TABLE OF CONTENTS If we pour a small amount of alcohol into a flask containing water, we find that a single homogeneous liquid exists over a broad compositional range of relative alcohol and water concentrations. These liquids are said to be completely miscible. In contrast, if we pour a small amount of oil into a similar flask containing water or vinegar, we find that a single liquid is not stable and that the mixture will spontaneously separate into two liquids, with the less dense floating on the surface of the more dense. In this case, the liquids are said to be immiscible, and the mixture is said to be phase separated.
If we seal the opening in the flask containing the oil and water and vigorously shake the mixture, we will form small, dispersed droplets of one of the liquids in a matrix of the other liquid. Since oil and water are both very fluid liquids, the more dense liquid will rapidly sink to the bottom of the flask, while the less dense liquid rises to the surface. The original two layered structure will rapidly reappear. If we carefully pour the contents into a beaker, we can recover almost all of the oil, with very little contamination by water.
What change in this behavior would we observe if these liquids were very viscous? In this case, the rate of separation would be severely depressed. If we rapidly decreased the temperature to below the freezing temperature of both liquids,...
