What Does Du Nouy Ring Method Mean?
The Du Nouy ring method is used for measuring the interfacial tension between two liquids and the surface tension of a liquid. In force tensiometry, a probe is hung on a precise balance and brought into contact with the liquid interface to be tested. The probe will experience some forces as it interacts with the surface of the liquid, and can be used to calculate the surface tension.
The contact angle is controlled by complete wetting such that it is zero by using probes having surfaces with high energy such as platinum-iridium alloy.
The probes are of two types: the Wilhelmy plate and Du Nouy ring.
Trenchlesspedia Explains Du Nouy Ring Method
In the Du Nouy ring method, the maximum pull on a platinum ring attached to a balance is measured. The wetted length of the platinum ring is known and the measurement is converted into a surface tension value. The platinum ring hanging parallel to the liquid is allowed to sink into the liquid. The ring is then pulled in the vertical direction and drawn apart from the surface.
The surface tension of the liquid membrane hanging from the ring when it is withdrawn generates a force on the ring. As the ring is withdrawn further, the force changes. By using the maximum value of the force generated, the surface tension is calculated using the formula:
γ = (F / 4πR) C, where
- γ is the surface tension.
- F is the force acting on the platinum ring.
- R is the diameter of the ring.
- C is the correction factor.