EDTA is used in the estimation of :

A chemical compound called ethylenediaminetetraacetic acid (edta) can form edta-metal complexes with a variety of metal ions, but not with alkali metal ions like ${\mathrm{Na}}^{+}$ and${\mathrm{K}}^{+}$. It creates stable complexes with the alkaline earth metal ions ${\mathrm{Ca}}^{2+}$ and ${\mathrm{Mg}}^{2+}$ in alkaline circumstances (pH9). The total amount of ${\mathrm{Ca}}^{2+}$ and ${\mathrm{Mg}}^{2+}$ ions that are dissolved in a water sample can be determined using the edta reagent. As a result, titration with a standard edta solution can be used to assess the overall hardness of a water sample.