Ouzo effect

If then the concentration of ethanol is lowered by addition of more water the hydrophobic substance precipitates from the solution and forms an emulsion with the remaining ethanol-water-mixture.

Addition of a small amount of surfactant or the application of high shear rates (strong stirring) can stabilize the oil droplets.

Based on thermodynamic considerations of the multi-component mixture, the emulsion derives its stability from trapping between the binodal and spinodal curves in the phase diagram.

[3] However, the microscopic mechanisms responsible for the observed slowing of Ostwald ripening rates at increasing ethanol concentrations appear not fully understood.

The ouzo effect is seen as a potential mechanism for generating surfactant-free emulsions without the need for high-shear stabilisation techniques that are costly in large-scale production processes.