Electrocapillarity
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If an
electric field An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) descri ...
is applied parallel to the surface of a liquid and this surface has a net charge then the surface and so the liquid will move in response to the field. This is electrocapillary flow, an example of electrocapillarity. Electrocapillary phenomena are phenomena related to changes in the surface free energy (or interfacial tension) of charged fluid interfaces, for example that of the dropping mercury electrode (DME), or in principle, any electrode, as the
electrode potential An electrode is an electrical conductor used to make contact with a nonmetallic part of a Electronic circuit, circuit (e.g. a semiconductor, an electrolyte, a vacuum or a gas). In electrochemical cells, electrodes are essential parts that can c ...
changes or the electrolytic solution composition and concentration change. The term electrocapillary is used to describe the change in mercury (Hg)
electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or a gas). In electrochemical cells, electrodes are essential parts that can consist of a varie ...
potential as a function of the change in the surface or interfacial tension of the Hg determined by the capillary rise method. The phenomena are the historic main contributions for understanding and validating the models of the structure of the electrical double layer. The phenomena are related to the electrokinetic phenomena and consequently to the
colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others exte ...
chemistry.


Interfacial tension

The interfacial (surface) tension, St, (dyne cm−1), can be calculated by applying the equation of capillary rise method (when the contact angle Ө → 0):
St = \frac where: * h (cm) is the height of Hg column above the Hg meniscus in the capillary * r (cm) is the
radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...
of capillary * g is the
acceleration In mechanics, acceleration is the Rate (mathematics), rate of change of the velocity of an object with respect to time. Acceleration is one of several components of kinematics, the study of motion. Accelerations are Euclidean vector, vector ...
due to
gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...
* d (g cm−3) is the Hg
density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...
The circuit contains Hg electrode as the ideally polarizable electrode and a reference electrode as the non-polarizable electrode. Thus, when an external voltage is applied, only EM/S of Hg/solution fluid interface is changed.


See also

* Colloid chemistry *
Electrical double layer Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwel ...
* Electrokinetic phenomena * Liquid metal electrode * Rotating disk electrode


References

* Modern Electrochemistry, Volume 2, J.O'M. Bockris and A.K.N. Reddy, Plenum/Rosetta Edition, 2000. * Theoretical Electrochemistry, L.I. Antropov, English Edition, Mir Publishers, Moscow. Electrochemistry {{Electrochem-stub