Question

What are the applications of adsorption in chemical analysis?

Answer 1

Adsorption has the following applications in chemical analysis:

(i) In qualitative analysis: Certain qualitative tests such as the lake test for the confirmation of \[\ce{Al^{3+}}\] ions are based upon adsorption, i.e., \[\ce{Al(OH)3}\] has the capacity to adsorb the colour of blue litmus from the solution.

(ii) In adsorption indicators: Many adsorption indicators are being used in volumetric analysis e.g., dyes such as eosin and fluorescein are used as adsorption indicators. In these methods, the dyes are adsorbed on the surfaces of certain precipitates (such as silver halides) which give characteristic colour at the end point.

(iii) In ion-exchange resins: The organic polymers containing groups like \[\ce{-COOH, -SO3H}\] and \[\ce{-NH2}\], etc. possess the property of selective adsorption of ions from solutions. These are quite useful in the softening of water.

(iv) Separation of inert gases: Due to the difference in degree of adsorption of gases by charcoal, a mixture of noble gases can be separated by adsorption on coconut charcoal at different temperatures.

(v) In froth floatation process: A low grade sulphide ore is concentrated by separating it from silica and other earthly matter by adsorption using pine oil and frothing agent.

(vi) Chromatographic analysis: The chromatographic technique for purification used in analytical and industrial fields is based on the phenomenon of adsorption.