The critical micelle concentration CMC of sodium dodecyl sulfate SDS in water at room temperature around 25C is approximately 8 mM millimolar or 0.008 mol/L. The CMC is the concentration at which surfactant molecules, such as SDS, start to aggregate and form micelles in a solution.The CMC of SDS can be affected by the presence of salts in the solution. Generally, the addition of salts can decrease the CMC of SDS. This phenomenon is known as the "salting-out" effect. The presence of salts can shield the electrostatic repulsion between the negatively charged head groups of SDS molecules, making it easier for them to aggregate and form micelles.The extent to which the CMC of SDS is affected by salt concentration depends on the type and concentration of the salt. For example, the addition of sodium chloride NaCl to the SDS solution can significantly decrease the CMC. As the concentration of NaCl increases, the CMC of SDS decreases, but the relationship is not linear. The effect of other salts on the CMC of SDS may vary depending on the specific salt and its concentration.