Abstract: A method for measuring the free chlorine content in a solution consists, in first portions of the solution, in successively adding a chemical compound (e.g. a nitrite), which selectively transforms the free chlorine into chloride, then an iodide, in introducing the said first portions in an amperometric cell for measuring the combined chlorine content and, in second portions of the solution, in adding only the iodide and subsequently introducing the second portions into an amperometric cell for measuring the total chlorine content and finally in calculating the difference between the total chlorine and the combined chlorine contents.

Abstract: For water disinfection or sterilization, for instance of drinking, municipal waste, industrial or swimming-pool waters, there is introduced in a reactor a mixture of chlorine and of a salt of another halogen (bromine and/or iodine) in such conditions that mainly free halogen and hypohalogenous acid of said other halogen are produced; the mixture is supplied to the water, in such amounts that, an halogenated residual capable of destroying microbial contamination in the system, is maintained.