Phase Behavior of Alcohol-Free Microemulsion Systems Containing Butyric Acid as a Cosurfactant

The phase behavior of the alcohol-free microemulsion systems comprising of sodium dodecyl sulfate (SDS) + butyric acid + alkane + NaCl solution has been studied with an ε−β fishlike phase diagram method. The composition of the hydrophile−lipophile balanced (HLB) interfacial layer, the solubility of butyric acid, and the solubilization ability of the system, and so forth, were determined. The effects of the composition of the water phase, such as salts, acids, and alkali, and temperature on the phase behavior were investigated. As the salinity increases, the solubilization ability increases. The cations of the salts have notable influence on the phase diagrams. The influence of acid (HCl) is similar to that of salt (NaCl). However, alkali (NaOH) can remarkably affect the phase diagrams and shift the fish body to an upper position. A comparison of the ε−β phase diagrams is also made between the butyric acid-containing microemulsion systems and the 1-butanol-containing microemulsion systems.