The process of black-liquor oxidation is treated theoretically and an equation is derived for design purposes. Capacity coefficients were determined experimentally for two different arrangements of asbestos-cement packing sheets. Data include those obtained from a study of a full-scale commercial oxidation unit as well as those from an investigation using a pilot-scale experimental tower with a modified arrangement of asbestos-cement packing. Results from the pilot-scale study indicate that the modified packing yields higher capacity coefficients than the packing in the full-scale unit although the mass-transfer coefficients are very similar for both packings using the pilot-scale tower under rigorously controlled flow conditions, it was found that the capacity coefficients increase with increase in liquor flow rate and are virtually unaffected by changes in air-flow rate when this is sufficiently high to provide adequate oxygen for the reaction. The significance of the experimental results is discussed in detail.