Hypochlorites are common bleaching agents used to whiten textiles and paper and to also disinfect solutions. Sodium hypochlorite solution is used for the treatment of pool water since it is an inexpensive and readily available form of chlorine. The solution usually contains 10 to 15% available chlorine (equivalent to 100 to 150 g/L), but it rapidly loses its strength during storage. In addition, since hypochlorite is greatly affected by heat, light, pH, and heavy metals, it needs to be monitored regularly.
Hanna Instruments offers a chemical test kit that can quickly and easily determine concentration of hypochlorite in water up to 150 g/L (ppt). The chemical test kit uses an iodometric titration method to measure hypochlorite concentration in water. The sample is first treated with potassium iodide and strongly acidified with acid. The amount of iodine generated is equivalent to the chlorine in the sample. The concentration of iodine is then calculated by titration of thiosulfate ions that reduce the iodine back to iodide ions.