Applications of Potentiometry in Non-Aqueous Solutions

Potentiometry and potentiometric titrations are widely used in studying various types of reactions and equilibria in non-aqueous systems (Sections 6.3.1-6.3.4). They also provide a convenient method of solvent characterization (Section 6.3.5). Moreover, if the electrode potentials in different solvents can accurately be compared, potentiometry is a powerful method of studying ion solvation (Section 6.3.6). 

---

Experiments are under way for the production of ion-selective membrane electrodes that can also be used in non-aqueous solutions, and studies are being made of the possibilities of application of liquid junction-free potentiometry in non-aqueous solutions. High-performance computer evaluation procedures permit the employment of spectrophotometric equilibrium measurements in the study of complex systems. Spectrophotometric measurements are not prone to greater errors in non-aqueous solutions than in water. 

Just as in aqueous solutions, potentiometry is the most fundamental and powerful method of measuring pH, ionic activities and redox potentials in non-aqueous solutions. Here we deal with the basic techniques of potentiometry in non-aque-ous solutions and then discuss how potentiometry is applicable to studies of chemistry in noil-aqueous solutions. Some topics in this field have been reviewed in Ref. [1],... 

When three-electrode devices are used, reference electrodes similar to those in potentiometry (Section 6.1.2) are applicable, because no appreciable current flows through them. The reference electrodes used in non-aqueous solutions can be classified into two groups [1, 2, 5, 10]. Reference electrodes of the first group are prepared by using the solvent under study and those of the second group are... 

Because of the es erimental difficulties associated with molten salts, it is to be expected that the application of electroanalytical techniques lagged behind the corresponding application to aqueous and even non-aqueous solutions. Potentiometry was the earliest electroanalytical technique applied to molten salts, no doubt because it presented no special problems outside of thermoelectric effects. Interestingly, the scope of potentiometry in high tempera-... 

For the study of the solvent effect, comparable equilibrium constants have to be determined in water and in solution made with non-aqueous solvents or solvent mixtures. Potentiometric (usually pH-metric) equilibrium measurements are used for this purpose in polyfunctional systems. The solvent effect makes the application of potentiometry somewhat difficult. The substitution of water by organic solvents results in changes of the autoprotolysis constant of the solvent changing the pH scale. The lower relative permittivity of the system favours association processes which have to be considered, e.g., in the determination of the ionic strength of the solution. Diffusion potentials at the liquid junctions connecting the galvanic cell with the reference electrode may falsify the measured data. 

---