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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 ...
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
An ion-selective electrode (ISE), also known as a specific ion electrode (SIE), is a simple membrane-based potentiometric device which measures the activity of ions in solution. [1] It is a transducer (or sensor ) that converts the change in the concentration of a specific ion dissolved in a solution into an electrical potential .
The Gran plot is based on the Nernst equation which can be written as = + {+} where E is a measured electrode potential, E 0 is a standard electrode potential, s is the slope, ideally equal to RT/nF, and {H +} is the activity of the hydrogen ion.
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 design of the electrodes is the key part: These are rod-like structures usually made of glass, with a bulb containing the sensor at the bottom. The glass electrode for measuring the pH has a glass bulb specifically designed to be selective to hydrogen-ion concentration.
A potentiometer being calibrated and then measuring an unknown voltage. R 1 is the resistance of the entire resistance wire. The arrow head represents the moving wiper.. In this circuit, the ends of a uniform resistance wire R 1 are connected to a regulated DC supply V S for use as a voltage divider.
A redox indicator (also called an oxidation-reduction indicator) is an indicator which undergoes a definite color change at a specific electrode potential. The requirement for fast and reversible color change means that the oxidation-reduction equilibrium for an indicator redox system needs to be established very quickly. Therefore, only a few ...