Surface Tension Method Determine surface tension of solution towards several different concentrations, and then draw a graph of surface tension against log C the logarithm of concentration, and the turning points is the CMC. Technique Various technique available one of which is Will Helmy side method Principle Force is required to detach a thin microscopic slide of known thickness and width from the surface of liquid is measured.
7. Graph log of Concentration Vs Surface tension For assaying CMC by measurement of surface tension is simple and straightforward. A graph of surface tension versus log concentration is produced. The CMC is found as the point at which two lines intersect; the baseline of minimal surface tension and the slope where surface tension shows linear decline.
8. 1. At very low concentrations of surfactant only slight change in surface tension is detected. 2. Additional surfactant decreases surface tension 3.Surface becomes fully loaded, no further change in surface tension.