Simple rules of science are sometimes in conflict with experimental results. Wellknown models do not always describe the mechanisms of real systems.
Potassium cetyl phosphate (PCetP) is such a material in which several rules are broken when it is used as emulsifier. HLB estimation methods1 would not predict that this anionic surfactant is an effective emulsifier. Macroemulsions based on it are remarkable in terms of their long-term stability and they show an extraordinary degree of robustness.
PCetP is neither water- nor oil-soluble as it tends to build-up natural membranes at interfaces. A synergism can be achieved when using long chain fatty alcohols as a partner. Valuable gel-like emulsions can be obtained in a natural way due to the formation of lamellar structures. This is similar to what is known about the essential role of phospholipids for living cells.
As shown in Figure 1, common anionic surfactants, like sodium lauryl ether sulfate, sodium