Gas absorption by large rising bubbles

The absorption rate of carbon dioxide from single rising bubbles of equivalent diameter 0·8–4·2 cm in water has been measured. The results have been compared with a theoretical equation for absorption at the upper surface of a spherical cap bubble.The absorption rates in tap water are about 50 per cent greater than is predicted by this theory because of absorption by the rippling rear surface of the bubble. The ripples can be suppressed by adding n-hexanol to water and the absorption rate is then approximately as predicted. Aqueous solutions of Lissapol absorb the gas up to 50 per cent slower than the theory predicts. This is believed to be due to a stagnant layer which partly covers the front surface of the bubble.Bubbles whose equivalent diameters exceed about 2·5 cm absorb at an unsteady rate, decreasing with time. There is evidence that this is due to the gradual saturation of the liquid being carried up behind the bubble.