The critical micelle concentration CMC of sodium dodecyl sulfate SDS in water varies with temperature and pH. SDS is an anionic surfactant, and its CMC is influenced by factors such as temperature, ionic strength, and pH of the solution.At room temperature 25C , the CMC of SDS in water is approximately 8.2 mM millimolar . As the temperature increases, the CMC generally decreases. For example, at 40C, the CMC of SDS is around 6.5 mM, and at 60C, it is about 4.6 mM.Regarding the pH of the solution, the CMC of SDS is not significantly affected by pH changes in the range of pH 5 to 9. However, at extremely acidic or alkaline conditions, the CMC may be affected due to the ionization state of the surfactant. In highly acidic conditions pH < 2 , the CMC of SDS can increase because the sulfate headgroup of SDS can become protonated, reducing its solubility in water. In highly alkaline conditions pH > 12 , the CMC may also be affected due to the presence of counterions that can interact with the surfactant.It is important to note that the CMC values mentioned above are approximate and can vary depending on the specific experimental conditions and the purity of the SDS used.