peroxide, chemical compound containing two oxygen atoms, each of which is bonded to the other and to a radical or some element other than oxygen; e.g., in hydrogen peroxide, H₂O₂, the atoms are joined together in the chainlike structure H-O-O-H. Peroxides are powerful oxidizing agents. They are unstable, releasing oxygen when heated. Peroxides may be formed directly by reaction of an element or compound with oxygen. In dry, carbon-dioxide-free air, sodium or barium metal reacts to form its peroxide. In moist air, zinc metal is oxidized and hydrogen peroxide is formed. When a metal peroxide is treated with a dilute acid, a solution of hydrogen peroxide and a metal salt is formed. Ethers can react with oxygen from the air to form peroxides. This creates a special hazard, since the peroxides are often so unstable that they decompose explosively if heated.

hydrogen peroxide, chemical compound, H₂O₂, a colorless, syrupy liquid that is a strong oxidizing agent and, in water solution, a weak acid. It is miscible with cold water and is soluble in alcohol and ether. Although pure hydrogen peroxide is fairly stable, it decomposes into water and oxygen when heated above about 80°C;; it also decomposes in the presence of numerous catalysts, e.g., most metals, acids, or oxidizable organic materials. A small amount of stabilizer, usually acetanilide, is often added to it. Hydrogen peroxide has many uses. It is available for household use as a 3% (by weight) water solution; it is used as a mild bleaching agent and medicinally as an antiseptic. The 3% solution is sometimes called ten volume strength, since one volume of it releases ten volumes of oxygen when it decomposes. Hydrogen peroxide is available for commercial use in several concentrations. Highly concentrated solutions were first used in World War II by the military, e.g., in fuels for rockets and torpedoes. It is used as a bleaching agent for textiles, e.g., wool and silk, and in paper manufacture. It is also used in chemical manufacture. Hydrogen peroxide is prepared commercially by oxidation of alkylhydroanthraquinones and by electrolysis of ammonium bisulfate. It can also be prepared by reaction of barium peroxide with sulfuric acid and is prepared (with acetone) by oxidation of isopropanol. Hydrogen peroxide was discovered (1818) by L. J. Thenard.

Any of a class of chemical compounds in which two oxygen atoms are linked by a single covalent bond. Several organic (see organic compound) and inorganic (see inorganic compound) peroxides are useful as bleaching and oxidizing agents (see oxidation-reduction), as initiators of polymerization reactions, and in the preparation of hydrogen peroxide (a mild bleach and antiseptic) and other oxygen compounds. The peroxide anion (chemical formula O₂²⁻) is present in peroxides of inorganic compounds.

Learn more about peroxide with a free trial on Britannica.com.