Hach Co.: 8226: Total Hardness in Water
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Official Method Name
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Total Hardness in Water by ManVer 2 Buret Titration Using 0.020 N Titrant |
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Current Revision
| 1997 |
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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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Hardness is determined using a buret titration. The applicable range of this method is 0 - 25,000 mg/L as CaCO3. |
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Scope and Application
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This buret titration method is applicable to determining the hardness of water, wastewater, and seawater. |
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Applicable Concentration Range
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0 - 25000 mg/L |
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Interferences
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(1) The addition of one CDTA Magnesium Salt Powder Pillow will remove metals interferences at or below the following levels: Aluminum - 50mg/L; Cobalt - 200 mg/L; Copper - 100 mg/L; Iron - 100 mg/L; Manganese - 200 mg/L; Nickel - 400 mg/L; Zinc - 300 mg/L. Additional CDTA Magnesium Salt Powder Pillows may be required when more than one metal is present at or above these concentrations. (2) The results obtained with CDTA Magnesium Salt will include the hardness contributed by those soluble metal ions present. The mg/L of metal present multiplied by its calcium carbonate Hardness Equivalent Factor should be subtracted for each metal present from the total hardness determined in Step 8 of the procedure to obtain the hardness contributed by calcium and magnesium only. (3) Iron does not interfere up to 15 mg/L. Above this level it causes a red-orange to green end point which is sharp and usable up to 30 mg/L iron. Manganese titrates directly up to 20 mg/L but masks the end point above this level. (4) Copper and aluminum interfere at levels of 0.10 and 0.20 mg/L, respectively. Cobalt and Nickel interfere at all levels and must be absent or masked. Excess Potassium Cyanide has no effect on test results. (5) Barium, Strontium and Zinc titrate directly. Orthophosphate causes a slow end point and polyphosphate must be absent for accurate results to be obtained. Acidity and alkalinity at 10,000 mg/L (as CaCO3) do not interfere. Saturated sodium chloride solutions do not give a distinct end point but the titration can be run directly on sea water samples. (6) Highly buffered samples or extreme sample pH may exceed the buffering capacity of the reagents and require sample pretreatment per the procedure. |
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Quality Control Requirements
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Analysis of standards for accuracy check. |
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Sample Handling
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Collect samples in plastic or glass bottles. Preserve the sample with 1.5 mL of nitric acid per liter of sample. pH should be less than 2. Stored preserved samples up to 6 months at room temperature. |
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Maximum Holding Time
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6 months |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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