Previous studies have suggested the possible existence of alkali cation-hypochlorite ion pairs during disinfection, paticularly at high pH. In this paper, we report quantitative measurements for the dissociation constants of the LiOCl, NaOCl, and KOCl ion pairs obtained from titration. Furthermore, we report the effect of the Li+, Na+, and K+ cations on inactivation of Escherichia coli by free chlorine. The microbiological effects are consistent, and the bactericidal efficiency of the ion pairs is estimated as intermediate between hypochlorite and hypochlorous acid. Some of the materials tested are used in conservation.