Problems with the crevice model for bubble nuclei

1 Problems with the crevice model for bubble nuclei 

However, in addition to many problems in describing bubble nucleation in aqueous gels with the crevice model (see below, and Section 3.2), several fundamental observations suggest that this mechanism is not applicable to aqueous media in general (ref. 114). 

Sirotyuk (ref. 25) found that the complete removal of solid particles from a sample of water increased the tensile strength by at most 30 percent, indicating that most of the gas nuclei present in high purity water are not associated with solid particles. Bernd (ref. 15,16) observed that gas phases stabilized in crevices are not usually truly stable, but instead tend to dissolve slowly. This instability is due to imperfections in the geometry of the liquid/gas interface, which is almost never exactly flat (ref. 114). Medwin (ref. 31,32) attributed the excess ultrasonic attenuation and backscatter measured in his ocean experiments to free microbubbles rather than to particulate bodies this distinction was based on the fact that marine microbubbles in resonance, but prior to ultrasonic cavitation (ref. 4), have acoustical scattering and absorption cross sections that are several orders of magnitude greater than those of particulate bodies (see Section 1.1.2). 

In summary, nuclear models of the crevice type consist essentially of gas phases stabilized in crevices in solid particles. While the crevice hypothesis represents a viable nuclear model, none of the existing mathematical treatments make predictions that are supported by the above-mentioned gelatin experiments (ref. 114). In addition to these problems with the mathematical devel- 

2 Reduction of gaseous diffusion across the air/water interface bv selected surfactant monolayers 

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