Standard Methods: 2310 B: Acidity by Titration
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Official Method Name
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2310 B. Titration Method |
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Current Revision
| Standard Methods Online |
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Media
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WATER |
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Instrumentation
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pH Meter |
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Method Subcategory
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Physical |
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Method Source
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Citation
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Brief Method Summary
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Hydrogen ions present in a sample as a result of dissociation or hydrolysis of solutes react with additions of standard alkali. Acidity thus depends on the end-point pH or indicator used. The construction of a titration curve by recording sample pH after successive small measured additions of titrant permits identification of inflection points and buffering capacity, if any, and allows the acidity to be determined with respect to any pH of interest. |
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Scope and Application
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Applicable to wastewater, surface water, and drinking water. |
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Applicable Concentration Range
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Interferences
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Dissolved gases contributing to acidity or alkalinity, such as CO2, hydrogen sulfide, or ammonia, may be lost or gained during sampling, storage, or titration. Minimize such effects by titrating to the end point promptly after opening sample container, avoiding vigorous shaking or mixing, protecting sample from the atmosphere during titration, and letting sample become no warmer than it was at collection. In the potentiometric titration, oily matter, suspended solids, precipitates, or other waste matter may coat the glass electrode and cause a sluggish response. Do not remove interferences from sample because they may contribute to its acidity. In samples containing oxidizable or hydrolyzable ions such as ferrous or ferric iron, aluminum, and manganese, the reaction rates at room temperature may be slow enough to cause drifting end points. Do not use indicator titrations with colored or turbid samples that may obscure the color change at the end point. Residual free available chlorine in the sample may bleach the indicator. Eliminate this source of interference by adding 1 drop of 0.1M sodium thiosulfate. |
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Quality Control Requirements
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See Section 2020 Quality Assurance/Quality Control. |
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Sample Handling
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Collect samples in polyethylene or borosilicate glass bottles and store at a low temperature. Fill bottles completely and cap tightly. Because waste samples may be subject to microbial action and to loss or gain of CO2 or other gases when exposed to air, analyze samples without delay, preferably within 1 d. If biological activity is suspected analyze within 6 h. Avoid sample agitation and prolonged exposure to air. |
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Maximum Holding Time
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14 days (regulatory) |
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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