Can hypochlorous acid be made from chlorine bleach?


Hypochlorous acid can be made from chlorine bleach by dilution however there are limitations. Hypochlorous acid is almost nonexistent in a free chlorine solution with a pH above 9. Chlorine bleach has a pH above 13. By diluting chlorine bleach, the pH can be lowered however the concentration of free chlorine will also be lowered. Upon diluting chlorine bleach to pH 8.5, the percent of the free chlorine that is hypochlorous acid is less than 5%. More dilution will dilute the free available chlorine concentration to unuseful levels. Trying to lower the pH with acidifiers will not help either because chlorine bleach will react violently and the free available chlorine product will be lost as chlorine gas. Therefore, electrolysis is the only safe method for generating high concentrations of acidic-to-neutral pH free chlorine solutions that are dominated by hypochlorous acid. At pH 5, the percent of free chlorine that is hypochlorous acid is above 99%.