Complexometric titration

The Chelatometrie ( v. gr chele " crab claw " ), also called complexometry, is a method of analytical chemistry. It is used mostly for the quantitative determination of metals in aqueous solution by titration. It was developed in 1945 by Gerold Schwarzenbach. It is based on the formation of chelate complexes, Umschlingungskomplexen with polydentate ligand, metal ions and complexing agents.

The solution to be titrated is given to be an indicator. This shows the condition of a different color after binding to the metal ion. Since the indicator is only weakly bound to the metal ion, it is released upon addition of the chelating ligand, so that changes the color of the solution. It is often carried out in a buffer solution to keep the pH constant. Metal indicator and buffer may be combined in Indicator buffer tablets.

In trade, chelating agents, see for example, under the name complexone, Idranal or Titriplex, followed by a roman numeral.