Abstract: Gas-liquid contacting efficiency is enhanced in a horizontal scrubbing vessel having first and second baffle means forming a series of side-by-side compartments across the vessel and arranged so that gas flows from the upper-most portion of each compartment and is directed downward so as to enter the next downstream compartment at the bottom-most portion thereof for upward flow therein. Scrubbing liquid is sprayed downward into each compartment for countercurrent gas-liquid contact herein. The liquid collected at the bottom of each compartment is passed to the top of the next upstream compartment for full countercurrent flow through and across the vessel, with the scrubbing liquid being reactivated and recycled to the furthermost downstream compartment. When a common liquid collection means is provided for all compartments, the reactivated liquid can be recycled to the spraying means of each compartment in parallel so that the gas contacts freshly reactivated liquid in each compartment.