The critical micelle concentration CMC of Sodium Dodecyl Sulfate SDS in water at room temperature 25C and pH 7 is approximately 8 mM millimolar or 0.008 mol/L. However, it is important to note that the CMC value can vary slightly depending on the specific experimental conditions and the purity of the SDS used.The CMC of SDS can be affected by changes in temperature and pH:1. Temperature: As the temperature increases, the CMC of SDS generally decreases. This is because the hydrophobic effect, which drives micelle formation, becomes stronger at higher temperatures. The increased thermal motion of water molecules at higher temperatures makes it more difficult for them to maintain an ordered structure around the hydrophobic tails of the surfactant molecules, leading to a lower CMC.2. pH: The CMC of SDS is not significantly affected by pH in the range of 5-9, as the sulfonate headgroup of SDS remains negatively charged within this pH range. However, at extremely low or high pH values, the CMC may be affected due to changes in the ionization state of the headgroup or the counterion sodium ion .The presence of dissolved salts can also affect the CMC of SDS:1. Salts with monovalent cations e.g., NaCl, KCl : The presence of salts with monovalent cations generally leads to a decrease in the CMC of SDS. This is because the added cations can shield the negative charges on the SDS headgroups, reducing the electrostatic repulsion between the surfactant molecules and promoting micelle formation.2. Salts with divalent or multivalent cations e.g., CaCl2, MgCl2 : The presence of salts with divalent or multivalent cations can have a more pronounced effect on the CMC of SDS, leading to a significant decrease in the CMC. This is due to the stronger charge screening effect of these cations, which can more effectively reduce the electrostatic repulsion between the SDS headgroups.In summary, the CMC of SDS in water at room temperature and pH 7 is approximately 8 mM. The CMC decreases with increasing temperature and is not significantly affected by pH within the range of 5-9. The presence of dissolved salts, particularly those with divalent or multivalent cations, can lead to a decrease in the CMC of SDS.