Absorption of carbcn dioxide into aqueous solution of sodium hydroxide was studied in a packed column under conditions such that the accompanying reaction was of the second order. In this case the average or volumetric reaction factor for the packed column, i.e. the ratio of the volumetric coefficients for absorption with and without chemical reaction, is complicated by the non-uniform contact-time distribution. However, the assumption of Porter''s "long, slow flow paths" model for the contact-time distribution led to a successful correlation for the average reaction factor.