Hach Co.: 8219: Acidity, Methyl Orange, of Water by Buret Titration
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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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Methyl orange indicator undergoes a color change from red to orange at pH3.7 and results are commonly referred to as the methyl orange acidity. Because the methyl orange end point is difficult to see, Bromphenol Blue Solution is recommended as a replacement. Bromophenol Blue Solution gives a sharp yellow to pure green end point. Acidity also can be determined by using a pH meter to follow the solution pH to the correct end-point value as the standard base is added. |
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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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0-5000 mg/L as CaCO3 |
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Interferences
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Residual chlorine interference with the indicator may be removed by adding a drop of 0.1 N sodium thiosulfate standard solution. 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. |
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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. Avoid agitation and prolonged exposure to air. Samples should be analyzed as soon as possible after collection but can be stored at least 24 hours by cooling to 4 deg. C or below. 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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