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Binary nucleation in acid–water systems. II. Sulfuric acid–water and a comparison with methanesulfonic acid–water

Wyslouzil, B. E. and Seinfeld, J. H. and Flagan, R. C. and Okuyama, K. (1991) Binary nucleation in acid–water systems. II. Sulfuric acid–water and a comparison with methanesulfonic acid–water. Journal of Chemical Physics, 94 (10). pp. 6842-6850. ISSN 0021-9606.

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This work presents a systematic investigation of binary nucleation rates for sulfuric acid and water and the effect of temperature on these rates at isothermal, subsaturated conditions. The results from nucleation rate measurements for the sulfuric acid (H2SO4)–water system are discussed and compared to those previously presented for methanesulfonic acid (MSA)–water [B. E. Wyslouzil, J. H. Seinfeld, R. C. Flagan, and K. Okuyama, J. Chem. Phys. (submitted)]. Experiments were conducted at relative humidities (Rh) ranging from 0.006<Rh<0.65, relative acidities (Ra) in the range of 0.04<Ra<0.46, and at three temperatures, T=20, 25, and 30 °C, in the continuous flow mixing-type apparatus described in Paper I. Particles were formed by binary nucleation and grew by condensation as the mixed stream flowed through an isothermal glass tube. Number concentrations observed at the exit of the nucleation and growth tube as a function of Rh and Ra are extremely sensitive to the binary nucleation rate, and from these data the nucleation rate was estimated as a function of saturation level and temperature. Particle size distributions were also measured using a specially constructed differential mobility analyzer. As anticipated, the H2SO4 particles formed by nucleation and growth are much smaller than those formed in the MSA–water experiments, but particle size distribution measurements confirm that most of the particles formed are being observed. The ratio of experimental to theoretical nucleation rates, Jexpt/Jtheor, was found to be a strong function of the predicted number of acid molecules in the critical nucleus for both the H2SO4–water and MSA–water systems.

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Additional Information:Copyright © 1991 American Institute of Physics (Received 22 October 1990; accepted 29 January 1991) The authors gratefully acknowledge the assistance of Sonia Kreidenweis who provided computer programs used to correlate the physical property data and simulate the experiments. This work was supported by National Science Foundation Grant No. ATM-9003186 and by the Alberta Heritage Scholarship Trust Fund (B.E.W.).
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Deposited On:19 Oct 2006
Last Modified:26 Dec 2012 09:13

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