Spectroscopic Characterization and the pH Dependence of Bactericidal Activity of the Aqueous Chlorine Solution.

Raman spectroscopic analysis has been used to identify the chemical species that exist in aqueous chlorine solution. The pH dependence of the Raman spectra obtained indicates that there is an equilibrium among hypochlorite ion, hypochlorous acid and chlorine. Bactericidal activities of the acidic electrolyzed water, which is generated by electrolysis of an aqueous NaCl solution, were evaluated in the pH range 2 - 9 against Escherichia coli K12 and Bacillus subtilis PCI219 by a semi-quantitative bioassay. The maximum activity was observed between pH 4 and 5 in both bacteria. The Raman and the ultraviolet spectroscopic data, along with chemical analysis data, were used to conclude that the bactericidal activity is quantitatively correlated to the concentration of hypochlorous acid in solution.