems are foreseen. The main thing here is not to overdo it and not treat the wound too actively or too often.
However, many people believe that the body simply needs to take hydrogen peroxide inside and that it is this simple remedy that can become a real panacea for all diseases, since the blood can thus receive additional oxygen. Is it really? It should not be forgotten that hydrogen peroxide is a powerful oxidizing agent and that even for external use it is used in very strong dilution. Moreover, even externally, hydrogen peroxide is used only to stop the blood and clean the wound - the oxidizing properties of peroxide do not allow this agent to accelerate the healing of any wounds, but this remedy can slow down the healing process, if used thoughtlessly.
As for taking hydrogen peroxide orally, we should not forget that taking this substance can cause very negative phenomena, including vomiting or just nausea, skin rashes and other allergic reactions, and sleep disturbances, and other neurological symptoms.
Concentrated solutions of hydrogen peroxide (hydrogen peroxide) are very dangerous - when they get on the skin or mucous membranes, they cause burns, and sometimes quite serious ones (3% hydrogen peroxide is most often sold in pharmacies). Among other things, it does not hurt to keep in mind that hydrogen peroxide in its pure form (the so-called pure hydrogen peroxide) is an explosive substance capable of simultaneously releasing large amounts of free oxygen.
Doctors warn against trying to ingest concentrated solutions of hydrogen peroxide, since their action resembles the action of alkalis and can lead to serious destructive (destructive) changes in the body, including death. A lethal dose is the amount of 50 to 100 ml of a thirty percent solution of hydrogen peroxide (perhydrol, hydrogen peroxide) that has entered the body (esophagus, gastrointestinal tract).
What does hydrogen peroxide treat?
Excellent report by Professor of Medicine Neumyvakin I.P. about what hydrogen peroxide treats. We look:
conclusions
Open in the distance In 1818, by the French chemist Louis Tenaro, hydrogen peroxide today has become something ordinary and familiar. Abrasion? Running for peroxide? A cut, a bite, or some other wound?
Peroxide is first called to help, and only then other options for salvation are sought. And in the country, and in the office aquarium, and when cleaning the house, hydrogen peroxide is indispensable. But we must not forget that this substance familiar from childhood is not so harmless and harmless, like any chemical product, like any medicinal product. Peroxide is so easy...
But at the same time, we should not forget that peroxide is very difficult and even sometimes deadly. And it is in this case that the expression of the famous medieval physician Paracelsus, who argued that medicine and poison differ only in dose, is very appropriate. What to add here? Is it that, in addition to the dose, in the case of peroxide, the method of application is no less important.
HYDROGEN PEROXIDE- (the old name is hydrogen peroxide), a compound of hydrogen and oxygen H 2 O 2, containing a record amount of oxygen - 94% by weight. H 2 O 2 molecules contain peroxide groups –О–О– ( cm. PEROXIDES), which largely determine the properties of this compound.
For the first time, hydrogen peroxide was obtained in 1818 by the French chemist Louis Jacques Tenard (1777 - 1857), acting on barium peroxide with highly chilled hydrochloric acid:
BaO 2 + 2HCl BaCl 2 + H 2 O 2. Barium peroxide, in turn, was obtained by burning metallic barium. To isolate H 2 O 2 from the solution, Tenar removed the formed barium chloride from it: BaCl 2 + Ag 2 SO 4 2AgCl + BaSO 4. In order not to use expensive silver salt in the future, sulfuric acid was used to obtain H 2 O 2: BaO 2 + H 2 SO 4 BaSO 4 + H 2 O 2, since barium sulfate remains in the precipitate. Sometimes another method was used: carbon dioxide was passed into a suspension of BaO 2 in water: BaO 2 + H 2 O + CO 2 BaCO 3 + H 2 O 2, since barium carbonate is also insoluble. This method was proposed by the French chemist Antoine Jérôme Balard (1802–1876), who became famous for the discovery of the new chemical element bromine (1826). More exotic methods were also used, for example, the action of an electric discharge on a mixture of 97% oxygen and 3% hydrogen at liquid air temperature (about –190 ° C), so an 87% solution of H 2 O 2 was obtained.
H 2 O 2 was concentrated by carefully evaporating very pure solutions in a water bath at a temperature not exceeding 70–75°C; so you can get about 50% solution. It is impossible to heat up more strongly - H 2 O 2 decomposes, therefore, the distillation of water was carried out at reduced pressure, using a strong difference in vapor pressure (and, consequently, in the boiling point) of H 2 O and H 2 O 2. So, at a pressure of 15 mm Hg. first, mostly water is distilled off, and at 28 mm Hg. and a temperature of 69.7 ° C, pure hydrogen peroxide is distilled off. Another method of concentration is freezing, since when weak solutions freeze, ice contains almost no H 2 O 2. Finally, it can be dehydrated by absorbing water vapor with sulfuric acid in the cold under a glass bell.
Many researchers of the 19th century, who received pure hydrogen peroxide, noted the danger of this compound. So, when they tried to separate H 2 O 2 from water by extraction from dilute solutions with diethyl ether, followed by distillation of the volatile ether, the resulting substance sometimes exploded for no apparent reason. In one of these experiments, the German chemist Yu.V. Brühl obtained anhydrous H 2 O 2 , which had the smell of ozone and exploded at the touch of an unmelted glass rod. Despite the small amounts of H 2 O 2 (only 1–2 ml), the explosion was so strong that it punched a round hole in the table board, destroyed the contents of its box, as well as flasks and devices standing on the table and nearby.
physical properties. Pure hydrogen peroxide is very different from the familiar 3% solution of H 2 O 2 that is in the home first aid kit. First of all, it is almost one and a half times heavier than water (density at 20 ° C is 1.45 g / cm 3). H 2 O 2 freezes at a temperature slightly lower than the freezing point of water - at minus 0.41 ° C, but if you quickly cool a clean liquid, it usually does not freeze, but supercools, turning into a transparent glassy mass. H 2 O 2 solutions freeze at a much lower temperature: a 30% solution at minus 30 ° C, and a 60% solution at minus 53 ° C. H 2 O 2 boils at a temperature higher than ordinary water, - at 150.2 ° C. It wets glass with H 2 O 2 worse than water, and this leads to an interesting phenomenon in the slow distillation of aqueous solutions: while water is distilled from the solution, it, as usual, enters from the refrigerator into the receiver in the form of drops ; when H 2 O 2 begins to distill, the liquid leaves the refrigerator in the form of a continuous thin stream. On the skin, pure hydrogen peroxide and its concentrated solutions leave white spots and cause a sensation of burning pain due to a severe chemical burn.
In an article on the production of hydrogen peroxide, Tenar did not very well compare this substance with syrup, perhaps he meant that pure H 2 O 2, like sugar syrup, strongly refracts light. Indeed, the refractive index of anhydrous H 2 O 2 (1.41) is much greater than that of water (1.33). However, either as a result of misinterpretation, or because of a poor translation from French, almost all textbooks still write that pure hydrogen peroxide is a “thick syrupy liquid”, and even explain this theoretically by the formation of hydrogen bonds. But water also forms hydrogen bonds. In fact, the viscosity of H 2 O 2 is the same as that of slightly cooled (up to about 13 ° C) water, but it cannot be said that cool water is thick, like syrup.
decomposition reaction. Pure hydrogen peroxide is a very dangerous substance, since under certain conditions its explosive decomposition is possible: H 2 O 2 H 2 O + 1/2 O 2 with the release of 98 kJ per mole H 2 O 2 (34 g). This is a very large energy: it is more than that which is released during the formation of 1 mole of HCl in the explosion of a mixture of hydrogen and chlorine; it is enough to completely evaporate 2.5 times more water than is formed in this reaction. Dangerous and concentrated aqueous solutions of H 2 O 2, in their presence, many organic compounds easily ignite spontaneously, and upon impact, such mixtures can explode. To store concentrated solutions, vessels made of extra pure aluminum or waxed glass vessels are used.
More often you have to meet with a less concentrated 30% solution of H 2 O 2, which is called perhydrol, but such a solution is also dangerous: it causes burns on the skin (during its action, the skin immediately turns white due to discoloration of coloring substances), if impurities enter, it is possible explosive eruption. The decomposition of H 2 O 2 and its solutions, including explosive ones, is caused by many substances, for example, heavy metal ions, which in this case play the role of a catalyst, and even dust particles.
H 2 O 2 explosions are explained by the strong exothermicity of the reaction, the chain nature of the process, and a significant decrease in the activation energy of H 2 O 2 decomposition in the presence of various substances, as can be judged from the following data:
The enzyme catalase is found in the blood; it is thanks to her that the pharmaceutical “hydrogen peroxide” “boils” from the release of oxygen when it is used to disinfect a cut finger. The reaction of decomposition of a concentrated solution of H 2 O 2 under the action of catalase is used not only by a person; it is this reaction that helps the bombardier beetle fight enemies by releasing a hot jet at them ( cm. EXPLOSIVES). Another enzyme, peroxidase, acts differently: it does not decompose H 2 O 2, but in its presence other substances are oxidized with hydrogen peroxide.
Enzymes that affect the reactions of hydrogen peroxide play an important role in the life of the cell. Energy is supplied to the body by oxidation reactions with the participation of oxygen coming from the lungs. In these reactions, H 2 O 2 is intermediately formed, which is harmful to the cell, as it causes irreversible damage to various biomolecules. Catalase and peroxidase together convert H 2 O 2 into water and oxygen.
The decomposition reaction of H 2 O 2 often proceeds according to the radical chain mechanism ( cm. CHAIN REACTIONS), while the role of the catalyst is to initiate free radicals. So, in a mixture of aqueous solutions of H 2 O 2 and Fe 2+ (the so-called Fenton's reagent), an electron transfer reaction occurs from the Fe 2+ ion to the H 2 O 2 molecule with the formation of the Fe 3+ ion and a very unstable radical anion . - , which immediately decomposes into the OH anion - and the free hydroxyl radical OH . (cm. FREE RADICALS). Radical OH . very active. If there are organic compounds in the system, then their various reactions with hydroxyl radicals are possible. So, aromatic compounds and hydroxy acids are oxidized (benzene, for example, turns into phenol), unsaturated compounds can attach hydroxyl groups to the double bond: CH 2 \u003d CH–CH 2 OH + 2OH . NOCH 2 -CH (OH) -CH 2 -OH, and can enter into a polymerization reaction. In the absence of suitable reagents, OH . reacts with H 2 O 2 to form a less active radical HO 2 . , which is able to reduce Fe 2+ ions, which closes the catalytic cycle:
H 2 O 2 + Fe 2+ Fe 3+ + OH . +OH-
IS HE . + H 2 O 2 H 2 O + HO 2 .
HO2 . + Fe 3+ Fe 2+ + O 2 + H +
H + + OH - H 2 O.
Under certain conditions, a chain decomposition of H 2 O 2 is possible, the simplified mechanism of which can be represented by the scheme
IS HE . + H 2 O 2 H 2 O + HO 2 . 2 . + H 2 O 2 H 2 O + O 2 + OH . etc.
The decomposition reactions of H 2 O 2 proceed in the presence of various metals of variable valence. Bound into complex compounds, they often greatly enhance their activity. For example, copper ions are less active than iron ions, but bound in ammonia complexes 2+, they cause rapid decomposition of H 2 O 2 . A similar effect is exerted by Mn 2+ ions bound into complexes with some organic compounds. In the presence of these ions, it was possible to measure the length of the reaction chain. To do this, the reaction rate was first measured by the rate of oxygen evolution from the solution. Then, an inhibitor, a substance that efficiently reacts with free radicals and thus terminates the chain, was introduced into the solution at a very low concentration (about 10–5 mol/l). The release of oxygen immediately stopped, but after about 10 minutes, when all the inhibitor was used up, it resumed again at the same rate. Knowing the rate of reaction and the rate of chain termination, it is easy to calculate the chain length, which turned out to be 10 3 links. The large chain length determines the high efficiency of H 2 O 2 decomposition in the presence of the most efficient catalysts, which generate free radicals at a high rate. With the indicated chain length, the rate of decomposition of H 2 O 2 actually increases by a factor of a thousand.
Sometimes a noticeable decomposition of H 2 O 2 is caused even by traces of impurities, which are almost not detected analytically. For example, one of the most effective catalysts turned out to be a metal osmium sol: its strong catalytic effect was observed even at a dilution of 1:10 9 , i.e. 1 g Os per 1000 tons of water. Active catalysts are colloidal solutions of palladium, platinum, iridium, gold, silver, as well as solid oxides of some metals - MnO 2 , Co 2 O 3 , PbO 2 and others, which do not change themselves. Decomposition can go very rapidly. So, if a small pinch of MnO 2 is thrown into a test tube with a 30% solution of H 2 O 2, a vapor column escapes from the test tube with splashes of liquid. With more concentrated solutions, an explosion occurs. The decomposition proceeds more smoothly on the platinum surface. In this case, the state of the surface has a strong influence on the reaction rate. The German chemist Walter Spring conducted at the end of the 19th century. such an experience. In a carefully cleaned and polished platinum cup, the decomposition of a 38% solution of H 2 O 2 did not proceed even when heated to 60 ° C. If, however, a barely noticeable scratch is made on the bottom of the cup with a needle, then the already cold (at 12 ° C) solution begins emit oxygen bubbles at the site of the scratch, and when heated, decomposition along this site noticeably increases. If spongy platinum, which has a very large surface, is introduced into such a solution, explosive decomposition is possible.
The rapid decomposition of H 2 O 2 can be used for a spectacular lecture experience if a surfactant (soap, shampoo) is added to the solution before the catalyst is added. The released oxygen creates a rich white foam, which has been called "elephant toothpaste".
H 2 O 2 + 2I - + 2H + 2H 2 O + I 2
I 2 + H 2 O 2 2I - + 2H + + O 2.
A non-chain reaction also occurs in the case of oxidation of Fe 2+ ions in acidic solutions: 2FeSO 4 + H 2 O 2 + H 2 SO 4 Fe 2 (SO 4) 3 + 2H 2 O.
Since aqueous solutions almost always contain traces of various catalysts (decomposition can also be catalyzed by metal ions contained in glass), inhibitors and stabilizers that bind metal ions are added to H 2 O 2 solutions, even diluted ones, during their long-term storage. In this case, the solutions are slightly acidified, since under the action of pure water on glass, a weakly alkaline solution is obtained, which contributes to the decomposition of H 2 O 2.
All these features of H 2 O 2 decomposition make it possible to resolve the contradiction. To obtain pure H 2 O 2, it is necessary to carry out distillation under reduced pressure, since the substance decomposes when heated above 70 ° C and even, although very slowly, at room temperature (as stated in the Chemical Encyclopedia, at a rate of 0.5% per year). In this case, how was the boiling point at atmospheric pressure, which appears in the same encyclopedia, equal to 150.2 ° C, obtained? Usually, in such cases, a physicochemical regularity is used: the logarithm of the vapor pressure of a liquid depends linearly on the reciprocal temperature (on the Kelvin scale), so if you accurately measure the vapor pressure of H 2 O 2 at several (low) temperatures, you can easily calculate at what temperature this pressure will reach 760 mm Hg. And this is the boiling point under normal conditions.
Theoretically, OH radicals . can also be formed in the absence of initiators, as a result of breaking the weaker O–O bond, but this requires quite heat. Despite the relatively low breaking energy of this bond in the H 2 O 2 molecule (it is equal to 214 kJ / mol, which is 2.3 times less than for the H–OH bond in the water molecule), the O–O bond is still quite strong, so that hydrogen peroxide is absolutely stable at room temperature. And even at the boiling point (150°C), it must decompose very slowly. The calculation shows that at this temperature, decomposition by 0.5% should also occur quite slowly, even if the chain length is 1000 links. The discrepancy between calculations and experimental data is explained by catalytic decomposition caused by both the smallest impurities in the liquid and the walls of the reaction vessel. Therefore, the activation energy of H 2 O 2 decomposition measured by many authors is always significantly less than 214 kJ/mol even "in the absence of a catalyst". In fact, there is always a decomposition catalyst - both in the form of negligible impurities in the solution, and in the form of vessel walls, which is why heating anhydrous H 2 O 2 to boiling at atmospheric pressure repeatedly caused explosions.
Under certain conditions, the decomposition of H 2 O 2 occurs very unusually, for example, if you heat a solution of H 2 O 2 acidified with sulfuric acid in the presence of potassium iodate KIO 3, then at certain concentrations of reagents, an oscillatory reaction is observed, while oxygen evolution periodically stops, and then resumes with a period of 40 to 800 seconds.
Chemical properties H 2 ABOUT 2 . Hydrogen peroxide is an acid, but a very weak one. The dissociation constant of H 2 O 2 H + + HO 2 - at 25 ° C is 2.4 10 -12, which is 5 orders of magnitude less than for H 2 S. Average H 2 O 2 salts of alkali and alkaline earth metals are usually called peroxides ( cm. PEROXIDES). When dissolved in water, they are almost completely hydrolyzed: Na 2 O 2 + 2H 2 O 2NaOH + H 2 O 2. Hydrolysis is promoted by acidification of solutions. As an acid, H 2 O 2 also forms acid salts, for example, Ba (HO 2) 2, NaHO 2, etc. Acid salts are less susceptible to hydrolysis, but easily decompose when heated with oxygen evolution: 2NaHO 2 2NaOH + O 2. The liberated alkali, as in the case of H 2 O 2, contributes to decomposition.
H 2 O 2 solutions, especially concentrated ones, have a strong oxidizing effect. So, under the action of a 65% solution of H 2 O 2 on paper, sawdust and other combustible substances, they ignite. Less concentrated solutions decolorize many organic compounds, such as indigo. Formaldehyde is oxidized unusually: H 2 O 2 is reduced not to water (as usual), but to free hydrogen: 2HCHO + H 2 O 2 2HCOOH + H 2. If we take a 30% solution of H 2 O 2 and a 40% solution of HCHO, then after a slight heating, a violent reaction begins, the liquid boils and foams. The oxidizing effect of dilute solutions of H 2 O 2 is most pronounced in an acidic environment, for example, H 2 O 2 + H 2 C 2 O 4 2H 2 O + 2CO 2, but oxidation is also possible in an alkaline environment:
Na + H 2 O 2 + NaOH Na 2; 2K 3 + 3H 2 O 2 2KCrO 4 + 2KOH + 8H 2 O.
Oxidation of black lead sulfide to white sulfate PbS + 4H 2 O 2 PbSO 4 + 4H 2 O can be used to restore darkened white lead in old paintings. Under the action of light, hydrochloric acid is also oxidized:
H 2 O 2 + 2HCl 2H 2 O + Cl 2. The addition of H 2 O 2 to acids greatly increases their effect on metals. So, in a mixture of H 2 O 2 and dilute H 2 SO 4 copper, silver and mercury dissolve; iodine in an acidic environment is oxidized to iodic acid HIO 3, sulfur dioxide - to sulfuric acid, etc.
Unusually, the potassium-sodium salt of tartaric acid (Rochelle salt) is oxidized in the presence of cobalt chloride as a catalyst. During the reaction KOOC (CHOH) 2 COONa + 5H 2 O 2 KHCO 3 + NaHCO 3 + 6H 2 O + 2CO 2 pink CoCl 2 changes color to green due to the formation of a complex compound with tartrate - anion of tartaric acid. As the reaction proceeds and the tartrate is oxidized, the complex is destroyed and the catalyst turns pink again. If copper sulphate is used instead of cobalt chloride as a catalyst, then the intermediate compound, depending on the ratio of the initial reagents, will be colored orange or green. After the end of the reaction, the blue color of copper sulphate is restored.
Hydrogen peroxide reacts completely differently in the presence of strong oxidizing agents, as well as substances that readily give off oxygen. In such cases, H 2 O 2 can also act as a reducing agent with simultaneous release of oxygen (the so-called reductive decomposition of H 2 O 2), for example:
2KMnO 4 + 5H 2 O 2 + 3H 2 SO 4 K 2 SO 4 + 2MnSO 4 + 5O 2 + 8H 2 O;
Ag 2 O + H 2 O 2 2Ag + H 2 O + O 2;
O 3 + H 2 O 2 H 2 O + 2O 2;
NaOCl + H 2 O 2 NaCl + H 2 O + O 2.
The latter reaction is interesting in that it produces excited oxygen molecules that emit orange fluorescence ( cm. CHLORINE ACTIVE). Similarly, metallic gold is isolated from solutions of gold salts, metallic mercury is obtained from mercury oxide, etc. Such an unusual property of H 2 O 2 makes it possible, for example, to carry out the oxidation of potassium hexacyanoferrate(II), and then, by changing the conditions, to restore the reaction product to the starting compound using the same reagent. The first reaction takes place in an acidic environment, the second - in an alkaline:
2K 4 + H 2 O 2 + H 2 SO 4 2K 3 + K 2 SO 4 + 2H 2 O;
2K 3 + H 2 O 2 + 2KOH 2K 4 + 2H 2 O + O 2.
(“The dual nature” of H 2 O 2 allowed one teacher of chemistry to compare hydrogen peroxide with the hero of the story of the famous English writer Stevenson The Strange Case of Dr. Jekyll and Mr. Hyde, under the influence of the composition invented by him, he could drastically change his character, turning from a respectable gentleman into a bloodthirsty maniac.)
Getting H 2 ABOUT 2 . H 2 O 2 molecules are always obtained in small quantities during combustion and oxidation of various compounds. During combustion, H 2 O 2 is formed either when hydrogen atoms are abstracted from the starting compounds by intermediate hydroperoxide radicals, for example: HO 2 . + CH 4 H 2 O 2 + CH 3 . , or as a result of recombination of active free radicals: 2OH . H 2 O 2, H . + NO 2 . H 2 O 2. For example, if an oxygen-hydrogen flame is directed to a piece of ice, then the melted water will contain significant amounts of H 2 O 2 formed as a result of the recombination of free radicals (in the flame, H 2 O 2 molecules immediately decay). A similar result is obtained with the combustion of other gases. The formation of H 2 O 2 can also occur at low temperatures as a result of various redox processes.
In industry, hydrogen peroxide has not been obtained for a long time by the Tenar method - from barium peroxide, but more modern methods are used. One of them is the electrolysis of sulfuric acid solutions. At the same time, sulfate ions are oxidized at the anode to oversulfate ions: 2SO 4 2– – 2e S 2 O 8 2– . Persulfuric acid is then hydrolyzed:
H 2 S 2 O 8 + 2H 2 O H 2 O 2 + 2H 2 SO 4.
At the cathode, as usual, hydrogen is released, so that the overall reaction is described by the equation 2H 2 O H 2 O 2 + H 2 . But the main modern way(over 80% of world production) - the oxidation of some organic compounds, for example, ethylanthrahydroquinone, with atmospheric oxygen in an organic solvent, while H 2 O 2 and the corresponding anthraquinone are formed from anthrahydroquinone, which is then again reduced with hydrogen on a catalyst to anthrahydroquinone. Hydrogen peroxide is removed from the mixture with water and concentrated by distillation. A similar reaction also occurs when using isopropyl alcohol (it goes with the intermediate formation of hydroperoxide): (CH 3) 2 CHOH + O 2 (CH 3) 2 C (OOH) OH (CH 3) 2 CO + H 2 O 2. If necessary, the resulting acetone can also be reduced to isopropyl alcohol.
Application H 2 ABOUT 2 . Hydrogen peroxide is widely used, and its world production amounts to hundreds of thousands of tons per year. It is used to obtain inorganic peroxides, as an oxidizer for rocket fuels, in organic synthesis, for bleaching oils, fats, fabrics, paper, for cleaning semiconductor materials, for extracting valuable metals from ores (for example, uranium by converting its insoluble form into a soluble one), for neutralization Wastewater. In medicine, H 2 O 2 solutions are used for rinsing and lubricating in inflammatory diseases of the mucous membranes (stomatitis, tonsillitis), and for the treatment of purulent wounds. In contact lens cases, a very small amount of platinum catalyst is sometimes placed in the lid. Lenses for their disinfection are poured into a pencil case with a 3% solution of H 2 O 2, but since this solution is harmful to the eyes, the pencil case is turned over after a while. At the same time, the catalyst in the lid quickly decomposes H 2 O 2 into pure water and oxygen.
Once it was fashionable to bleach hair with “peroxide”, now there are safer formulations for hair coloring.
In the presence of some salts, hydrogen peroxide forms a kind of solid "concentrate", which is more convenient to transport and use. So, if H 2 O 2 is added to a strongly cooled saturated solution of sodium borate (borax) in the presence, large transparent crystals of sodium peroxoborate Na 2 [(BO 2) 2 (OH) 4] are gradually formed. This substance is widely used for bleaching fabrics and as a component of detergents. H 2 O 2 molecules, like water molecules, are able to penetrate into the crystal structure of salts, forming a kind of crystalline hydrates - peroxohydrates, for example, K 2 CO 3 3H 2 O 2, Na 2 CO 3 1.5H 2 O; the latter compound is commonly known as "persol". The so-called "hydroperite" CO (NH 2) 2 H 2 O 2 is a clathrate - a compound of the inclusion of H 2 O 2 molecules in the voids of the urea crystal lattice.
In analytical chemistry, certain metals can be determined using hydrogen peroxide. For example, if hydrogen peroxide is added to a solution of a titanium (IV) salt - titanyl sulfate, the solution becomes bright orange due to the formation of pertitanic acid:
TiOSO 4 + H 2 SO 4 + H 2 O 2 H 2 + H 2 O. The colorless molybdate ion MoO 4 2– is oxidized by H 2 O 2 into an intensely orange peroxide anion. An acidified solution of potassium dichromate in the presence of H 2 O 2 forms perchromic acid: K 2 Cr 2 O 7 + H 2 SO 4 + 5H 2 O 2 H 2 Cr 2 O 12 + K 2 SO 4 + 5H 2 O, which is quite fast decomposes: H 2 Cr 2 O 12 + 3H 2 SO 4 Cr 2 (SO 4) 3 + 4H 2 O + 4O 2. If you add these two equations, you get the reaction for the reduction of potassium dichromate with hydrogen peroxide:
K 2 Cr 2 O 7 + 4H 2 SO 4 + 5H 2 O 2 Cr 2 (SO 4) 3 + K 2 SO 4 + 9H 2 O + 4O 2.
Perchromic acid can be extracted from an aqueous solution with ether (it is much more stable in an ether solution than in water). The ethereal layer is colored in an intense blue color.
Ilya Leenson
LITERATURE
Dolgoplosk B.A., Tinyakova E.I. Free radical generation and reactions. M., Chemistry, 1982 Chemistry and technology of hydrogen peroxide. L., Chemistry, 1984
Hydrogen peroxide (formula H 2 O 2) is the simplest representative of peroxides. Most often this substance is called hydrogen peroxide.
Properties
It is a colorless liquid with a metallic taste, which is soluble in water, alcohol and ether in any ratio. Aqueous solutions peroxide are explosive: for example, if sodium iodide is lowered into it, then such a reaction will occur (photo on the left).
It is also a good solvent, forming an unstable crystalline hydrate when it is isolated from water. Hydrogen peroxide can serve as both an oxidizing agent and a reducing agent, since all the oxygen atoms in it have an intermediate oxidation state of -1. An example of the demonstration of its oxidizing properties is the reaction with sodium sulfite. The products of this reaction will be sodium sulfate (sulfate) and water. If strong oxidizing agents interact with this peroxide, then in such a reaction it is reduced to oxygen. For example, let's put silver nitrate into pure hydrogen peroxide, then the products of this reaction will be silver, gaseous oxygen (which immediately evaporates) and nitric acid. The compound now discussed is unstable and therefore can easily decompose. Spontaneously disproportionates to water and oxygen when mixed with dilute solutions. However, in its pure form, hydrogen peroxide is a very stable substance. If a concentrated solution of this compound acts on some hydroxides, then the reaction ends with the formation of metal peroxides, which are considered as its salts. Hydrogen peroxide is a reactive form of oxygen, and its increased production in the cell leads to oxidative stress. In a living organism, it can be obtained due to the redox reactions of certain enzymes, where it plays a protective role as a bactericidal agent. Mammals do not have the enzymes that reduce hydrogen peroxide from oxygen. However, some enzyme systems can produce superoxide, which is subsequently converted into the desired substance.
Obtaining hydrogen peroxide
In industry, hydrogen peroxide is formed in reactions involving organic substances, for example, catalytically oxidizing isopropyl alcohol. In addition to the desired peroxide, this process also produces a valuable by-product - acetone. Hydrogen peroxide is also formed during the electrolysis of sulfuric acid. In the laboratory, it is obtained by the interaction of barium oxide and sulfuric acid. The products of this reaction are barium sulfate and the desired peroxide. It is concentrated and purified by careful distillation.
Application
Textile and paper making use hydrogen peroxide as a bleach. It is also needed as rocket fuel and to drive turbopump units. Hydrogen peroxide is also necessary in analytical chemistry as a catalyst, epoxidizing and hydrogenating agent, and also as a foaming agent, which is used to produce porous materials, disinfectants and bleaching agents. This peroxide cleans wounds, bleaches hair and whitens teeth. The food industry also owes a lot to hydrogen peroxide solutions, as they disinfect the technological surfaces of equipment that are in direct contact with products, as well as packaging. This peroxide is also capable of removing stains of tetravalent manganese oxide, and this property is widely used in everyday life.
Conclusion
That's how useful hydrogen peroxide is. As you can see, it is needed not only in medicine, but also in many other industries.
