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.