Determination of interfacial tension by drop weight method

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BACKGROUND

The stalagmometer is consist of a capillary bore with a bulb at the middle.1,2 The surface tension of the given liquid can be determined by using the following formula.


Where, v1=surface tension of test liquid

v2=surface tension of water

w1=weight of test liquid

w2=weight of water

Aim: To determine interfacial tension by using Oswalward stagmometerof two liquids.

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REQUIREMENTS

Chemicals: Water ,

Toluene

Apparatus: Ostwalds stagmometer

     Pipette

     Analytical balance

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PROCEDURE

The oswalds stagmometer was cleaned property and mounted on a suitable stand. Water was filled into the stalgmometer upto mark A. Dip the lower tip of the stalgmometer in toluene. Then the drops are allowed to fall by gravity. The no. of drops were counted when the liquid pass from mark A to B . The same procedure was repeated taking toluene in the stagmometere and dipping inside water. The no. of drops were recorded 3 times in order to obtain mean value by using the formula3.



Tabulation

Liquid Weight of Drops Surface tension(dyne/cm) Interfacial Tension(dyne/cm)
1 2 3 Mean
Water
Tolune

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CONCLUSION

Interfacial tension of toluene against water was found to be _ dyne/cm and water against toluene was found to be _ dyne/cm.

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REFERENCES

  1. More HN, Hajare AA. Practical Physical Pharmacy. Career Publications. 2010: 107-108.
  2. Gaud RS, Gupta GD. Practical Physical Pharmacy. CBS Publisher and Distributors. 2009: 65-67.
  3. Mohanta GP. Physical Pharmacy Practical Text, Pharma Book Syndicate. 2006: 34-35.