Gas nucleation in the vicinity of solid hydrophobic spheres

The theory of homogeneous nucleation predicts much larger tensile strengths for water than are actually observed. Plesset has suggested that this may result from the presence of solid impurities, and he has carried out specific calculations for hydrophobic spheres. We show that his result implies a low probability for cavitation if (i) the spheres have radii larger than 10 Å and (ii) the thicknesses of the vapor shells surrounding them are required to be at least one average intermolecular distance, about 3 Å in water. Since homogeneous nucleation is expected to be effective in producing vapor phases with radii up to about 10 Å, the presence of smooth spheres of any size, whether hydrophobic or not, can reduce the predicted tensile strength by at most 30%. This is far below the factor of 5 needed to reconcile the theory with experiments.