What happens when peroxide dissolves in water



Structural formula
General
Surname Hydrogen peroxide
other names

μ-1κO, 2κO’-hydrogen dioxide, perhydrol, hydrogen peroxide (obsolete)

Molecular formula H2O2
CAS number 7722-84-1 (aqueous solution)
Brief description colorless liquid
properties
Molar mass 34.02 g mol−1
Physical state liquid
density 1.45 g cm−3(20 ° C, pure)[1]
1.11 g cm−3 (20 ° C, 30%)[1]
Melting point −0.41 ° C (pure)[1]
−33 ° C (35%)[1]
−11 ° C (90%)[1]
boiling point 150.2 ° C (pure)[1]
108 ° C (35%)[1]
142 ° C (90%, with decomposition)[1]
Vapor pressure

1.9 hPa (20 ° C)[1]

solubility

completely miscible with water

safety instructions
MAK

0.5 ml x m−3 and 0.71 mg · m, respectively−3[1]

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions.

Hydrogen peroxide (H2O2) is a pale blue, in diluted form colorless, largely stable liquid compound made of hydrogen and oxygen. It is a little more viscous than water, a weak acid and, compared to most substances, a very strong oxidizing agent. B. copper, brass, potassium iodide reacts and thus acts as a strong bleach and disinfectant. In highly concentrated form, it can be used both as a single and as a component rocket propellant.

Physical Properties

The H2O2-Molecule is angled (dihedral angle = 111 °). Because of the strong cross-linking through hydrogen bridges, pure hydrogen peroxide is very viscous. Since highly concentrated (= almost anhydrous) H2O2 is unstable and spontaneously disintegrates with an explosion, especially when it comes into contact with metals, it is usually sold over the counter as a maximum 35% solution in water. For industrial use, however, there are also concentrations of 50% H2O2 in water.

Contact with hydrogen peroxide solution in excess of 20% can cause chemical burns. Protective gloves must therefore be worn when handling.

Manufacturing

In the past, hydrogen peroxide was mainly produced by the electrolysis of sulfuric acid. Peroxodisulfuric acid is formed, which is then hydrolyzed again to sulfuric acid and hydrogen peroxide.

Today, hydrogen peroxide is technically produced using the anthraquinone process. For this purpose, anthrahydroquinone is converted into hydrogen peroxide and anthraquinone with atmospheric oxygen under pressure. In the next step, anthraquinone can be reduced again to anthrahydroquinone with hydrogen, etc. The gross equation is:

On a laboratory scale, hydrogen peroxide is also produced when peroxides are treated with acids. A historically important reactant is barium peroxide, which reacts in a sulfuric acid solution to form hydrogen peroxide and barium sulfate.

The molar enthalpies of formation are:

  • ΔfH0gas: −136.11 kJ / mol
  • ΔfH0liq: −188 kJ / mol
  • ΔfH0Sol: −200 kJ / mol

Chemical properties

Hydrogen peroxide tends to break down into water and oxygen. An energy of 98.02 kJ / mol is released:

Disproportionation of two molecules of hydrogen peroxide to form water and oxygen.

This decomposition reaction is caused, among other things, by Mn2+- (see proof) or other heavy metal ions, I.- and OHIons catalyzed. Therefore, H2O2-Solutions in the trade with stabilizers (including phosphoric acid) added. It is a powerful oxidizer. When the oxidation state is reduced from −I to −II, the only reaction products are water and oxygen. Difficult to separate or disruptive by-products are not produced, which simplifies its use in the laboratory.

Compared to stronger oxidizing agents (e.g. potassium permanganate) it can also act as a reducing agent.

Hydrogen peroxide is a very weak acid; its inorganic salts and organic esters are the hydroperoxides and peroxides.

proof

For qualitative proof, the neutral sample solution Mn2+Ions (for example MnSO4) admitted. If gas develops, the glow chip test is used to test for oxygen. If this turns out to be positive, in that the glow chip glows, it was H2O2 present.

Evidence as chromium peroxide (CrO (O2)2)

Make of the festival rehearsal. Chromium trioxide CrO3 results with hydrogen peroxide in the strongly acidic range (pH < 0) das="" intensiv="" blau="" gefärbte="" chromperoxid,="" welches="" sich="" in="" ether="" löst.="" hierzu="" kaliumdichromat="" mit="" verd.="">2SO4 acidify and cover 1 cm high with ether (deduction!), add sample and shake. The ether phase turns bluish in color.

Detection as peroxotitanyl (IV) ion ([Ti (O2)OH+])

The detection with "titanium yellow" (not to be confused with a dye of the same name) is a very sensitive one. (Colorless) titanium (IV) ions produce the intense orange-yellow colored peroxotitanyl ion even with traces of hydrogen peroxide. Conversely, a substance can therefore also be tested for titanium (IV) with hydrogen peroxide.

Detection with potassium permanganate

To determine the concentration in aqueous solutions, e.g. B. bleach baths. The determination is carried out oximetrically with n / 10 potassium permanganate solution in sulfuric acid solution (change to a permanent pale pink color (lasting approx. 1 min) according to the following equation:

physiology

Hydrogen peroxide is very corrosive, especially in the form of steam. If you get hydrogen peroxide on the skin, you should rinse the area well with water (dilution), or at least remove it from the skin immediately. It quickly kills the skin cells, which then turn white.

In general, hydrogen peroxide has a cytotoxic effect and, due to its high toxicity, disinfects many prokaryotic microorganisms.

Hydrogen peroxide is produced in numerous biochemical processes. In the biological cycle it arises from the oxidative metabolism of sugar. The organism protects itself against its toxic effects with the help of enzymes - catalases, peroxidases - which turn it back into non-toxic O2 and H2O decompose.

After being fertilized by a sperm, the female egg briefly produces low concentrations of hydrogen peroxide in order to kill other sperm.

In addition, hydrogen peroxide is a signaling molecule for the induction of the plant's defense against pathogens (aspect of cytotoxicity).

use

Bleach

Hydrogen peroxide is a bleaching agent, so it is used in cosmetics for bleaching hair and bleaching teeth. It is often used as a peroxide bound to carbamide.

Platinum blonde, the maximum avoidance of color in hair, mankind owes to hydrogen peroxide. The extremely reactive liquid destroys the color pigments in the hair.[2]

The world's largest application can be seen in the environmentally friendly bleaching of pulp. Cellulose is obtained from wood and the lignin it contains with H2O2 bleached. The main use of cellulose is the manufacture of paper, napkins, handkerchiefs, etc.

In the trade, hydrogen peroxide is used to bleach - i.e. to lighten - wood, e.g. B. in restoration or renovation.

Hydrogen peroxide or bleaching agents containing hydrogen peroxide, such as a peroxyacetic acid-hydrogen peroxide mixture, are also used in advertising language using the made-up word Active oxygen designated.

Disinfection and sterilization

For disinfection, hydrogen peroxide is used as a three percent solution in the mouth and throat, e.g. B. in dentistry; It is also used for disinfecting contact lenses in contact lens cleaners and for disinfecting packaging materials as well as for hand disinfection. It is also used in skin creams for the face, to open pores and thus fight pimples and blemishes. It is often used for cleaning industrial wastewater and in swimming pool technology for disinfecting water.

In the food industry, 30% hydrogen peroxide is used in aseptic filling systems for the sterilization of PET bottles. Numerous foods (beverages, milk, dairy products, sauces, soups, etc.) are aseptically packaged in cartons, cups, bottles and foils to improve shelf life and product quality. The most frequently used process is based on sterilization with concentrated hydrogen peroxide (35%). The high bactericidal effect of H2O2, the environmental compatibility and the good technical feasibility are the reasons for the widespread use of this process. In operational practice, a distinction is made between spray and immersion bath processes.

Oxygen supply

Hydrogen peroxide can be used to supply oxygen in aquariums. Oxygen is generated in an oxidizer. For this purpose, hydrogen peroxide is split into water and oxygen radicals in a vessel in the aquarium with the help of a catalyst.

Use of several effects at the same time

During interior renovations, hydrogen peroxide can be used to combat mold growth. It can - as a disinfectant - kill the biologically active cells (fungicide) and destroy the spores (sporicide). As a bleach it can also Not Make removed residues of the covering - on a white, porous surface - "optically harmless". Hydrogen peroxide is preferable to alcohol or sodium hypochlorite, as these substances are by-products, such as B. can generate salts in the subsurface. Compared to hydrogen peroxide, alcohol is neither sporocidal nor bleaching.

Hydrogen peroxide is also used for bleaching and disinfecting when preparing bones. In dentistry, H2O2 Used for local disinfection of the tooth tissue and for hemostasis in smaller operations.

In agriculture, hydrogen peroxide is used to disinfect greenhouses and for oxygen enrichment in nutrient solutions from hydroponics.

biology

To determine bacterial cultures, the catalase test is carried out with a 3% hydrogen peroxide solution. Most aerobic and facultative anaerobic bacteria as well as fungi have the enzyme catalase, which is capable of producing H.2O2 to split.

Hydrogen peroxide can be used in forensics to detect blood. Louis Jacques Thenard discovered in 1818 that the peroxidase in hemoglobin decomposes hydrogen peroxide. Christian Friedrich Schönbein developed a test for blood from this in 1863. Today, however, the more sensitive Kastle-Meyer test is used to detect blood.

Hydrogen peroxide is used experimentally in biology to induce programmed cell death in isolated eukaryotic cells.

Caustic

In microelectronics, a mixture of sulfuric acid and hydrogen peroxide - called "piranha" - is used to clean the surface of wafers and to create a thin, 3–4 nm thick, hydrophilic oxide layer on the wafers. Nowadays the name "SPM" (Sulfuric Peroxide Mixture) is more common. The main application is the removal of photoresist.

In the manufacture of printed circuit boards (circuit boards), copper chloride etching baths are used to remove the copper:

.
Elemental copper reacts with copper (II) chloride to form copper (I) chloride. This is a comproportioning.

To regenerate the copper chloride etching baths, hydrogen peroxide is used together with hydrochloric acid:

.
The copper (II) chloride is regenerated by reacting the copper (I) chloride with hydrogen peroxide and hydrochloric acid. The copper atom is oxidized in the process.

The addition of hydrogen peroxide and hydrochloric acid is controlled via the redox potential.

Rocket / torpedo engines

It was used in concentrated form as a source of energy or oxygen (decomposition via manganese dioxide) in rocket propulsion systems (such as: Max Valier, Messerschmitt Me 163) and submarine propulsion systems (Walter submarine). Hydrogen peroxide, which was decomposed with the help of potassium permanganate, was also used as a propellant for the fuel pumps (500 hp) of the A4. Undecomposed hydrogen peroxide was used as a liquid oxygen carrier at normal temperature in British rockets (e.g. Black Arrow) and burned there with kerosene.

Hydrogen peroxide tends to decompose in an uncontrolled manner. On July 16, 1934, Dr. Kurt Wahmke and two technicians in Kummersdorf during the explosion of an engine powered by hydrogen peroxide. Due to the dangerousness in use and handling (corrosive effects, uncontrolled decomposition, explosion in the case of contamination in the tank and pipe system), use today is limited to small rocket engines (record attempts, control engines).

The sinking of the Russian nuclear submarine Kursk in 2000 it was rumored to have been caused by a leak of hydrogen peroxide from a tank in a torpedo and subsequent reaction with copper parts that caused the torpedo to burst.

Explosives manufacture

In the presence of a suitable catalyst, hydrogen peroxide reacts with acetone to form acetone peroxide. Acetone peroxide is an explosive, but it is not used commercially because of its unsafe handling. More precisely, acetone peroxide is also known as triacetone triperoxide, or TATP for short. Other explosives made with hydrogen peroxide include hexamethylene triperoxide diamine (HMTD).

According to experts at the Fraunhofer Institute for Chemical Technology, TATP is used in most suicide bombings in Israel.[3] The attacks of July 7, 2005 on the London Underground (55 dead) are also said to have been carried out with TATP. Finally, on September 4, 2007, three Islamists trained in Pakistan were arrested in Oberschledorn in the Sauerland region who wanted to produce TATP from 730 kilograms of a 35% hydrogen peroxide solution in order to attack US facilities and restaurants in Germany that were frequented by US citizens.[4][5][6]

On the other hand, experts do not know in detail how terrorists could detonate TATP produced with hydrogen peroxide in a controlled manner. Above all, after a failed attempt to smuggle liquid explosives into an airplane in London in 2007, it was doubted that suitable acetone peroxide could be produced on board using smuggled vials of hydrogen peroxide and acetone.[7]

literature

  • Werner R. Thiel: New ways to hydrogen peroxide: alternatives to established processes? Angewandte Chemie 111 (21), pp. 3349-3351 (1999)
  • Heribert Offermanns, Gunther Dittrich, Norbert Steiner: Hydrogen peroxide in environmental protection and synthesis. Chemistry in our time 34 (3), pp. 150-159 (2000), ISSN 0009-2851

References

  1. abcdefGHij Entry to Hydrogen peroxide in the GESTIS substance database of the BGIA, accessed on November 16, 2007 (JavaScript required)
  2. Süddeutsche Zeitung of September 6, 2007, p. 2: "Current lexicon: Hydrogen peroxide". Drawn: mkf
  3. The information in this paragraph is based on that of mkf signed article "Current Lexicon: Hydrogen peroxide“On p. 2 of the Süddeutsche Zeitung from 9/6/2007.
  4. Süddeutsche Zeitung of September 6, 2007, p. 1f.
  5. netzeitung.de
  6. rundschau-online.de
  7. This paragraph refers to oraclesyndicate - Karl Weiss and the Wikipedia article acetone peroxide.

Categories: Oxidising substances | Corrosive substance | Hydrogen compound | Oxygen compound | Drug