Q. Show Applications of coordination compounds?

Innumerable applications of coordination compounds in fields as divergent as biology,  industry. Agriculture, analytical chemistry makes it impossible to cite them all at one place. A few selected examples are given below to indicate their application to different fields. Let us first consider the role which the complexes play in gravimetric, volumetric, colorimetric analysis.

A selective precipitation of Fe(III), Al(II1) or Cr(II1) with amonia takes place keeping Ag(I), Cu(II), Ni(II), Co(II), MnCII) and Zn(I1) in solution as soluble ammine complexes.

From a mixture of Fe(III), Cu(II), Pb(II), Bi(II1) and Ag(I), only Ag(1) ion can be  precipitated as iodide, all other ions can be made to remain in solution by previous addition  of EDTA (ethylenediamine tetraacetate ion) to the solution.

The EDTA complexes of some metal ions are stable even to hydrogen sulphide. For example, in the presence of EDTA, Pb(I1) is not precipitated as sulphide from weakly acidic  solutions; Ni(II), Co(II), Mn(I1) and Zn(I1) which are normally precipitated as sulphides in  ammonical solution would also not give any precipitate.

The EDTA is one of the most important reagents now used in volumetric analysis. Since the estimation of various cations using EDTA is largely pH dependent, EDTA is also used as  masking or damasking agent in titration of mixture of cations.