The interfacial surface area concentration in a short vertical column subject to the through flow of a solid-liquid-gas slurry made by mixing aqueous fibrous paper pulp with a nitrogen-carbon dioxide gas mixture was measured in the study. The gas absorption technique was applied, using CO2 as the transferred species and sodium hydroxide as the alkaline agent in water. The flow regimes in the experiments were visually identified, and the test section void fraction was measured using a Gamma-ray densitometer. The test section was a 1.83 m-long column with 5.08 cm inner diameter. The ranges of experimental parameters were as follows: liquid-pulp superficial velocity 15-94 cm/s; average gas-superficial velocity 17-54.5 cm/s; pulp consistency in the water/pulp mixture 0.0-2.18%; and average mole fraction of carbon dioxide in the gas mixture 0.19-0.95. A total of 33 data points were obtained, each representing the average of three to nine tests that confirmed reasonable repeatability. Statistical analysis of the experimental data indicates strong dependence of interfacial area on average gas superficial velocity and void fraction; and a relatively weak dependence on pulp consistency and liquid superficial velocity. The effect of pulp consistency on the interfacial area concentration in the test section was particularly interesting. The test section average interfacial surface area concentration decreased with increasing consistency up to a consistency of 1.6%, but increased significantly when consistency was further increased to 2.18%. The experimental data were empirically correlated. (C) 2004 Elsevier Ltd.