Viscosity change after dilution with solutions of water--oil--water emulsions and solute permeability through the oil layer.

A water-in-oil-water (W/O/W) multiple phase emulsion was prepared by a two-step emulsification procedure. The oil phase consisted of paraffin oil and sorbitan monooleate. The inner aqueous phase and the outer aqueous phase were 0.5% glucose solution and 3% polysorbate 80 solution, respectively. Viscosity measurements were carried out on the W/O/W emulsion after diluting it with a number of solutions. A given sequence for the solutes that would increase the emulsion viscosity after dilution was determined. This sequence was identical with that obtained with the solutes in an independent permeability experiment using a planar membrane composed of sorbitan monooleate alone. As a result, it was suggested that solutes as well as water can permeate the oil layer of vesicles of the emulsion to change the vesicle volume, thereby causing a change in the emulsion viscosity.