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The most common application of ion-selective glass electrodes is for the measurement of pH. The pH electrode is an example of a glass electrode that is sensitive to hydrogen ions. Glass electrodes play an important part in the instrumentation for chemical analysis, and physicochemical studies.
Potentiometry passively measures the potential of a solution between two electrodes, affecting the solution very little in the process. One electrode is called the reference electrode and has a constant potential, while the other one is an indicator electrode whose potential changes with the sample's composition. Therefore, the difference in ...
A platinum wire electrode is immersed in a saturated aqueous solution of quinhydrone, in which there is the following equilibrium C 6 H 6 O 2 ⇌ C 6 H 4 O 2 + 2H + +2e −. The potential difference between the platinum electrode and a reference electrode is dependent on the activity, +, of hydrogen ions in the solution.
The electrode potential is proportional to pH when pH is defined in terms of activity. The precise measurement of pH is presented in International Standard ISO 31-8 as follows: [ 15 ] A galvanic cell is set up to measure the electromotive force (e.m.f.) between a reference electrode and an electrode sensitive to the hydrogen ion activity when ...
To measure the pH of a solution, the electrodes are used as probes, which are dipped into the test solutions and held there sufficiently long for the hydrogen ions in the test solution to equilibrate with the ions on the surface of the bulb on the glass electrode. This equilibration provides a stable pH measurement.
The antimony electrode has been investigated for its ability to function as a pH electrode. [1] The electrode is made of elemental antimony. The electrochemical process can be formulated as Sb 2 O 3 (s) + 6 H + + 6 e − ⇌ 2Sb(s) + 3H 2 O. The oxide, Sb 2 O 3, is present on the surface of the electrode. Although this electrode does not give ...
Reference electrodes generally used are hydrogen electrodes, calomel electrodes, and silver chloride electrodes. The indicator electrode forms an electrochemical half-cell with the interested ions in the test solution. The reference electrode forms the other half-cell. The overall electric potential is calculated as
A silver chloride electrode is a type of reference electrode, commonly used in electrochemical measurements. For environmental reasons it has widely replaced the saturated calomel electrode. For example, it is usually the internal reference electrode in pH meters and it is often used as reference in reduction potential measurements.