Complexometric titrations are a type of volumetric analysis in which the analyte forms a stable complex with a titrant, usually a metal ion with a chelating agent. They are mainly used to determine metal ions in a solution.
Principle:
- Based on the formation of a coordination complex between a metal ion (analyte) and a ligand (titrant).
- The reaction is stoichiometric, so the amount of metal can be calculated from the volume of titrant used.
- The end point is detected by a suitable indicator that changes color when all metal ions have reacted.
Procedure:
- Prepare the analyte solution containing the metal ions.
- Add the complexing agent (titrant) gradually to the solution.
- Use a metal ion indicator that changes color when all metal ions have formed complexes.
- Measure the volume of titrant used and calculate the concentration of the metal ions.
Common Titrants and Indicators:
- Titrant: EDTA (ethylenediaminetetraacetic acid)
- Indicators: Eriochrome Black T, Murexide, Calmagite
Applications:
- Determining hardness of water (calcium and magnesium ions).
- Estimating metal ions in ores, alloys, and industrial products.
- Analysis in pharmaceuticals and environmental chemistry.
Advantages:
- Highly specific for metal ions.
- Can be used for mixtures of metals with proper indicators.