Hydrogen peroxide (H₂O₂) is widely used as a disinfectant and as a bleach for textiles, wood pulp, and hair, just to name a few. It is also used as a substitute for chlorine in water and sewage treatment. Most common commercial forms are aqueous solutions containing about 6, 12, and 30% hydrogen peroxide and are referred to as "20-volume," "40-volume," and "100-volume" respectively, referring to the value of oxygen liberated when the solution is boiled.
Hanna Instruments offers a chemical test kit that can quickly and easily determine concentration of hydrogen peroxide in water up to 10 mg/L. The chemical test kit uses an iodometric titration method to measure hydrogen peroxide 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 hydrogen peroxide in the sample. The concentration of iodine is then calculated by titration of thiosulfate ions that reduce the iodine back to iodide ions.