Analysis of a spring water

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Determination of Cl- ions: complexometric/colorimetric titration with Hg2+


Dosing principle

In the presence of chloride ions, mercuric salts create soluble complexes sparsely ionised:

Hg2+ + 2 Cl- → HgCl2

An excess of mercuric ions is detected by means of a colored indicator (diphenyl carbazone) that takes on a purple color with Hg2+ in a diluted acid environment (pH 2.8 to 3).

0.5 mg of Cl- ⇔ 1 mL of Hg2+ at 0.0142 N

The presence of phosphates, nitrates or sulfates does not interfere with this analysis, even at high concentrations.

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