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.