A titrimetric method involves the controlled reaction of a standard reagent in known amounts with a
solution of the analyte, in order that the stoichiometric or equivalence point for the reaction between the
reagent and the analyte may be located. If the details of the reaction are known and the stoichiometric
point is located accurately and precisely, the amount of analyte present may be calculated from the
known quantity of standard reagent consumed in the reaction. In most cases a standard reagent solution
is prepared and added manually or automatically from a burette; an alternative procedure is coulometric
generation of the reagent in situ. The stoichiometric point may be detected by use of a visual indicator
or by an electrochemical method (Chapter 6).
Definitions
Titration
The overall procedure for the determination of the stoichiometric or equivalence point.
Titrant
The solution added or reagent generated in a titration.
Titrand
The solution to which the titrant is added.
End Point
A point in the progress of the reaction which may be precisely located and which can be related to the
stoichiometric or equivalence point of the reaction; ideally, the two should be coincident.
Indicator
A reagent or device used to indicate when the end point has been reached.
Titrimetric Reactions
It is clear that reactions suitable for use in titrimetric procedures must be stoichiometric and must be fast
if a titration is to be carried out smoothly and quickly. Generally speaking, ionic reactions do proceed
rapidly and present few problems. On the other hand, reactions involving covalent bond formation or
rupture are frequently much slower and a variety of practical procedures are used to overcome this
difficulty. The most obvious ways of driving a reaction to completion quickly are to heat the solution,
to use a catalyst, or to add an excess of the reagent. In the last case, a back titration of the excess
reagent will be used to locate the stoichiometric point for the primary reaction. Reactions employed in
titrimetry may be classified as acid-base; oxidation-reduction; complexation; substitution; precipitation.