2. Complexometric Titration
Complexometric titration is a form of volumetric
analysis in which the formation of a colored complex is
used to indicate the end of a titration . It is useful for
the determination of a mixture of different metal ions
in solution.
4. Occurance of complexometric
titration
Metal ions in solution are always solvent that is a
definite number of solvent molecules are firmly bound
to the metal ions .However, these bound molecules are
replaced by other molecules or ions during the
formation of a metal complex or coordination
compound.
5. Complexometric titration is an
acid base titration
The reaction between metal ion and complexing ions
is called complexation reaction . Ligands or
complexing agents can be any electron donating which
has the ability to bind with metal ion producing a
complex ion. Such ligand are lewis bases.
6. Reaction for complexing titration
The reaction reaches equilibrium rapidly after each
portion of titrant is added.
Interfering situation do not arise for instance the
stepwise formation of several different complexes of
the metal ion with the titrant.
A complexometric indicator capable of locating
equivalence point with fair accuracy is available.
8. Ligand and classification
Molecules or ions which displace solvent molecules
from the metal binding compound are called ligands.
They are mainly two types:
1. Unidentate.
2. Multidentate.
Multidentate are classified into four types:
>Bidentate >Tridentate
>Quardridentate >Hexadentate
9. Stability of complexes
Complexation is also an equilibrium process which
can therefore be defined by the law of mass action. A
complex is formed by the reaction .
10. Titration curves
In the EDTA titration the negative logarithm of the
free metal ion concentration is plotted against the
volume of EDTA solution
11. Chelating effect
Chelating agent usually form metal complexes that are
normally more stable than the complexes formed by
unidentate ligands. The difference between them is
commonly referred as chelaing effect.
13. General properties of metal ion
indicator
Indicator must produce sharp end point.
The color reaction should be specific.
The metal indicator complex must be less stable than
the metal EDTA complex.
The color difference between free indicator and metal
indicator should be distinct.
14. Conclusion
Complexometric titration has made it possible for
man to be exposed to an advanced method of titration
which not only enables us to analyze more ions , but
also do them in very small quantities.
