When stirring of two immiscible liquids, we speak of dispersing one liquid in the other. In this process, one liquid is broken up into droplets, and the other constitutes the continuous phase. This greatly increases the interface between the phases that is available for the exchange of substances. Dispersion is applied in polymerization and extraction processes.
Together with the list of ingredients, stirring determines the droplet size and hence the size of the interface.
Liquid dispersions are usually unstable and when one stops stirring, the phases quickly separate. One should also be wary of phase inversion, i.e. the sudden change of the continuous and dispersion phase.
Dispersing from gas
By feeding a gas into the mixing vessel under the stirrer, a gas dispersion can be created. Gas dispersions are used in, for example, biotechnology, water purification and to harden fats. The size of the gas bubbles is usually one to several millimetres. A large interface is created in a gas dispersion, which is beneficial for mass transfer.