Tensiometer
Encyclopedia
A Tensiometer as it applies to physics is an instrument used to measure the surface tension
(
) of liquids.
/Tensiometer to measure the surface tension
and interfacial tension of a liquid using the pendant or sessile drop methods. It is a more difficult experimental measurement to accomplish and is not nearly as accurate as the Wilhelmy plate method described below. A drop is produced and the profile is then captured using a goniometer/tensiometer. The software then analyses the profile of the drop and makes a series of calculations. With pendant drops, in older, more obsolete software, the maximum diameter and the ratio between this parameter and the diameter at the distance of the maximum diameter from the drop apex is evaluated and formulas are used to derive on the basis of the Young-Laplace equation surface tension. In more current, more accurate software, the LaPlace equation itself is used to calculate surface tension for hundreds of pairs of data points along the profile of the drop. Sophisticated software routines automate this computationally intensive process.
Wilhelmy Plate Tensiometer
The Wilhelmy Plate tensiometer requires a plate to make contact with the liquid surface. It is widely considered the simplest and most accurate method for surface tension measurement.
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
(
) of liquids.Goniometer/Tensiometer
Surface scientists sometimes use a GoniometerGoniometer
A goniometer is an instrument that either measures an angle or allows an object to be rotated to a precise angular position. The term goniometry is derived from two Greek words, gōnia, meaning angle, and metron, meaning measure....
/Tensiometer to measure the surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
and interfacial tension of a liquid using the pendant or sessile drop methods. It is a more difficult experimental measurement to accomplish and is not nearly as accurate as the Wilhelmy plate method described below. A drop is produced and the profile is then captured using a goniometer/tensiometer. The software then analyses the profile of the drop and makes a series of calculations. With pendant drops, in older, more obsolete software, the maximum diameter and the ratio between this parameter and the diameter at the distance of the maximum diameter from the drop apex is evaluated and formulas are used to derive on the basis of the Young-Laplace equation surface tension. In more current, more accurate software, the LaPlace equation itself is used to calculate surface tension for hundreds of pairs of data points along the profile of the drop. Sophisticated software routines automate this computationally intensive process.
Du Noüy-Padday method
This method uses a rod which is lowered into a test liquid. The rod is then pulled out of the liquid and the force required to pull the rod is precisely measured. This is a rather novel method which is accurate and repeatable. The Du Noüy-Padday Rod Pull Tensiometer will take measurements quickly and unlike the ring and plate methods, will work with liquids with a wide range of viscosities.Du Noüy Ring Tensiometer
This type of tensiometer uses a platinum ring which is submersed in a liquid. As the ring is pulled out of the liquid, the tension required is precisely measured in order to determine the surface tension of the liquid. This method requires that the platinum ring be nearly perfect; even a small blemish or scratch can greatly alter the accuracy of the results. A correction for buoyancy must be made. This method is considered inaccurate compared to the plate method but is still widely used for interfacial tension measurement between two liquids.Wilhelmy Plate TensiometerWilhelmy plateA Wilhelmy plate is a thin plate that is used to measure equilibrium surface or interfacial tension at an air–liquid or liquid–liquid interface. In this method, the plate is oriented perpendicular to the interface, and the force exerted on it is measured...
The Wilhelmy Plate tensiometer requires a plate to make contact with the liquid surface. It is widely considered the simplest and most accurate method for surface tension measurement.See also
- Surface tensionSurface tensionSurface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
- Young-Laplace equation
- Capillary actionCapillary actionCapillary action, or capilarity, is the ability of a liquid to flow against gravity where liquid spontanously rise in a narrow space such as between the hair of a paint-brush, in a thin tube, or in porous material such as paper or in some non-porous material such as liquified carbon fiber, or in a...
- PiezometerPiezometerA piezometer is either a device used to measure static liquid pressure in a system by measuring the height to which a column of the liquid rises against gravity, or a device which measures the pressure of groundwater at a specific point...
- Pierre Lecomte du NouyPierre Lecomte du NoüyPierre Lecomte du Noüy was a French biophysicist and philosopher. He probably is best-remembered by scientists for his work on the surface tension, and other properties, of liquids.- Life and work :...