Abstract: A process to purify waste waters using chemical oxidation and Fenton's reagent by the action in the acid range of hydrogen peroxide and iron(II) compounds and subsequent precipitation in the weakly acid to alkaline range of the iron(III) compounds, said process being characterized in that the sludge containing iron(III) accumulating in addition to the purified waste water is reduced electrolytically back into iron(II) compounds and in that the sludge so reduced is fed back into the process. The process of the invention allows extensive purification of highly concentrated waste waters and furthermore problems arising with the treatment and elimination of the Fenton sludge can be circumvented.

Abstract: Stable, solid acetyl peroxyborate compounds which are active oxygen-containing compounds derived from acetic acid and boron-oxygen compounds. The compounds of the invention have a peracetic acid content which can be liberated instantly and directly in water with only minor formation of hydrogen peroxide The acetyl peroxyborates of the invention are useful in washing, bleaching and cleaning agent and disinfectant applications and as oxidizing agents in organic synthesis.

Abstract: The present invention provides a process for the production of the triple salt 2KHSO.sub.5.KHSO.sub.4.K.sub.2 SO.sub.4 from sulphuric acid, hydrogen peroxide and potassium hydroxide, wherein, for continuous production, an aqueous working solution which contains KHSO.sub.5, sulphuric acid and potassium sulphate in a molar ratio of 1.3 to 2.5/1.2 to 2.0/1, is concentrated in an evaporation plant under reduced pressure and at a temperature of maximum 40.degree. C. to a concentration which corresponds to a content of 20 to 30% by weight of KHSO.sub.5, a partial stream is removed from the concentrated solution and from this, by cooling to a temperature below 15.degree. C., the triple salt is precipitated and separated, the mother liquor obtained is combined with the remaining solution, the solution is reconstituted by the addition of 90 to 100% sulphuric acid, 30 to 90% hydrogen peroxide and concentrated aqueous potassium hydroxide solution and recycled to the evaporation plant.