Diffusional Mass Transfer at the Surface of Small Gas Bubbles

A method apt to observe small levitated bubbles in the sub-mm range in liquid is described. The method combines a rotary chamber with a Mie scattering method. The key result of the measurements with this method is the rate at which gas diffuses from the bubble into the liquid. A remarkable result is found for five different gases in water. It turns out that the mass flux density is independent of the radius. This suggests that convective mass transport is not the controlling mechanism.