Standard Methods: 4500-Cl I: Chlorine by Iodometric Electrode
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Official Method Name
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4500-Cl I. Iodometric Electrode Technique |
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Current Revision
| Standard Methods 21st Edition (2005); Standard Methods Online |
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Media
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WATER |
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Instrumentation
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Not Applicable |
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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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This method involves the direct potentiometric measurement of iodine released on the addition of potassium iodide to an acidified sample. A platinum-iodide electrode pair is used in combination with an expanded-scale pH meter. |
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Scope and Application
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This method is suitable for analysis of chlorine residuals in natural and treated waters and wastewater effluents. No differentiation of free and combined chlorine is possible. This procedure is an adaptation of other iodometric techniques and is subject to the same inferences. |
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Applicable Concentration Range
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Interferences
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All oxidizing agents that interfere with other iodometric procedures interfere. These include oxidized manganese and iodate, bromine, and cupric ions. Silver and mercuric ions above 10 and 20 mg/L interfere. |
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Quality Control Requirements
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See Section 4020 Quality Assurance/Quality Control. |
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Sample Handling
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Chlorine in aqueous solution is not stable, and the chlorine content of samples or solutions, particularly weak solutions, will decrease rapidly. Exposure to sunlight or other strong light or agitation will accelerate the reduction of chlorine. Therefore, start chlorine determinations immediately after sampling, avoiding excessive light and agitation. Do not store samples to be analyzed for chlorine. |
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Maximum Holding Time
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0.25 hour |
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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