The recently proposed mathematical model of Suchak et al., A.I. Ch. E. Jl. 37, 23 (1991) for the absorption of NO, into nitric acid solutions in a countercurrent how packed column has been modified by taking into account separate energy balances for the gas and liquid phases and variation of the molar flow rates of water and nitric acid in the liquid phase as a function of the height of the column.