Free Available Chlorine refers to the hypochlorous acid (HOCl) form of chlorine only. It is the free, uncombined form of chlorine that is effective for disinfection. View Free Available Chlorine Analyzer – Model 875-25
Total Free Chlorine refers to the sum of hypochlorous acid (HOCl) and hypochlorite ion OCl-). The hypochlorite ion is not effective for disinfection, but it is in a free form. All of the total free chlorine would be in the form of hypochlorous acid if the pH was low enough. View Total Free Chlorine Analyzer – Model 876-25
Combined Chlorine refers to chlorine which is not readily available. For example, chlorine combined as chloramines or organic nitrogen is not an effective disinfectant and will not readily convert to hypochlorous acid or hypochlorite ion.
Total Residual Chlorine refers to the sum of total free chlorine and combined chlorine. Low total residual chlorine is of particular interest to ensure there are no downstream consequences for aquatic life. View Total Residual Oxidant Analyzer – Model 7070iX
