1. Emulsions

An emulsion is defined as a heterogeneous system in which one liquid is dispersed, in the form of small droplets, in another immiscible liquid. In general, one of the liquids is water, or an aqueous solution, and the other is a water-insoluble organic phase, called oil. Two types of emulsion are therefore possible: water dispersed in oil (inverse W/O emulsion) and oil dispersed in water (direct O/W emulsion). The phase in the form of droplets is called the dispersed phase or inner phase; the dispersing phase surrounding the droplets is called the continuous phase or outer phase.