Q. Show the Colorimetric analysis?

Colorimetric analysis depends on the variation of the colour with the change in concentration of the compound. Usually, absorption of light is measured at different known concentrations of a compound and a graph is plotted between the absorption and concentration. Absorption of an unknown concentration of the compound is then measured and its concentration evaluated from the graph. Thus, 1 ,lo-phenanthroline or 2.2'-bipyridyl which forms coloured complexes with iron, are often used for its determination in fruits, wines, leather and other biological materials. There are many such reagents which are fruitfully employed for the quantitative determination of various metal ions.