Hydrogen peroxide is made commercially by the cyclic reduction and oxidation of solutions containing alkyl-substituted anthraquinones. Such solutions contain not only the alkyl anthraquinone, but also certain oxidation and reduction products which do not revert to the active compounds in the plant working solution, and which thus reduce the efficiency of the plant for the production of hydrogen peroxide. Section 2 examines the chemistry involved in the hydrogen peroxide manufacturing process and degradation routes of the various active materials. The identification and quantitation of the components of the working solution is thus of considerable significance in the economic production of industrially important hydrogen peroxide.