Bubble formation in supersaturated gelatin: A further investigation of gas cavitation nuclei

Recently, a new cavitation model has been proposed in which bubble formation in aqueous media is initiated by spherical gas nuclei stabilized by surface‐active membranes of varying gas permeability. The data which originally motivated this development were obtained mainly by subjecting shallow gelatin samples to rectangular pressure schedules consisting of a rapid compression, equilibration of the sample at some constant increased pressure, and a rapid decompression. Since the initial pressure was ordinarily less than or equal to the final pressure, the magnitude of the initial compression was ordinarily greater than or equal to the magnitude of the final decompression. An equivalent statement for this type of schedule is that the initial overpressure was generally greater than or equal to the final supersaturation. The purpose of the experiment reported here is to test the surfactant cavitation model in the unexplored domain for which the reverse is true, i.e., for which the maximum overpressure is less than the final supersaturation. This domain can be reached by using slow compressions or stepped compressions which permit a significant rise in the dissolved gas tension while the ambient pressure is still increasing.