Absorption experiments of NO and N02 diluted with nitrogen (NO* concentrations over a few hundred ppm) in aqueous solutions of sodium sulfite and/or bisulfite were performed at 25 °C using the agitated vessels with gas dispersion and with a plane interface. The experimental results were discussed based on the film theory of gas absorption accompanied by fast, pseudo mth order chemical reaction. The reaction between NO and S032was found to be second order with respect to NO and zero order with respect to S032-, and the rate of absorption of NO into the sulfite solution increased as the concentration of N02 in the gas phase increased. As for the absorption of N02 in the sulfite solution, it was found that the absorption rates went through a maximum as the sulfite concentration varied, and the reaction mechanism to absorption was with competitive reactions involving the hydrolysis of N02 and the reaction between N02 and S032-in the liquid film. The reduction of N02 was found to be first order with respect to S032-and first order with respect to N02, and so the value of the second-order rate constant was evaluated, while for the hydrolysis of N02 the reaction order was second order with respect to N02. Also the absorption of N02 into the bisulfite solution was accompanied by competitive reactions as well as in the sulfite solution. In addition, aqueous solutions with various reducing or oxidizing agents were examined for the absorption of N02. Furthermore, the effect of temperature on the absorption of N02 in the sulfite solution was studied at 10, 15, and 25 °C.

A study was made of the absorption of nitrogen dioxide with air as a diluent into aqueous solution of sodium sulfite at 25 °C and atmospheric pressure. An agitated vessel with a plane interface was used to make sure of the effect of additive as an antioxidant of sulfite. For the sulfite solution with no additive a significant difference in the rate of N02 absorption was found between the nitrogen and air diluents. Examining some organic compounds as the additive, it was found that hydroquinone and monoethanolamine have a considerable effect on the inhibition in the sulfite oxidation. Furthermore, in order to discuss the applicability of the kinetics of the reaction between N02 and SO32-, which was proposed in a previous paper, the absorption of N02 diluted with air was carried out in both a bubble cap-and a sieve-tray column. The overall capacity coefficients calculated from the equation based on the dual film theory and gas absorption accompanied by a pseudo mth order reaction were in reasonable agreement with the observations for the bubble cap tray.