Difference between two methods of Wilhelmy Plate method for measurement of surface tension

In this video, we show you the difference between two different method of Wilhelmy plate method ( Young-Laplace equation fitting method and zero buoyancy method). We tried to measure surface tension of water while plate wasn't cleaned at all. So surface tension cannot reach to 72.8mN/m as usual. When we measured surface tension of this system using Young-Laplace equation fitting method, the result was about 46mN/m. But if we used zero buoyancy method, the result was  about 68mN/m. The reason is when we measured surface tension of water based on zero buoyancy method, water wets the plate and some water is stayed at the surface of plate. And if we used Young-Laplace equation method, we can find out the system is not clean very quickly by checking over the result of measured water. And min.  volume of liquid by this method can be only about 1mL, because there is not process of immersing and pulling back plate. Visit http://www.uskino.com to find more information about our force tensiometer and optical contact angle meter.