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IMPROVED METHODS OF ANALYSIS FOR CHLORATE, CHLORITE, AND HYPOCHLORITE IONS AT THE SUB-MG/L LEVEL
Citation:
Gordon, G. IMPROVED METHODS OF ANALYSIS FOR CHLORATE, CHLORITE, AND HYPOCHLORITE IONS AT THE SUB-MG/L LEVEL. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/4-85/074.
Description:
A modified iodometric method is reported to measure chlorate ion at the sub-mg/L level with high precision and accuracy. Hexane and nitrogen are used as shielding agents. Chlorate ion is reduced by iodide ion in 6M hydrochloric acid. Saturated sodium phosphate solution is used to lower the hydrogen ion and the liberated iodine is titrated with standard sodium thiosulfate. The end-point is detected using Thyodene as the indicator or by the color of iodine in the hexane layer. An analytical scheme is reported to speciate hypochlorite, chlorite, and chlorate ions in a mixture at the sub-mg/L level. Chlorate ion is determined directly by a modified iodometric method. Chlorite ion is determined directly by the modified Suzuki-Gordon method where the chlorine and hypochlorous acid are converted to hypochlorite ion. The titration end-point is determined by a potentiometric method.