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In surface science, a tensiometer is a measuring instrument used to measure the surface tension (γ) of liquids or surfaces.Tensiometers are used in research and development laboratories to determine the surface tension of liquids like coatings, lacquers or adhesives.
Surface tension is an important factor in the phenomenon of capillarity. Surface tension has the dimension of force per unit length, or of energy per unit area. [4] The two are equivalent, but when referring to energy per unit of area, it is common to use the term surface energy, which is a more general term in the sense that it applies also to ...
'drop') is one of the most common methods for measuring surface tension. The principle is to measure the weight of drops of a fluid of interest falling from a capillary glass tube, and thereby calculate the surface tension of the fluid. We can determine the weight of the falling drops by counting them. From it we can determine the surface tension.
The measurement is performed with a force tensiometer, which typically uses an electrobalance to measure the excess force caused by the liquid being pulled up and automatically calculates and displays the surface tension corresponding to the force. Earlier, torsion wire balances were commonly used.
(σ: surface tension, ΔP max: maximum pressure drop, R cap: radius of capillary) Later, after the maximum pressure, the pressure of the bubble decreases and the radius of the bubble increases until the bubble is detached from the end of a capillary and a new cycle begins. This is not relevant to determine the surface tension. [3]
An approximate theory was developed by Bernard Vonnegut [3] in 1942 to measure the surface tension of the fluids, which is based on the principle that the interfacial tension and centrifugal forces are balanced at mechanical equilibrium. This theory assumes that the droplet's length L is much greater than its radius R, so that it may be ...
The most common way to measure surface energy is through contact angle experiments. [1] In this method, the contact angle of the surface is measured with several liquids, usually water and diiodomethane. Based on the contact angle results and knowing the surface tension of the liquids, the surface energy can be calculated. In practice, this ...
The magnitude of the capillary force on the plate is proportional to the wetted perimeter, = +, and to the surface tension of the liquid-air interface. A Wilhelmy plate is a thin plate that is used to measure equilibrium surface or interfacial tension at an air–liquid or liquid–liquid interface.
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