The Ouzo Effect: adding a splash of dynamics to the oil/water/ethanol phase diagram

Ouzo is a colorless aniseed-flavor liquor which turns cloudy when diluted with water. This process, known as spontaneous emulsification, occurs as the added water dilutes the ethanol, leading to precipitation of oil-rich microdroplets. Despite much work on the dynamics of this process, the full equilibrium phase diagram for water-ethanol-anise oil has not previously been determined experimentally. We present data determining the two-phase region and the spinodal curve separating unstable from metastable behavior. We also measure the composition of coexisting phases, indicated on the phase diagram by tie lines, identify the plait point (critical point) and determine densities and surface tensions of coexisting phases. We then use this equilibrium data to better understand spontaneous emulsification and other complex dissolution dynamics.