Polypropylene spheres of 20 mm diameter were fluidized by air in a column of 290 mm diameter. Liquid was added to the bed countercurrent to the gas, such that the turbulent action of the fluidized spheres promoted mass transfer between the gas and liquid. An aqueous solution of calcium chloride was used as the liquid which dehumidified the originally saturated air. Humidities and temperatures of the air were measured at three points : the inlet to the bottom of the column; just below the supporting grid of the fluidized bed; and at the exit from the fluidized bed. The lower column below the grid acted as an air flow straightener and a collection system for the liquid leaving the bed. Volumetric mass transfer coefficients, K(g)a, were measured for the lower column and the fluidized bed over a range of bed heights, liquid flowrates and gas flowrates. Values of K(g)a increased slightly with increasing liquid flowrate. K(g)a was found to decrease slightly with bed height. The value of K(g)a for the fluidized bed increased, passed through a maximum, and then decreased with gas flowrate. K(g)a for the lower column increased with increasing gas flowrate, with a distinct change in the rate of increase taking place at mid-range. A dispersion/coalescence model has been proposed to explain variations in K(g)a with gas velocity.