Nine heavy lubricating oils, four light lubricating oils, three aircraft engine fuels, one diesel fuel, and distilled water were tested for their air solubility and for the rate of solution and evolution of air when equilibrium is disturbed. The technique consisted of shaking of a container partly filled with liquid and taking accurate pressure measurements of the air above the liquid. Since air in solution exerts no pressure, the variation of pressure during and after the agitation furnished information on the amount of air that went into or came out of solution and their time rates. The solution was considered to have reached equilibrium when further shaking no longer changed the air content of the liquid.A wide variation exists in the solubility constants and rates, but the rate of evolution was always found to be proportional to the supersaturation, and the rate of solution to the undersaturation, under otherwise similar conditions. At room temperature the air solubility constant for distilled water is 1.84 percent, for a gasoline approximately 20 percent, and for (light and heavy) lubricating oils approximately 10 percent. The ``half‐life'' for evolution on the other hand was 3.86 sec. for distilled water, 0.13–0.24 sec. for gasoline, 3.6–7.6 sec. for light, and 11.6–51.4 sec. for heavy lubricating oils.The investigation gave some insight into the phenomenon of cavitation which is still largely shrouded in mystery.