Surface and Interfacial tension [Part-3(b)]�(Measurement of Surface and Interfacial tension: 3. Wilhelmy plate method 4. DuNouy ring method )�

MEASUREMENT OF SURFACE AND INTERFACIAL TENSION
Wilhelmy Plate Methods: The DuNouy Ring Method.

1. IIIrd Semesester B. pharmacy Physical Pharmaceutics-I Unit-III Surface and Interfacial tension [Part-3(b)] ( Measurement of Surface and Interfacial tension: 3. Wilhelmy plate method 4. DuNouy ring method ) Miss. Pooja D. Bhandare (Assistant professor) Kandhar college of pharmacy

2. MEASUREMENT OF SURFACE AND INTERFACIAL TENSION Capillary Rise Method. Drop Count and Weight Method. Wilhelmy Plate Methods The DuNouy Ring Method.

3. 3. Wilhelmy plate method The apparatus consist of a thin mica, glass or platinum plate attached to a suitable balance. When used as a detachment method, the plate is immersed in the liquid, and the liquid container is gradually lowered. The reading on the balance immediately prior to detachment is noted.

4. Immersion of the plate into the lower of two liquids in a container and subsequent detachment will give the interfacial tension.

5. The detachment force is equal to the surface tension multiplied by the perimeter of the surface detached. WL – W = 2 (L+T) γ On rearrangement, γ = (WL – W)/ 2 (L + T) Where, WL= reading on the balance prior to detachment W = weight of plate L = length of plate T= thickness of plate

6. 4 . The DuNouy Ring Determination Method Suitable for measuring surface and interfacial tensions. Apparatus: DuNouy tensiometer or torsion balance. Principle: Force necessary to detach a platinum- iridium ring immersed at the surface or interface is proportional to the surface or interfacial tension. The force required to detach the ring in this manner is provided by a torsion wire and is recorded in dynes on calibrated dial.

7. Detachment force is equal to surface tension multiplied by perimeter of liquid detached. Hence, P = W = 2 п ( + ) γ On rearrangement, γ = Where, P = pull exerted through torsion wire. W = Force in terms of weight = inner and outer radius of disk  

8. Thank you!