CHEMICAL OSCILLATIONS AND INSTABILITIES .100. UNSTABLE SUPERSATURATEDSOLUTIONS OF GASES IN LIQUIDS AND NUCLEATION THEORY

Limiting supersaturations for dissolved gases manifested by gas evolut ion oscillators and by direct experiments cannot be accounted for by t he application of classical nucleation theory (CNT). The theory predic ts bubbles containing 10(4)-10(5) molecules at nucleation, with Helmho ltz energies of ca. 10(4)kT per bubble, much too high for homogeneous nucleation to occur spontaneously in a finite time. We investigate alt ernative unstable structures ('blobs') which do not have well-defined interfaces, which may exist transiently at the point of nucleation as the precursors of true bubbles and which circumvent the need for a lar ge Helmholtz energy for their formation. Effects due to global or loca l depletion of the solution concentration at nucleation are also consi dered.