EPA-NERL: 330.3: Total Residual Chlorine by Titration
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Official Method Name
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Chlorine, Total Residual (Titrimetric, Iodometric) |
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Current Revision
| Issued 1978 |
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Media
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WATER |
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Instrumentation
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Titration |
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Method Subcategory
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Inorganic |
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Method Source
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Citation
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Brief Method Summary
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Chlorine (hypochlorite ion, hypochlorous acid) and chloramines stoichiometrically liberate iodine from potassium iodide at pH 4 or less. The iodine is titrated with a standard reducing agent such as sodium thiosulfate or phenylarsine oxide using a starch indicator. The results are calculated as mg/L Cl even though the actual measurement is of total oxidizing power because chlorine is the dominant oxidizing agent present. |
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Scope and Application
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The iodometric titration method is applicable to natural and treated waters at concentrations greater than 0.1 mg/L. |
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Applicable Concentration Range
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Greater than 0.1 mg/L. |
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Interferences
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Ferric, manganic and nitrite ions interfere, the neutral titration minimizes these interferences. Acetic acid is used for the acid titration. Sulfuric acid may be used if no interferences are present. Hydrochloric acid should never be used. Turbidity and color may make the endpoint difficult to detect. Practice runs with spiked samples may be necessary. |
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Quality Control Requirements
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None. |
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Sample Handling
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None. |
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Maximum Holding Time
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Analyze Immediately. |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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None. |
