Hydrogen peroxide is a mild antiseptic used on the skin to prevent infection of minor cuts, scrapes, and burns.

H2O2 is the chemical formula for hydrogen peroxide. It is a very pale blue liquid that is somewhat more viscous than water in its pure state. It is used as an oxidant, bleaching agent, and antiseptic, often in a weak solution (3–6% by weight) in water for consumer use and in higher concentrations for industrial usage. Concentrated hydrogen peroxide, sometimes known as "high-test peroxide," decomposes explosively when heated and has been employed as a rocket propellant.

Hydrogen peroxide is a reactive oxygen species and the most basic peroxide, a molecule with a single oxygen–oxygen link. When exposed to light, it decomposes slowly, but quickly in the presence of organic or reactive substances. It is normally stored in a dark bottle with a stabiliser in a mildly acidic solution to inhibit light. Hydrogen peroxide can be present in biological systems such as the human body. Peroxidases are enzymes that consume or breakdown hydrogen peroxide.

Hydrogen peroxide differs from the pure material in aqueous solutions due to the effects of hydrogen bonding between water and hydrogen peroxide molecules. Hydrogen peroxide and water produce a eutectic combination with freezing points as low as –56 °C; pure water has a freezing point of 0 °C and pure hydrogen peroxide has a freezing point of 0.43 °C. The boiling point of the identical mixes is likewise lower when compared to the mean of both boiling points (125.1 °C). It happens at 114 °C. This boiling point is 14 degrees Celsius higher than pure water and 36.2 degrees Celsius lower than pure hydrogen peroxide.

Other sources

Small, but detectable, amounts of hydrogen peroxide can be formed by several methods. Small amounts are formed by electrolysis of dilute acid around the cathode where hydrogen evolves if oxygen is bubbled around it. It is also produced by exposing water to ultraviolet rays from a mercury lamp, or an electric arc while confining it in a UV transparent vessel (e.g. quartz). It is detectable in ice water after burning a hydrogen gas stream aimed towards it and is also detectable on floating ice. Rapidly cooling humid air blown through an approximately 2,000 °C spark gap results in detectable amounts.