Abstract: This invention relates to a biocidal composition comprising water, a source of chlorite ions, a source of chloride ions and a source of chlorate ions where the mol ratio of chlorite ions to chlorate ions is in the range from about 2:1 to about 1000:1, the mol ratio of chlorite ions to chloride ions is from about 0.1:1 to about 1000:1 and the mol ratio of chloride ions to chlorate ions is in the range from about 0.1:1 to about 1000.1; the chlorite ion source present in amounts of from about 40 grams to about 0.04 milligrams per thousand grams of water; and the composition including a pH adjusting material in an amount sufficient to adjust the pH of the mixture to above 7.0. Thus the composition avoiding the formation of significant amounts of chlorine dioxide or stabilized chloride dioxide.