The critical micelle concentration CMC of a surfactant like sodium dodecyl sulfate SDS is the concentration at which micelles start to form in a solution. The CMC is a property of the specific surfactant and depends on factors such as temperature, ionic strength, and the presence of other solutes.For sodium dodecyl sulfate SDS in water at 25C, the CMC is typically reported to be around 8.2 x 10^-3 mol/L or 8.2 mM. This value can vary slightly depending on the specific experimental conditions and the purity of the SDS used.