Complexation reactions are widely used in analytical chemistry.
One of the first uses of these reactions was for titrating cations, the major topic of this work.
A complexometric titration is the one of titrimetric methods in which the reaction between
the analyte and titrant involves the formation of a complex.
a successful analytical method must meet the following requirements:
(i)
the
reaction must be sufficiently fast;
(ii)
it
should lead stoichiometrically to a single product ML without any intermediate
reactions or by-products;
(iii)
there
should be a large increase in free energy (see Gibbs Energy), so that the
reaction is effectively complete, that is, the stability constant; Kf
must be large;
(iv)
the
ligand L must be readily available and give stable standard solutions;
(v)
there
must be some simple means of monitoring the course of the reaction, that is,
for following changes in the concentration [M] or [ML].
These conditions are generally met if L is the conjugate base of an aminopolycarboxylic acid such as ethylenediaminetetraacetic acid (EDTA), which is known to form very stable 1:1 complexes with a large number of metals.
The earliest examples of metal–ligand complexation titrations are Liebig’s determinations, in the 1850s, of cyanide and chloride using, respectively, Ag+ and Hg2+ as the titrant. Practical analytical applications of com¬plexation titrimetry were developed after the introduction of amino carboxylic acids as multi-dentate ligands by Schwarzenbach in 1945.
The earliest examples of metal–ligand complexation titrations are Liebig’s determinations, in the 1850s, of cyanide and chloride using, respectively, Ag+ and Hg2+ as the titrant. Practical analytical applications of com¬plexation titrimetry were developed after the introduction of amino carboxylic acids as multi-dentate ligands by Schwarzenbach in 1945.