This test allows a quick and easy method to determine the free/available chlorine in solution.Chlorine is often seen for use in swimming pools and water supply systems. At the right concentrations it can safely be used to prevent the growth of harmful microorganisms and remove impurities. Regular checks are required to ensure that the correct levels of chlorine are being maintained.In water chlorine occurs as either free chlorine or bound chlorine; the combination of which is total chlorine.