Abstract: The invention relates to an enveloping membrane for discharging an enclosed agent in an aqueous medium. The aqueous solution of an oxidizing chlorine-oxygen compound is enclosed is said enveloping membrane which is insoluble in a neutral aqueous medium. In an advantageous embodiment, the enveloping membrane represents a capsule structure, particularly according to the core/shell principle. The core has a spongy, moist structure and contains the aqueous solution of an oxidizing chlorine-oxygen compound while the shell is water-insoluble and is provided with pores to discharge the chlorine-oxygen compound over an extended period of time, particularly in an aqueous medium.