What percentage of Chlorine is available at a pH level of 7.2?

The percentage of available chlorine at a pH level of 7.2 is approximately 66%. This value is significant because it reflects the balance between free available chlorine, primarily in the form of hypochlorous acid (HOCl), and combined chlorine. As the pH of water changes, the relative proportions of these different forms of chlorine also change, impacting the effectiveness of disinfection.

At a lower pH, more chlorine exists as hypochlorous acid, which is the form most effective for disinfection due to its strong oxidizing properties. At a pH around 7.2, which is close to the ideal range for optimal disinfection, 66% of the chlorine remains available and ready to effectively eliminate pathogens. As pH increases beyond this level, the effectiveness of chlorine decreases since more of it converts into hypochlorite ions (OCl-), which are less effective as a disinfectant.

Understanding the relationship between pH and chlorine availability is crucial in water treatment and sanitation practices, as it helps ensure that disinfection efforts are effective in maintaining safe water quality.