Standard Methods: 4500-CN-D: Cyanide by Titration
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Official Method Name
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4500-CN- D. Titrimetric Method |
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Current Revision
| 1999 |
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Media
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WATER |
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Instrumentation
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Titration with Color Indicator |
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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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Cyanide in the alkaline distillate from the preliminary treatment procedure (4500-CN- B) is titrated with standard silver nitrate (AgNO3) to form the soluble cyanide complex, Ag(CN)2-. As soon as all CN- has been complexed and a small excess of Ag+ has been added, the excess Ag+ is detected by the silver-sensitive indicator, p-dimethylaminobenzalrhodanine, which immediately turns from a yellow to a salmon color. The distillation has provided a 2:1 concentration. The indicator is sensitive to about 0.1 mg Ag/L. |
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Scope and Application
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This method is suitable for various waters with cyanide concentrations above 1 mg/L. |
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Applicable Concentration Range
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Use for concentrations above 1 mg-CN-/L |
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Interferences
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Common interferences are eliminated by preliminary distillation. |
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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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Plastic or glass containers. Add NaOH to pH >12, refrigerate in the dark. |
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Maximum Holding Time
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14 days; 24 hours if sulfide is present (See Section 1060) |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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4500-CN- B |
