The critical micelle concentration CMC of a surfactant, such as sodium dodecyl sulfate SDS , is the concentration at which the surfactant molecules start to aggregate and form micelles in a solution. The CMC is an important parameter in understanding the behavior of surfactants in various applications, such as detergents, emulsifiers, and stabilizers.For sodium dodecyl sulfate SDS in water at 25C, the CMC is typically reported to be around 8-10 mM millimolar . This value can vary slightly depending on the purity of the SDS and the experimental conditions used to determine the CMC.To determine the CMC experimentally, several methods can be employed, including surface tension measurements, conductivity measurements, and fluorescence spectroscopy. Here, I will describe the surface tension method as an example.In the surface tension method, the surface tension of a series of SDS solutions with varying concentrations is measured at 25C. As the concentration of SDS increases, the surface tension of the solution decreases due to the adsorption of SDS molecules at the air-water interface. When the concentration reaches the CMC, the surface tension reaches a plateau, as the SDS molecules start to form micelles in the bulk solution rather than adsorbing at the interface.A plot of surface tension versus the logarithm of SDS concentration will show a clear breakpoint at the CMC. The surface tension will decrease rapidly with increasing SDS concentration at low concentrations, and then level off at higher concentrations. The concentration at which this breakpoint occurs is the CMC.In summary, the critical micelle concentration CMC of sodium dodecyl sulfate SDS in water at 25C is around 8-10 mM. This value can be determined experimentally using methods such as surface tension measurements, conductivity measurements, or fluorescence spectroscopy. The CMC is an important parameter for understanding the behavior of surfactants in various applications.