Bubble nucleation from supersaturated gas solutions generally takes place at much lower supersaturations
than are expected from the theory. Furthermore, the same theory predicts that the threshold concentration
of gas needed to cause nucleation should be essentially independent of the gas species used, a finding
contradicted by experiment. There are two general explanations: first, that the theory is wrong, or second,
that there is a previously unidentified factor which is influencing the results of the experiments. Given
the success of the fundamental theory in other areas, the second explanation is preferred. The previously
unrecognized factor is identified here as being the surface activity of the gases which form the bubbles.
We have investigated the kinetics of swelling of squalane-in-water emulsion drops by the addition of
decane-in-water emulsion drops. Squalane is sufficiently insoluble in the aqueous continuous phase that
it cannot transfer between oil drops. Decane is able to transfer between drops and swells the squalane
drops. The mixed emulsions were stabilized by the nonionic surfactant n-dodecyl octaoxyethylene glycol
ether (C12E8) and were stable with respect to drop coalescence. We have made a systematic series of
experiments in which the swelling rates were determined as functions of the initial drop radii, volume
fractions, and oil compositions of both types of emulsions. Using a theoretical model originally developed
by Ugelstad et al., the entire data set was successfully fitted with a single adjustable parameter equal to
the product of the solubility of decane (C
∞) and its diffusion coefficient in the aqueous continuous phase
(D). The measured value of C
∞
D was consistent with a mechanism of decane transport in which micelles
of C12E8 act as carriers facilitating decane transport between emulsion drops. Also in agreement with this
mechanism, it was observed that increasing the aqueous phase concentration of C12E8 increased the swelling
rate. Ostwald ripening rates of the decane-in-water emulsions gave values of C
∞
D consistent with those
derived from swelling experiments.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.