Hydrogen Peroxide
Overview
Hydrogen peroxide (HY-druh-jin per-OK-side) is a clear, colorless, somewhat unstable liquid with a bitter taste. When absolutely pure, the compound is quite stable. Even small amounts of impurities (such as iron or copper), however, act as catalysts that increase its tendency to decompose, sometimes violently, into water and nascent oxygen (O). To prevent decomposition, small amounts of inhibitors, such as acetanilide or sodium stannate are added to pure hydrogen peroxide and hydrogen peroxide solutions.
Key Facts
Other Names:
Hydrogen dioxide; hydroperoxide; peroxide
Formula:
H2O2
Elements:
Hydrogen; oxygen
Compound Type:
Oxide (inorganic)
State:
Liquid
Molecular Weight:
34.02 g/mol
Melting Point:
−0.43°C (−31°F)
Boiling Point:
150.2°C (302.4°F)
Solubility:
Very soluble in water; soluble in ether
Hydrogen peroxide was discovered in 1818 by French chemist Louis Jacques Thénard (1777–1857). It was first used commercially in the 1800s, primarily to bleach hats. Today, industrial processes make about 500 million kilograms (1 billion pounds) of hydrogen peroxide annually for use in a wide variety of applications ranging from whitening of teeth to propelling rockets.
How It Is Made
Hydrogen peroxide occurs in very small amounts in nature. It is formed when atmospheric oxygen reacts with water to form H2O2. Hydrogen peroxide is also present in plant and animal cells as the byproduct of metabolic reactions that occur in those cells.
The large amounts of hydrogen peroxide used in industry are prepared in a complex series of reactions that begins with any one of a family of compounds known as the alkyl anthrahydroquinones, such as ethyl anthrahydroquinone. The anthrahydroquinones are three-ring compounds that can be converted back and forth between two or more similar structures. During the conversion from one structure to another, hydrogen peroxide is produced as a byproduct. The anthraquinone is continuously regenerated during the production of hydrogen peroxide, making the process very efficient.
Other methods for the preparation of hydrogen peroxide are also available. For example, the electrolysis of sulfuric acid results in the formation of a related compound, peroxy-sulfuric acid (H2SO5), which then reacts with water to form hydrogen peroxide. A third method of preparation involves the heating of isopropyl alcohol [2-propanol; (CH3)2CHOH] at high temperature and pressure, resulting in the formation of hydrogen peroxide as one product of the reaction.
Common Uses and Potential Hazards
Most of hydrogen peroxide's applications depend on the fact that it tends to break down, releasing a single atom of nascent oxygen (O):
H2O2 → H2O + (O)
The term nascent oxygen refers to a single atom of oxygen, a structure that is chemically very active. Nascent oxygen tends to be a very strong oxidizing agent. For example, the use of hydrogen peroxide with which most people are probably familiar is as an antiseptic, a substance used to kill germs. Hydrogen peroxide achieves this result because the nascent oxygen it releases destroys bacteria, fungi, and other microorganisms that cause disease.
Interesting Facts
- Hydrogen peroxide is sold in concentrations ranging from 3 percent (for home use) to 90 percent (for industrial applications).
- Scientists have discovered hydrogen peroxide in the atmosphere of Mars.
The most important industrial application of hydrogen peroxide—its use in the pulp and paper industry—also depends on its oxidizing properties. In this case, it is used to bleach the materials of which paper is made, converting colored compounds to colorless compounds. About 55 percent of all hydrogen peroxide made in the United States is used for this purpose. Another nine percent is used in the bleaching of other materials, such as textiles, furs, feathers, and hair. Another important application of hydrogen peroxide is in water and sewage treatment plants, where its antibacterial action destroys disease-causing organisms in the water. Some additional uses of hydrogen peroxide include:
- In bakeries to condition dough and make it easier to work with;
- For cleaning metals;
- As a rocket propellant;
- In the preparation of other organic and inorganic compounds;
- As a neutralizing agent in the production of wines; and
- As a disinfectant in the treatment of seeds for agricultural purposes.
The hydrogen peroxide solutions with which people come into contact at home pose little or no health hazard because the concentration of the compound is very low, usually about3 percent. Prolonged use of hydrogen peroxide may cause burns on the skin, however, and the more concentrated solutions used in industry present more serious hazards. They can be toxic if ingested and are explosive if not stored properly.
Words to Know
A material that increases the rate of a chemical reaction without undergoing any change in its own chemical structure. A substance added to another substance to prevent or slow down an unwanted reaction. A process that includes all of the chemical reactions that occur in cells by which fats, carbohydrates, and other compounds are broken down to produce energy and the compounds needed to build new cells and tissues. A chemical reaction in which oxygen reacts with some other substance or, alternatively, in which some substances loses electrons to another substance, the oxidizing agent.For Further Information
"Hydrogen Peroxide (>60% Solution in Water)." International Labour Organization. http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc01/icsc0164.htm (accessed on October 12, 2005).
"Introduction to Hydrogen Peroxide." U.S. Peroxide. http://www.h202.com/intro/overview.html (accessed on October 12, 2005).
"A Prescription for Death?" CBSNews.com http://www.cbsnews.com/stories/2005/01/12/60II/main666489.shtml (accessed on October 12, 2005).
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