Abstract: A method of manufacturing and an apparatus for making an aqueous chlorine solution having a pH between 3.0 and 6.5 and a stability such that after 6 weeks storage at 20 degrees Celsius the pH remains in the range 3.0 to 6.5 and the amount of chlorine lost from the solution is less than 10%, such that the method includes: (a) Providing a source of water having an electrical conductivity at 20 degrees Celsius of no more than 50 (and preferably no more than 4.3) ?Scm-1 (b) Reacting the water with solid calcium hypochlorite having a purity of at least 60%; and (c) Adjusting the pH to between 3.0 and 6.5.