Hydrogen peroxide is a chemical compound with the formula H 2 O 2 . In its pure form, it is a very pale blue,  clear liquid , slightly more viscous than water . Hydrogen peroxide is the simplest peroxide (a compound with an oxygen–oxygen single bond ). It is used as an oxidizer , bleaching agent, and antiseptic . Concentrated hydrogen peroxide, or " high-test peroxide ", is a reactive oxygen species and has been used as a propellant in rocketry .  Its chemistry is dominated by the nature of its unstable peroxide bond.