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

CATALYST

A material that increases the rate of a chemical reaction without undergoing any change in its own chemical structure.

INHIBITOR

A substance added to another substance to prevent or slow down an unwanted reaction.

METABOLISM

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.

OXIDATION

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).

Hydrogen peroxide

Hydrogen peroxide is a chemical compound of hydrogen and oxygen. (It can be thought of as water with an extra oxygen atom.) Pure anhydrous hydrogen peroxide is a colorless, syrupy liquid that it rapidly decomposes into oxygen and water. Hydrogen peroxide is also a strong disinfectant cleanser and bleach. In nature, hydrogen peroxide is created in the atmosphere when ultraviolet rays strike oxygen in the presence of moisture. Ozone is free oxygen with an extra atom of oxygen. When ozone comes into contact with water, this extra atom of oxygen splits off easily. Water combines with the extra oxygen atom to become hydrogen peroxide.

Thenard's Studies

Louis Jacques Thenard (1777-1857), a French chemist, is credited with discovering hydrogen peroxide. One of the first things he found out about hydrogen peroxide is that it attacks the skin, producing painful blotches (fortunately, this effect wears off completely within a few hours). Thenard had tried for many months to formulate the chemical. At the time, however, scientists did not know how much oxygen could be combined with water. In 1818 Thenard finally succeeded in preparing pure hydrogen peroxide, which he called "oxygenated water," and determined its density.

In addition to attacking the skin, the chemical also reacts explosively with metal oxides, as Thenard soon discovered. For several years afterward, he continued to study the compound, defining its properties and using it to prepare new peroxides (other compounds containing extra oxygen).

Multiple Uses

One of the first uses of hydrogen peroxide was to restore old paintings by removing sulfur compounds from their surface. Today hydrogen peroxide has found many more valuable applications, mainly in industry but also for medical purposes. Because the chemical is a strong oxidant (it combines with other compounds to produce oxides and water), it is widely used as a commercial bleaching agent in the production of cotton, wool, and delicate fabrics that would be destroyed by other agents. Even though it costs more than chlorine bleach, hydrogen peroxide is preferred in these applications because its action on fibers is milder and it leaves no undesirable residues.

The chemical is also used cosmetically in hair bleach. In concentrated forms, hydrogen peroxide has found high-technology applications as a fuel additive for rockets, sumarines, and jet planes. In the computer industry, hydrogen peroxide has found widespread for washing transistors and integrated chip parts before assembly.

Dental and Medical Applications

Hydogen peroxide has numerous medical applications. It has long been used as an antiseptic to prevent infection and to cleanse and treat mouth sores. Today it is also used as a mouth wash and as a teeth whitener. The demand for whiter, brighter teeth became a booming business in the mid-1990s. More than a dozen products were introduced, all promising to fix yellow, stained teeth. Most of these whiteners rely on chemicals known as "oxygenating agents" to bleach teeth. The most common ingredient is a ten percent concentration of carbamide peroxide, which in contact with mouth fluids breaks down into hydrogen peroxide. This process also releases a highly reactive form of oxygen. Scientific studies have suggested that in some circumstances oxygenating agents can damage tissues and harm the pulp or interior of the teeth and even cause genetic mutations.

For years hospitals have used high-pressure steam sterilizers. These machines require temperatures too hot for many sensitive insruments. In the 1950s, hospitals began using low-temperature sterilizers, but the process was time-consuming and relied on ethylene oxide, a carcinogenic (cancer-causing) gas. In 1996 a California company, Advanced Sterilization, introduced a new instrument sterilizer for hospitals. The device is a low-temperature sterilizer fueled by a simple household chemical long used to fight infection: hydrogen peroxide.

[See also Gene ]

Hydrogen Peroxide

Hydrogen peroxide, H₂O₂, is a colorless liquid that mixes with water and is widely used as a disinfectant and a bleaching agent. It is unstable and decomposes (breaks down) slowly to form water and oxygen gas. Highly concentrated solutions of hydrogen peroxide are powerful oxidizing agents and can be used as rocket fuel.

Hydrogen peroxide is most widely found in homes in brown bottles containing 3% solutions (3% hydrogen peroxide and 97% water). The decomposition of hydrogen peroxide happens much faster in the presence of light so that an opaque bottle helps slow this process down. The decomposition of hydrogen peroxide can be summarized by the chemical equation:

2H₂O₂ → 2H₂O + O₂ + heat

which states that two molecules of hydrogen peroxide break down to form two molecules of water and one molecule of oxygen gas, along with heat energy. This process happens slowly in most cases, but once opened a bottle of hydrogen peroxide will decompose more rapidly because the built-up oxygen gas is released. A totally decomposed bottle of hydrogen peroxide consists of nothing but water. Old unopened bottles of hydrogen peroxide often bulged out from the pressure of the oxygen gas that has built up over time. Some bottles have been known to “pop” from that pressure of the oxygen gas.

The most common uses of hydrogen peroxide are as a bleaching agent for hair and in the bleaching of pulp for paper manufacturing, and as a household disinfectant. As a bleach, hydrogen peroxide is an oxidizing agent (a substance that accepts electrons from other molecules). It is becoming more widely used than chlorine bleaches in industries because the products of its decomposition are water and oxygen while the decomposition of chlorine bleaches produces poisonous chlorine gas.

As a disinfectant, hydrogen peroxide is widely used on cuts and scrapes, and produces bubbling (caused by the formation of oxygen gasmolecules). The bubbling is quite rapid on cuts because of the presence of an enzyme (a protein catalyst—or molecule that speeds up a reaction) in blood, known as catalase. A similar bubbling can be observed if a small amount of hydrogen peroxide is put on a raw sliced potato, as the enzyme catalase is also found in potatoes.

Hydrogen peroxide

Hydrogen peroxide, H2O2, is a colorless liquid that mixes with water and is widely used as a disinfectant and a bleaching agent. It is unstable and decomposes (breaks down) slowly to form water and oxygen gas. Highly concentrated solutions of hydrogen peroxide are powerful oxidizing agents and can be used as rocket fuel.

Hydrogen peroxide is most widely found in homes in brown bottles containing 3% solutions (3% hydrogen peroxide and 97% water). The decomposition of hydrogen peroxide happens much faster in the presence of light so that an opaque bottle helps slow this process down. The decomposition of hydrogen peroxide can be summarized by the chemical equation:

which states that two molecules of hydrogen peroxide break down to form two molecules of water and one molecule of oxygen gas, along with heat energy . This process happens slowly in most cases, but once opened a bottle of hydrogen peroxide will decompose more rapidly because the built-up oxygen gas is released. A totally decomposed bottle of hydrogen peroxide consists of nothing but water. Old unopened bottles of hydrogen peroxide often bulged out from the pressure of the oxygen gas that has built up over time. Some bottles have been known to "pop" from that pressure of the oxygen gas.

The most common uses of hydrogen peroxide are as a bleaching agent for hair and in the bleaching of pulp for paper manufacturing, and as a household disinfectant. As a bleach , hydrogen peroxide is an oxidizing agent (a substance that accepts electrons from other molecules). It is becoming more widely used than chlorine bleaches in industries because the products of its decomposition are water and oxygen while the decomposition of chlorine bleaches produces poisonous chlorine gas.

As a disinfectant, hydrogen peroxide is widely used on cuts and scrapes, and produces bubbling (caused by the formation of oxygen gasmolecules). The bubbling is quite rapid on cuts because of the presence of an enzyme (a protein catalyst—or molecule that speeds up a reaction) in blood , known as catalase. A similar bubbling can be observed if a small amount of hydrogen peroxide is put on a raw sliced potato , as the enzyme catalase is also found in potatoes.

hydrogen peroxide Liquid compound of hydrogen and oxygen (H₂O₂). It is prepared by electrolytic oxidation of sulphuric acid, and by methods involving reduction of oxygen. Hydrogen peroxide is used as a bleach, a disinfectant, and an oxidizer for rocket fuel and submarine propellant. Properties: r.d. 1.44; m.p. −0.9°C (30.4°F); b.p. 150°C (302°F).