Occurrence of Cloud Points in Sodium Dodecyl Sulfate−Tetra-n-butylammonium Bromide System

Here we report the clouding phenomenon with sodium dodecyl sulfate (SDS) in combination with tetra- n -butylammonium bromide (Bu 4 NBr). Cloud point (CP) vs [Bu 4 NBr] curves are constructed for various fixed [SDS], and the minimum Bu 4 NBr concentrations required to produce CP are determined. A relationship between [SDS] and [Bu 4 NBr] is established that exists down to fairly low [SDS]. The presence of aromatic hydrocarbons (added up to their solubility limits) decreases the CP of a fixed SDS−Bu 4 NBr system. Furthermore, an increase in hydrophobicity of the aromatic hydrocarbon decreases the CP. An unusual CP-decreasing effect of thio compounds is observed, which is discussed in terms of direct interaction of these compounds with anionic SDS micelles.