FIG. 10 A bubble at the interface between two immiscible liquids, showing the pa-rameters needed to calculate the free energy of formation of the critical bubble.

In addition to the modifications to Eq. (16), the preexponential, C′′′′′ includes a factor of as it did for the case of the smooth solid surface. Equation (18) is clearly predicated on the assumption of thermodynamic equilibrium when calculating the work of formation of the critical nucleus. This is equally true for other treatments that involve the contact angle as a variable. Given that all nucleation takes place well away from equilibrium, it is

important to keep in mind the possibility of misleading interpretations from this cause. Specifical-ly, this stricture applies to the use of Eq. (18) for liquid drops that are superheated while rising through a second immiscible liquid.