Hach Co.: 8201: Acidity of Water
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Official Method Name
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Methyl Orange Acidity |
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Current Revision
| 2003 |
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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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Bromophenol blue indicator is used to titrate the sample with sodium hydroxide to a colorimetric end point. Bromophenol blue gives a better end point than methyl orange indicator. Titration to pH 3.7 determines strong mineral acidity (also referred to a methyl orange acidity. The results are expressed in mg/L as calcium carbonate (CaCO3) at a specified pH. |
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Scope and Application
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For water, wastewater, and seawater |
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Applicable Concentration Range
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10-4000 mg/L as CaCO3 |
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Interferences
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Highly colored or turbid samples may mask the color change at the end point. Use a pH meter for these samples, titrating to pH 3.7 for methyl orange acidity. Chlorine may interfere with the indicators. Add one drop of 0.1N Sodium Thiosulfate to eliminate this effect. Hydrolzable metals,such as iron, manganese or aluminium. |
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Quality Control Requirements
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Sample Handling
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Collect samples in clean plastic or glass bottles. Fill completely and cap tightly. Minimize agitation or prolonged exposure to air. Samples may be stored at least 24 hours by cooling to 4deg C. or below if they cannot be analyzed immediately. Warm to room temperature before analyzing. |
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Maximum Holding Time
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24 hours @ 4deg. C. |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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