Sampling Ca titration with EDTA

5 Anthropogenic use of groundwater 3.1.5.1 Sampling Ca titration with EDTA 

To determine the amount of calcium in a water sample, e.g. the titration with EDTA (ethylenediaminetetraacetate, C2H4N2(CH2COOH)4) can be used. First of all, NaOH is added to the sample to obtain a pH value of at least 12. Then, a color indicator is admixed and titration with EDTA performed until the color changes. In doing so, all Ca is converted to a Ca-EDTA complex and detected in this form. 

The amount of EDTA that has to be added until the color changes is unknown. Therefore, EDTA is added step by step and the titration is continued beyond the point of color change. The point of color change will be determined afterwards using the obtained graph. 

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