For a stable emulsion, the volume of the dispersed phase should not exceed 50% of the total volume.

• A. Cannot be determined
• B. True
• C. Not specified
• D. False

Answer: (B)

Stability of an emulsion is strongly influenced by how much of the total volume is in the dispersed phase. As the dispersed-phase volume fraction rises toward about 0.5, the system nears the phase inversion point, where the continuous and dispersed phases switch roles. That inversion often leads to instability or a change in emulsion type, so for a given emulsion type (for example oil-in-water), keeping the dispersed phase at or below 50% helps preserve the intended structure and prevents inversion. In practice, more dispersed phase means more droplets and interfacial area that must be stabilized by the emulsifier; if the emulsifier isn’t sufficient or the droplets start to coalesce, stability drops. While there are specialized systems (like high internal phase emulsions) that can tolerate higher dispersed-phase fractions with additional stabilization, the general guideline used in formulations is that the dispersed phase should not exceed half of the total volume.