A radial-flow scrubber in which a gas is passed downwardly through an annular gap after having been treated with a liquid in which the gap is adjusted by a ring disposed below the orifice for the gas/liquid mixture and shiftable toward and away from the latter on one end of a fluid-containing diaphragm, especially a metal bellows. The fluid pressure in the bellows may be maintained at atmospheric levels or may be adjusted by sealing the bellows or feeding fluid under pressure thereto. Advantageously the pressure within the bellows, to control the expansion or contraction thereof is a function of the pressure of the liquid/gas mixture or its flow velocity.
