Examples of such reagents include EDTA, DMG
(dimethylglyoxime), a–nitroso–b–naphthol, cupron, etc •
Hardness of water is estimated by simple titration with Na2EDTA The Ca
2+ and Mg
2+ ions form stable complexes with EDTA The
selective estimation of these ions can be done due to difference in
the stability constants of calcium and magnesium complexes