A study of the fluid mechanics of the co-current flow of gas and liquid mixtures through beds of 1 mm. spheres had revealed two regimes of flow inside the pores which were interpreted on the basis of two flow configurations; one in which the pores are predominantly in single-phase flow and the other in which they are predominantly in two-phase flow. These regimes have now been identified on beds with other packings and the interpretation checked by means of gas absorption measurements into liquids with and without a chemical reaction from which interfacial areas were obtained. The holdup was measured by means of a radiation absorption technique. This technique had also been used in the determination of interfacial areas in the process of physical absorption. The interfacial area in the single-phase pore-flow regime is independent of gas flow rate whilst in the two phase pore-flow regime is larger and increases with gas flow rate. Correlations based on dimensional analysis for pressure drop, liquid holdup and interfacial area for each of the two regimes are given.