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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 .
When a glass electrode is used to obtain the measurements on which the calculated equilibrium constants depend, the precision of the calculated parameters is limited by secondary effects such as variation of liquid junction potentials in the electrode. In practice it is virtually impossible to obtain a precision for log β better than ±0.001.
A metre bridge is a simple type of potentiometer which may be used in school science laboratories to demonstrate the principle of resistance measurement by potentiometric means. A resistance wire is laid along the length of a metre rule and contact with the wire is made through a galvanometer by a slider. When the galvanometer reads zero, the ...
They comprise a simple electronic amplifier and a pair of electrodes, or alternatively a combination electrode, and some form of display calibrated in pH units. It usually has a glass electrode and a reference electrode, or a combination electrode. The electrodes, or probes, are inserted into the solution to be tested.
The connection can be direct, through a narrow tube to reduce mixing, or through a salt bridge, depending on the other electrode and solution. This creates an ionically conductive path to the working electrode of interest. A reference electrode is an electrode that has a stable and well-known electrode potential.
Some commercially available reference electrodes have an internal junction which minimizes the liquid junction potential between the sample solution and the electrolyte in the reference electrode (KCl). The internal electrolyte is at fixed composition and the electrode response is given by the Nernst equation: E = E 0 − RT/F ln a F −, where: