Du Noüy Ring Tensiometer

Du Noüy Ring Tensiometer is the instrument for weight-based measurement of interfacial tension [1]. The technique involves slow lifting of the ring made of platinum-iridium from the surface of a liquid. As this ring is hung on an electrobalance and brought into contact at the interface, the maximum force caused by the liquid being pulled up can be used to calculate the surface tension. The critical micelle concentration (CMC) can be determined by this technique through measuring the surface tension at various surfactant concentrations. Below the CMC, the surface tension decreases with increasing concentration because more surfactant molecules adsorb at the surface. Above the CMC, further adding of surfactant serves only to form micelles and the surface tension stays constant.

Typical measurements:

For surface tension measurement; solution with low to moderate viscosity 

• 1.5 – 2 ml for small ring
• 5-20 ml for large ring

For CMC measurement; surfactant solution > 30 ml

Equipment:

Dynamic contact angle meter and tensiometer DataPhysics DCAT serie 11 and 21.

References:

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[1]  https://www.dataphysics-instruments.com/products/dcat/ (Accessed on 27 Nov 2021)

 

Contact:

Dr. Waraporn Wichaita ( 06131-379-723)

Dr. Lucas Caire da Silva ( 06131-379-581)