Microemulsions with excellent water solubilizing capacity at high hydrocarbon levels with quaternary ammonium salts as surfactants

In W/O microemulsions prepared by adding dry surfactant to a mixture of 85% heptane or toluene and 15% pentanol, then titrating with water, systems using quaternary ammonium salts have been shown to be capable of solubilizing much larger amounts of water than systems using the anionic sodium dodecyl sulfate. In homologous series in the range C₁₂ to C₁₆ it would appear that, with one exception, longer chain length quaternary salts are more effective at solubilizing water than are shorter chain length compounds. With quaternary salts of equal chain length, pyridinium salts are more effective at solubilizing water at high surfactant concentrations than are corresponding trimethyl salts.