ASTM: D516: Sulfate in Water by Turbidimitry
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Official Method Name
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Standard Test Method for Sulfate Ion in Water |
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Current Revision
| 1990/95 |
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Media
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WATER |
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Instrumentation
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Turbidity |
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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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Sulfate ion is converted to a barium sulfate suspension under controlled conditions. A solution containing glycerin and sodium chloride is added to stabilize the suspension and minimize interferences. The resulting turbidity is determined by a nephelometer, spectrophotometer, or photoelectric colorimeter and compared to a curve prepared from standard sulfate solutions. . |
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Scope and Application
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This turbidimetric test method covers the determination of sulfate in water in the range from 1 to 40 mg/L of sulfate ion (SO42-). This test method was used successfully with drinking, ground, and surface waters. |
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Applicable Concentration Range
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1 - 40 mg/L |
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Interferences
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Insoluble suspended matter in the sample must be removed. Dark colors that can not be compensated for in the procedure interfere with the measurement of suspended barium sulfate (BaSO4). Polyphosphates as low as 1 mg/L will inhibit barium sulfate precipitation causing a negative interference. Phosphonates present in low concentrations, depending on the type of phosphonate, will also cause a negative interference. Silica in excess of 500 mg/L may precipitate along with the barium sulfate causing a positive interference. Chloride in excess of 5000 mg/L will cause a negative interference. Aluminum, polymers, and large quantities of organic material present in the test sample may cause the barium sulfate to precipitate nonuniformly. In the presence of organic matter certain bacteria may reduce sulfate to sulfide. To minimize the action of sulfate reducing bacteria, samples should be refrigerated at 4oC when the presence of such bacteria is suspected. |
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Quality Control Requirements
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Sample Handling
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Collect the sample in accordance with Practice D 1066, Specification D 1192, and Practices 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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