Complexometric Titration
A titration based on the formation of a stable complex between the analyte metal ion and a chelating titrant.
Formula / equation
M²⁺ + EDTA⁴⁻ → [M(EDTA)]²⁻
Unit
mol/L
In depth
EDTA binds almost every metal ion in a clean 1:1 ratio, which makes the stoichiometry simple. Because the stability of the complex depends on pH, a buffer is essential, and selectivity is achieved by adjusting pH or by adding masking agents.
Examples in the real world
Determining total water hardness by titrating calcium and magnesium with EDTA against eriochrome black T.