7.6 Phase Volume Ratio

As the volume of the dispersed phase in a macroemulsion increases，the interfacial film expands further and further to surround the droplets of dispersed material，and the basic instability of the system increases. As the volume of the dispersed phase increase beyond that of the continuous phase，the type of emulsion （O/W） or （W/O） becomes basically more and more unstable relative to the other type of emulsion，since the area of the interface that is now enclosing the dispersed phase is larger than that which would be needed to enclose the continuous phase. It often happens，therefore，that the emulsion inverts as more and more of the dispersed phase is added，unless the emulsifying agent is so unbalanced as to be capable of forming only one type of emulsion.