ASTM: D1126: Hardness in Water
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Official Method Name
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Standard Test Method for Hardness in Water |
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Current Revision
| 1996 |
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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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Calcium and magnesium ions in water are sequestered by the addition of disodium ethylenediamine tetraacetate. The end point of the reaction is detected by means of Chrome Black T , which has a red color in the presence of calcium and magnesium and a blue color when they are sequestered. |
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Scope and Application
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This test method covers the determination of hardness in water by titration. This test method is applicable to waters that are clear in appearance and free of chemicals that will complex calcium or magnesium. It is possible to differentiate between hardness due to calcium ions and that due to magnesium ions by this test method. |
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Applicable Concentration Range
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> 2 mg/L |
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Interferences
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The substances shown in Table 1 represent the highest concentrations that have been found not to interfere with this determination. The test method is not suitable for highly colored waters, which obscure the color change of the indicator. |
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Quality Control Requirements
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Not Included |
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Sample Handling
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Collect the sample in accordance with Practice D 1066 or Practice D 3370 as applicable. |
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Maximum Holding Time
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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