Encyclopedia > Hydrogen peroxide

  Article Content

Hydrogen peroxide

Properties
General
Name Hydrogen peroxide
Chemical formula H2O2
Appearance Colourless liquid
Physical
Formula weight 34.0 amu
Melting point 272.6 K (-0.4 °C)
Boiling point 423 K (150 °C)
Density 1.4 ×103 kg/m3
Solubility miscible
Thermochemistry
ΔfH0gas -136.11 kJ/mol
ΔfH0liquid -188 kJ/mol
ΔfH0solid -200 kJ/mol
S0gas, 1 bar 232.95 J/mol·K
S0liquid, 1 bar 110 J/mol·K
S0solid ? J/mol·K
Safety
Ingestion Serious injury, death possible.
Inhalation Severe irritation, death possible.
Skin Causes bleaching—flush immediately.
Eyes Dangerous.
More info Hazardous Chemical Database (http://ull.chemistry.uakron.edu/erd/chemicals/7/6584)
SI units were used where possible. Unless otherwise stated, standard conditions were used.

Disclaimer and references

The chemical compound hydrogen peroxide (H2O2) is a viscous liquid that has strong oxidizing properties and is therefore a powerful bleaching agent[?] that has found use as a disinfectant[?] and (in strong concentrations) as an oxidizer[?] or monopropellant in rockets.

It is commonly used (in very low concentrations, such as 5%) to bleach human hair, hence the phrases "peroxide blonde" and "bottle blonde". It burns the skin if it comes into contact in sufficient concentration. In lower concentrations, it is used medically for cleaning wounds and removing dead tissue.

Hydrogen peroxide tends to decompose exothermically into water and oxygen gas. The rate of decomposition is dependent on the temperature and concentration of the peroxide, as well as the presence of impurities and stabilizers. The ability of peroxide to coexist with a substance is called compatibility. Peroxide is incompatible with many substances, including most of the transition metals (i.e. iron, copper, silver, cobalt, etc.) and their compounds, many organic compounds, dirt, human beings, etc. Spilling high concentration peroxide on an flammable substance can cause an immediate fire.

The use of a catalyst (such as manganese dioxide, silver, or the enzyme catalase) vastly increases the rate of decomposition of hydrogen peroxide. High strength peroxide (also called high-test peroxide, or HTP) must be stored in a vented container to prevent the buildup of pressure leading to the eventual rupture of the container. Any container must be made of a compatible material such as polyethylene or aluminum (not stainless steel) and be cleaned of all impurities (a process sometimes referred to as passivation) prior to the introduction of peroxide.

Hydrogen peroxide has also been used as a propellant[?]. Its use in torpedoes has been discontinued by most navies due to safety considerations. A hydrogen peroxide leak was blamed for the sinkings of HMS Sidon and the Russian submarine Kursk.

Hydrogen peroxide works best as a propellant in extremely high concentrations. However, there are very few suppliers of high purity hydrogen peroxide, and they are averse to selling to any but the largest institutions. As a result, amateurs wishing to use this for rocket fuel usually have to purchase 70% or lower purity (most of the remaining 30% is water, and sometimes there are traces of stabilizing materials, such as tin, to reduce the decomposition rate), and increase its concentration themselves, since 70% makes for extremely poor propellant compared to 90% or better. Many try distillation, but this is extremely dangerous with hydrogen peroxide.

A safer approach is sparging, possibly followed by fractional freezing[?]. Sparging takes advantage of the fact that warm (not hot) air will preferentially evaporate water.

In high concentrations (above 62%), hydrogen peroxide in solution with water will freeze before the water. Below 62%, the water will freeze first, until the liquid solution reaches 62%. Hydrogen peroxide tends to supercool[?], or cool below its freezing point without freezing. One way to avoid this is to drop a seed crystal of already-frozen peroxide into the supercooled solution to cause it to freeze.

Exact data on the purification of hydrogen peroxide is hard to come by, since most people with experience with this chemical know how hazardous it can be. They prefer that these amateurs calculate the numbers themselves from the basic properties, such as the freezing point of peroxide and the freezing point of water. Similar circumstances often require those who would try these experiments to lie about their intentions to the 70% hydrogen peroxide suppliers, since these companies do not wish to be seen as officially supporting hydrogen peroxide rocketry experiments.

"35 percent Food Grade Hydrogen Peroxide", which is 35% pure hydrogen peroxide, has been marketed under names such as "Oxywater" or "H2O2", with claims of medicinal or theraputic value. According to peddlers of the product, it can be diluted and used for "hyper-oxygenation therapy" to cure AIDS, cancer, and many other conditions. Some have claimed that information about these "beneficial" uses of peroxide have been suppressed by the scientific community. The US Food and Drug administration has published a warning (http://www.fda.gov/bbs/topics/NEWS/NEW00122) against the use of 35% peroxide in the home for any purpose. At least one death, and several serious injuries, have occurred as a result of ingesting this treatment.

Accidental consumption of 35% H2O2 will cause death. However 0.5% is considered safe. Many homemade "cures" are usually with the addition of colloidal silver and colloidal copper (usually at 5 parts per million. Consumption of colloidal silver can cause permanent greying of the skin (argyria). Again it must be warned that accidental consumption of peroxide at the full 35% concentration being marketed has caused deaths and serious injuries, usually to children. "This concentration is not approved by FDA for any therapeutic purpose," US FDA Commissioner Frank E. Young, M.D., Ph.D., said. "Indeed, no one has come forward with any evidence this substance taken internally has any medical value. Buyers are being cheated and subjected to significant risks and family members are being injured."

External links



All Wikipedia text is available under the terms of the GNU Free Documentation License

 
  Search Encyclopedia

Search over one million articles, find something about almost anything!
 
 
  
  Featured Article
1569

... forces under Gabriel de Montgomery[?] defeat Royalist forces under General Terride in French Navarre September - A Royalist army under the Duc d'Anjou and Marshal ...