Thermometric titrimetry Theorical foundations and applications

This article presents the fundamental characteristics of thermometric titrimetry, an isoperibolic titration method whose general principle consists in monitoring a titration reaction by means of the temperature variation of the reaction mixture as the titrant solution is added.

Thermometric titration has a number of possibilities:

• analytically: this is a linear method indicating the end of the reaction;

• in physico-chemical terms, it enables direct measurement of thermal effects of various origins, in particular those due to the titration reaction.

From a practical point of view, the use of thermistors as devices for monitoring the evolution of a process (semiconductors insensitive to the nature of the medium in contact with them, whether aqueous, non-aqueous or multi-phase) offers a clear advantage over that of electrodes, for example, whose use requires a conductive medium.

Thermometric titrimetry belongs to the group of thermal methods or thermoanalytical and enthalpimetric methods which, according to the IUPAC "International Union for Pure and Applied Chemistry" and the ICTAC "International Conference for Thermal Analysis and Calorimetry", cover two groups of analytical methods:

• thermal analysis - methods in which a chemical property of the substance under study (dehydration, oxidation, decomposition, desolvation, etc.) or a physical process involving it (melting, crystallization, heat capacity, glass transition or solid-solid transition) is measured as a function of its temperature, which is varied in a programmed way. There are several methods of this type. These include thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC);

• enthalpimetric analysis: methods in which the enthalpy variation accompanying a reaction of the substance under study is measured directly or indirectly during a quantitative determination. Thermometric titrimetry falls into this group.

A summary of the analytical and calorimetric possibilities of thermometric titrimetry is presented here. It is based on some particularly illustrative examples.