Determination of phase transfer parameters for the uptake of HNO3, N2O5 and O3 on single aqueous drops

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A new method for the investigation of phase transfer on gas–liquid interfaces is introduced. It allows the in situ analysis of single drops that are produced inside a flow tube gas phase reactor. Using this technique, the uptakes of HNO3 and N2O5 on pure water as well as the uptake of O3 on NaI solutions were examined. For HNO3, uptake coefficients γ in the range from 3.1 × 10−3 to 11.8 × 10−3 were measured dependent on the total pressure at 298 K. For N2O5, γ = 3.7–9.1 × 10−3 at 293 K was obtained. For iodide concentrations ranging from 2 × 10−2 M to 4 M, the uptake coefficient of O3 was in the range of 2.0 × 10−4 to 1.5 × 10−2. After correction for the effect of the gas phase diffusion by means of a computer model, the mass accommodation coefficients α were derived from these γ-values, resulting in αHNO3 > 3 × 10−2, αN2O5 = (1.1−0.6 + 1.2) × 10−2, and αO3 > 2 × 10−2. Additionally, the ratio of the rate constants for the reactions of NO2+ with iodide and water, respectively, was determined to be 40 ± 12.