This experiment was done to introduce young analysts to the use of electrochemical
instrumentation in analytical chemistry, specifically, potentiometric end-point detection.
The objective of the experiment is to analyse a mixed acid solution containing a strong
acid HCl and a weak acid CH3COOH. In the analysis of the solution by potentiometric
titration, it is possible to assess the appropriateness of the various end point detection
techniques – the Gran plot, the first derivative (δpH/δV) and the second derivative plot
Potentiometric titration involves the measurement of the potential of a suitable indicator
electrode as a function of titrant volume. The data provided by potentiometric titrations
are particularly more reliable than the data from titrations that use chemical indicators.
This is due to the fact that the procedure involves measuring and recording cell potential
(in pH) after each addition of reagent and the increments of addition shifting from large
to small as the end point is approached. The accuracy with which the end point can be
found by potentiometric titration depends upon the magnitude of the change in the
electromotive force (emf) in the region of the equivalence point. This depends upon the
concentration and strength of the reagents involved – acids and alkali in this case.