The critical micelle concentration CMC of sodium dodecyl sulfate SDS in water is approximately 8 mM millimolar at 25C. The CMC is the concentration at which surfactant molecules, like SDS, start to aggregate and form micelles in a solution.The CMC of SDS can vary with temperature and the presence of electrolytes:1. Temperature: As the temperature increases, the CMC of SDS generally decreases. This is because the hydrophobic effect, which drives micelle formation, becomes stronger with increasing temperature. Consequently, micelles form more readily at higher temperatures, and the CMC decreases.2. Presence of electrolytes: The addition of electrolytes to the SDS solution can also affect the CMC. In general, the presence of electrolytes reduces the CMC of SDS. This is because the added ions can shield the repulsive forces between the negatively charged head groups of SDS molecules, promoting micelle formation. The extent to which the CMC is reduced depends on the type and concentration of the electrolyte. For example, the addition of sodium chloride NaCl to an SDS solution will decrease the CMC more significantly than the addition of a weaker electrolyte like sodium sulfate Na2SO4 .In summary, the CMC of SDS in water is approximately 8 mM at 25C, and it generally decreases with increasing temperature and the presence of electrolytes.