Investigating the Phase Inversion of Pickering Emulsions: An Experiment To Explore Colloid and Interface Chemistry Concepts.

A new experiment based on phase inversion of Pickering emulsions was carried out in a physical chemistry course. The emulsions were stabilized by surfactant-modified SiO[sub 2] particles. As the concentration of surfactant increased, the emulsions changed from oil-in-water type (O/W) to water-in-oil type (W/O) type, and then reverted to be O/W type again. This double phase inversion of emulsions proved to be an ideal indicator for the adsorption of surfactant on particle surfaces. The students gained preliminary lab skills and improved their understanding of the basic concepts in colloid and interface chemistry. In addition, students were encouraged to work out a mechanism to explain the phase inversion; this practice helped strengthen and improve their reasoning abilities. [ABSTRACT FROM AUTHOR]