Air Bubbles in Water

Abstract

The solubility of air bubbles is observed in a variety of experiments. Freely rising bubbles exhibit a solution rate more than twice that of bubbles which are stationary: i.e., trapped on the walls of the container. The theory of solution of stationary bubbles is given but the theory of a free bubble is difficult and has not been solved. Stationary bubble observations lead to a determination of the coefficient of diffusivity: 2.9×10−5 cm2/sec at 27°C; the temperature dependence is considerable, obeying Einstein's equation relating diffusion and viscosity. The effect of surface contamination on diffusion is analyzed; bubble solution in the presence of contaminants is not greatly altered. Experiments are described showing that air bubbles of dimension less than 1μ lodged on hydrophobic particles are not soluble and can exist indefinitely. It is shown that hydrophobic particle residues frequently remain after bubble solution, even in relatively pure water. These residues function as bubble nuclei for boiling or for cavitation.