In water, chlorine dioxide is the active sanitizing compound. It differs from hypochlorous acid in several significant ways. Chlorine dioxide is uniformly active across a wide pH range, while the germicidal activity of hypochlorous acid varies with the pH of the solution. Hypochlorous acid becomes ineffective above pH 8.5, but chlorine dioxide retains some sanitizing power up to pH 10.0. Chlorine dioxide is a stronger oxidizer than other chlorine sanitizers and it is less likely to form chlorinated organic compounds.
Chlorine dioxide is desirable whenever the organic load of the water is high.
In addition, chlorine dioxide removes iron, manganese, odors, flavors, and colors from the water. Concentrations of chlorine dioxide can be easily measured by a test kit. Chlorine dioxide is more expensive than chlorine gas or hypochlorites. Chlorine dioxide decahydrate may be commercially prepared, but must be refrigerated because it decomposes at room temperature and can explode under certain conditions. Iodine Compounds Iodophors are a combination of iodine and a solubilizing agent that releases free iodine when diluted with water.