Surface tension with the ring method (Du Nouy method)
Principle
The force is measured on a ring shortly before a liquid film tears using a torsion meter. The surface tension is calculated from the diameter of the ring and the tear-off force.
Benefits
- High sensitivity measurement possible thanks to ring method
- Analogue set-up that can also be used as a demo experiment in the lecture hall
- Torsion dynamometer used can measure very small forces and is therefore suitable to measure other electrostatic and magnetic interactions between bodies
- Interdisciplinary use also in applied sciences or physical chemistry
Surface tension measuring ring
Ethyl alcohol, absolute 500
Olive oil,pure 100
Water, distilled 5 l
Volumetric pipette, 10 ml
Volumetric pipette, 20 ml
Pipette dish
Pipettor
Graduated cylinder 100 ml
Glass tubes,straight, 150 mm, 10
Stopcock,1-way,straight, glass
Retort stand, h = 750 mm
Right angle boss-head clamp
Universal clamp
Silicone tubing i.d. 7mm, 1 m
Cristallizing dish,boro3.3, 500ml
Crystallizing dish, boro3.3, 900ml
Magnetic stirring bar 30 mm, cylindrical
Supp.rod stainl.st.,50cm,M10-thr.
Silk thread, l = 200 m
Torsion dynamometer, 0.01 N
Magnetic stirrer with heater MRHei-Tec
Right angle clamp expert
Tasks
- Determine the surface tension of olive oil as a function of temperature.
- Determine the surface tension of water/methanol mixtures as functions of the mixture ratio.
What you can learn about
- Surface energy
- Interface
- Surface tension
- Adhesion
- Critical point
- Eötvös equation