Complexometric titration:

Complexometric titration using ethylene diamine tetracetate ions (HY^3-) produced at a mercury cathode have been developed within the titration of served cations. Reduction of the ammonium mercury (II) EDTA chelate at a mercury cathode was used to generate [HY^3-] ions.

HgNH₃Y^2- + N H₄⁺ + 2e → Hg + 2NH₃ + HY^3- (at mercury cathode)

Because mercury chelate is much stable than the corresponding metal complexes of Zinc, calcium, lead or copper, titration of these cations are probable through this method.