Understanding the Wilhelmy Plate Method for Calculating Surface Tension

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The discussion centers on the Wilhelmy plate method for calculating surface tension, highlighting a discrepancy between two formulae regarding the division of the surface tension force by the perimeter of the plate. One formula uses the perimeter directly, while the other divides by twice the perimeter. Participants question why the perimeter is used instead of just the length of the plate, considering that the liquid does not wet the entire surface. The mention of roughening one side of the plate and using both sides suggests a possible explanation for the factor of two in the calculations. Clarification on these points is sought to resolve the confusion surrounding the correct application of the method.
lyhuyen
I found two different resources which give two different but similar formulae to calculate surface tension for Wilhelmy plate method: in one formula, the surface tension (ST) force is devided by the perimetor of the plate; in the other one, ST force is divided by twice the perimetor.

Which one is correct?

And can someone please explain me why it is the perimetor? Since the liquid doesn't wet the whole rectangular plate, shouldn't it be twice the length of the plate? (given that the thinness is negligible).

Thanx in advance.
 
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It would help if you gave some links but I think I see your problem. In one of the links I read, they roughen up one side of the plate and in another, they use both sides. That could account for your unexplained factor of two??
 

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