TH 10Titration / Drop Count Test for Total Hardness 1 drop = 10 mg/L CaCO3 |
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| Product Code | 600400 |
| Contents | Buffer/Indicator, 15 mL Titration Solution, 15 mL Test Tube, 10 mL Instructions for Use |
| Analytical Method | Complexometric Titration: At pH = 10, earthalkali metals (calcium, magnesium and strontium) form a pink coloured complex with certain indicator dyes (e.g. eriochrome black T, calmagite). On adding EDTA (ethylenediamine tetraacetic acid), these metals prefer to complex with EDTA, and release the indicator dye. As the uncomplexed dye exhibits a blue colour, the titration endpoint is indicated by a sudden colour change from pink to pure blue. The amount of EDTA added is directly proportional to the concentration of Ca2+, Mg2+ and Sr2+ ions. Results are expressed as calcium carbonate CaCO3. |
| Number of Tests | 50 – 80 (depending on total hardness level) |
| Interferences | Other metals like Al, Fe, Mn or Cu interfere by complexing the indicator dye and not releasing it any more. The indicator becomes "blocked" and a colour change at the titration endpoint does not occur. The concentration of these interfering metals should be kept below 1 mg/L. Sample dilution may be required in order to achieve this. |
| Measuring Range | The recommended measuring range is 10 to 200 mg/L (1 – 20 drops @ 10 mg/L) for 5 mL of sample volume. This range can be extended by taking a smaller or larger water sample. For a 2.5 mL sample the measuring range is 20 to 400 mg/L and for a 10 mL sample the range is 5 to 100 mg/L. |
| Shelf Life | 2 years |
| Applications | Determination and monitoring of total hardness in industrial water treatment (boiler feed water), water softening, drinking water, ground water, irrigation. |