[en] The absorption of gaseous NO/sub x/ compounds into water and dilute HNO₃ was studied in a three-stage sieve-plate column with plates designed for high gas-liquid interfacial area. The performance of the column was measured while several operating parameters were varied. The results of the study indicate the importance of three mechanisms in the absorption of gaseous NO/sub x/ (NO₂ + 2N₂O4 + NO) compounds: (1) the absorption of NO₂/sup */ (NO₂ + 2N₂O4) which results in production of liquid HNO₃ and HNO₂; (2) the dissociation of the liquid HNO₂ into HNO₃ and gaseous NO; and (3) the gas-phase oxidation of NO to NO₂. A mathematical model based on these mechanisms was developed and is presented to explain the observed phenomena