Determination of water activity in ammonium sulfate and sulfuric acid mixtures using levitated single particles

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  • Yong Pyo Kim
  • Betty K.-L. Pun
  • Chak K. Chan
  • Richard C. Flagan
  • John H. Seinfeld


Original languageEnglish
Pages (from-to)275-284
Journal / PublicationAerosol Science and Technology
Issue number3
Publication statusPublished - 1994
Externally publishedYes


Water activities of ammonium sulfate-sulfuric acid mixtures with ammonium to sulfate molar ratios between 0 and 2 were measured by a spherical void electrodynamic levitator at relative humidities (RH) of 0.18–0.90. Since the composition of the solid particles is subject to uncertainty, solution properties were determined relative to the known properties at RH about 0.75–0.90. The data were compared with other measurements and the estimates from the Zdanovskii-Stokes-Robinson (ZSR) method and SCAPE, a newly developed gas-particle equilibrium model, and generally were found to be in good agreement. © 1994 Elsevier Science Inc.