Measurement of surface tension based on weighing or force method is very popular on account of development of Wilhelmy Plate method or DuNouy Ring method. Visit http://www.uskino.com/article/72.html to find more information about Wilhelmy plate method and DuNouy Ring method.
Benefitted by Modified Wilhelmy Plate method (3th generation Wilhelmy Plate method based on Young-Laplace equation correcting method), surface tensiometer with model A601 or model A801 can achieve such measurement of surface tension as measurement of viscous sample and surfactant (surface tension will be changed via time), because in modified Wilhelmy plate method, plate needs not such process as immersing and withdrawing plate from liquid sample. So, when we use modified Wilhelmy plate method to measure surface tension of surfactant via time and critical micelle concentration (CMC), it will be easier and more quickly.
Diagram of different Wilhelmy plate method for measurement of surface tension using surface tensiometer
1, Modified Wilhelmy plate method
2, Classical Wilhelmy plate method (Max pull)
3, Classical Wilhelmy plate method (Zero buoyance method)
Note：This method is used in surface tensiometer made by Kruss, KSV, KYOWA. And it cannot used to measure surface tension of cationic surface active agent and sample with viscosity due to its immersing and drawing out process.
So, we can measure critical micelle concentration (CMC) by manual instead of automatic way to save costs, and we find out that by manual way, it is easy to find critical point. You can refer video below to learn how to measure critical micelle concentration (CMC) of surfactant by method of measuring surface tension. And we find out that measure critical micelle concentration (CMC) automatically that used in meter made by other manufactory that without modified Wilhelmy plate method may waste time and energy with poor resolution. Because, when plate immersed and withdrew from sample, Langmuir film layer will be more inclined to be formed during this process and stable surface tension is more difficult to decide even if we have stirred sample before measuring surface tension at each step. So, if you are careful enough, you can find out measuring process with modified Wilhelmy plate method is different from classical Wilhelmy plate method (zero buoyance method) far away.
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