Abstract
RECENT articles on the formation of atmospheric aerosols from NH3–SO2–H2O gas phase reactions1,2 have considered only those products formed between the anhydrous gases to give 2:1 and 1:1 (NH3: SO2) compounds. I wish to draw attention to my work3 on the reaction between these gases at partial vapour pressures in air of 50 to 500 N m−2. Solid products were formed only in the presence of water vapour at 20° C. Analyses showed that the compounds formed were either ammonium sulphite (with excess NH3) or ammonium pyrosulphite (with excess SO2). Vapour pressure measurements at 0 to 23° C indicated that the extrapolated vapour pressures of NH3 and SO2 above the sulphite in dry air at −70° C would be about 1 × 10−4 and 5 × 10−5 N m−2 respectively. With 50% saturation of the air with water vapour at −70° C, however, these vapour pressures would be depressed to 8 × 10−6 and 4 × 10−6 N m−2 respectively, that is, to concentrations approximately equal to those reported for the 2:1 compound. The partial vapour pressures of the pyrosulphite under similar conditions would be 3.3 × 10−5 N m−2 for both gases. At −52° C the vapour pressures of these gases in dry air would be identical for both the 2:1 compound and ammonium sulphite.
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Black, L. B., Moorbath, S., Pankhurst, R. J., and Windley, B. F., Nature phys. Sci., 244, 53 (1973).
Arrowsmith, A., Hedley, A. B., and Beer, J. M., Nature phys. Sci., 244, 105 (1973).
Scargill, D., J. chem. Soc., A, 2461 (1971).
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SCARGILL, D. Particle Formation from NH3-SO2-H2O-Air Gas Phase Reactions. Nature 247, 101 (1974). https://doi.org/10.1038/247101a0
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DOI: https://doi.org/10.1038/247101a0
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