Tubular Flow Reactors With First-Order Kinetics

The Reaction of CIONO2 with Submicrometer Sulfuric Acid Aerosol

The measured reaction probability, gamma for the reaction of chlorine nitrate (CIONa(2)) with 60 percent (by weight) sulfuric acid aerosol increases monotonically with particle size at 250 kelvin. The reacto-diffusive length (l, the effective liquid depth over which reaction occurs) derived from these experiments is 0.037 +/- 0.007 micrometer (95 percent confidence level for precision). The reaction probability for the reaction of CIONO(2) with 60 percent sulfuric acid aerosol doped with approximately 7 x 10(-4) M hydrochloric acid at 250 kelvin is larger by about a factor of 4 than in the absence of hydrochloric acid and varies less with particle size (l = 0.009 +/- 0.005 micrometer). These results provide a test of the theory for gas-particle reactions and further insight into the reactivity of atmospheric aerosol.

Antarctic Stratospheric Chemistry of Chlorine Nitrate, Hydrogen Chloride, and Ice: Release of Active Chlorine

The reaction rate between atmospheric hydrogen chloride (HCl) and chlorine nitrate (ClONO(2)) is greatly enhanced in the presence of ice particles; HCl dissolves readily into ice, and the collisional reaction probability for ClONO(2) on the surface of ice with HCl in the mole fraction range from approximately 0.003 to 0.010 is in the range from approximately 0.05 to 0.1 for temperatures near 200 K. Chlorine (Cl(2)) is released into the gas phase on a time scale of at most a few milliseconds, whereas nitric acid (HNO(3)), the other product, remains in the condensed phase. This reaction could play an important role in explaining the observed depletion of ozone over Antarctica; it releases photolytically active chlorine from its most abundant reservoir species, and it promotes the formation of HNO(3) and thus removes nitrogen dioxide (NO(2)) from the gas phase. Hence it establishes the necessary conditions for the efficient catalytic destruction of ozone by halogenated free radicals. In the absence of HCl, ClONO(2) also reacts irreversibly with ice with a collision efficiency of approximately 0.02 at 200 K; the product hypochlorous acid (HOCI) is released to the gas phase on a time scale of minutes.