Surface Tension

Surface tension is a measure of the cohesive energy of a liquid. It is the excess free energy at the interface of contact between two fluids. When one fluid is a gas the tension is termed surface tension, when both fluids are liquids it is termed interfacial tension. It is expressed in units of milliNewtons/meter (mN/m) or dynes/centimeter. It is useful in analyzing fluids re foaming, spreading, emulsification, washability and other fluid characteristics.   For more on theory click this link.

Methods of measurement

Tensiometry

A reservoir of liquid is brought into contact with a probe (Wilhelmy plate, DuNouy ring, rod) hanging on a sensitive force balance. Surface tension is calculated from the force on the balance.                                

  For more on theory click this link.

Instruments which use tensiometry to measure surface tension:

Sigma 70 the finest tensiometer available. Fiber range microbalance accurate to 1 microgram. DuNouy ring, Wilhelmy plate and custom probe experiments included in expansive software package.

Sigma 701computer controlled research quality tensiometer. Measure with DuNouy ring, Wilhelmy plate or custom probe. Modular construction allows upgrade to Sigma 70 capabilities. Accurate to 0.01 mN/m.

Sigma 703 a simple, reliable instrument for measurement of surface and interfacial tension by DuNouy ring and Wilhelmy plate methods. Ideal for quality control, basic research and educational stteings. Accurate to 0.1 mN/m.

Pendant Drop Shape Analysis

A drop of liquid is extruded from a syringe tip. An image of the drop is captured. Analysis of the shape of the drop is used to calculate surface tension.           For more on theory click this link.

Instruments which use pendant drop shape analysis to measure surface tension:

CAM 200 research quality computerized goniometer. Strobed monochromatic LED light source, telecentric optics and high speed camera yield exceptional quality images. Data reduction software includes profile fitting to Young-Laplace equation for most accurate surface tension measurements available.

 CAM100 low-priced goniometer with computer assisted data reduction. Uses 50mm USB camera and LED lighting. Get the power of sophisticated computer image analysis in an economical package.

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