Absorption of NO2/N2O4 in nitric acid

Laboratory‐scale measurements were performed on the absorption of NO2 gas into diluted nitric acid. The concentration of NO2 gas, which represents an NO2/N2O4 equilibrium, varied from 1000 to 20000 ppm, the carrier gas being nitrogen. The concentration of nitric acid ranged from 15 to 60 mass‐%. The absorption experiments were carried out in a double stirred cell, with a defined gas/liquid interface as the mass transfer area. The liquid phase was conducted periodically and the gas phase continuously. Mass flow rates were determined. The well‐known film model of absorption was used for analyzing the experimental results. Only the N2O4 species was considered to pass the gas/liquid interface. The measured data yielded values of H (k D1)1/2 as well as their variation with temperature and nitric acid concentration.