Abstract: In an apparatus for contacting a gas with a liquid, the gas is caused to flow upward through a vertical channel associated with a device for charging the channel with a foam containing the liquid. The channel contains upper and lower gas-permeable elements each arranged to support a layer of the foam covering the through-flow area of the channel, each element being formed to cause turbulence of the gas flowing therethrough. The two foam-supporting elements are located so close to each other that foam is entrained by the flowing gas from the space between the elements upwardly through the upper element to the upper side thereof, from which foam is returned through a passage to the space between the two elements. This return passage is shielded from upward flow of gas therethrough, so that a foam column in the passage can move downward.