Abstract: Volumtric liquid-phase mass-transfer coefficients of oxygen-water and oxygen-C7 F15COONa aqueous solution systems were determined in a horizontal vessel equipped with a stirrar. Experiments were conducted through the steady physical absorption of oxygen in aqueons solutions. The effects ofvarious parameters, such as L/Dt, Di/Dt, Liquid hold-up, types and number of impellers etc, on the gas-liquid mass transfer coefficient kLa are being discussed. Correlations with experimental results were also given. In addition, a criterion for kLa to be used in the sealing-up of a horizontal vessel of similar geometry was given as: Fr=const. or Pv = const.