Determination of surface tension by Stallagmometer method (drop method)
There are several methods of surface tension measurements:
1. Capillary rise method
2. Stallagmometer method - drop weight method
3. Wilhelmy plate or ring method
4. Maximum bulk pressure method.
5. Methods analyzing shape of the hanging liquid drop or gas bubble.
6. Dynamic methods.
Experimental procedure
1. Fill the stalagmometer up to the top mark with distilled water.
2. Release the water to the beaker and count how many drops it takes to decrease the water level in stalagmometer down to the bottom mark.
3. Write down the number of drops (n2) of water .
4. Empty and dry the weighing bottle and stalagmometer, and prepare it for the next measurement.
5. Repeat the procedure 1-4 for another two time with water.
6. Repeat steps 1 - 4 for liquids with the unknown surface tension.
7. Write down the densities of studied liquids according to the notes on bottles, and density of distilled water at the actual laboratory temperature from the reference table.
8. Using equation
surface tension 1= surface tension 2 (No. of Drops 2 * Density 1/ No. of Drops 1 * Density 2), calculate the surface tension for all the studied liquids.