Fentons reagent is a solution of hydrogen peroxide (HO) and an iron catalyst (typically iron(II) sulfate, FeSO). It is used to oxidize contaminants or waste water as part of an advanced oxidation process. Fentons reagent can be used to destroy organic compounds such as trichloroethylene and tetrachloroethylene (perchloroethylene). It was developed in the 1890s by Henry John Horstman Fenton as an analytical reagent.