Journal of Solution Chemistry

, Volume 20, Issue 4, pp 361–373 | Cite as

The ionization of sulfurous acid in Na−Mg−Cl solutions at 25°C

  • Rabindra N. Roy
  • Jia-Zhong Zhang
  • Frank J. Millero
Article

Abstract

The stoichiometric pK 1 * and pK 2 * for the ionization of sulfurous acid has been determined from emf measurements in NaCl solutions with varying concentrations of added MgCl2 (m=0.1, 0.2 and 0.3) from I=0.5 to 6.0 molal at 25°C. These experimental results have been treated using both the ion pairing and Pitzer's specific ion-interaction models. The Pitzer parameters for the interaction of Mg2+ with SO2 and HSO 3 yielded λ=0.085±0.004, β(0) = 0.35±0.02, β(1) = 1.2±0.04, and Cφ = −0.072±0.007. The Pitzer parameters β(0) = −2.8±0.4, β(1) = 12.9±2.9 and β(2) = −2071±57 have been determined for the interactions of Mg2+ with SO 3 2− . The calculated values of pK 1 * and pK 2 * using Pitzer's equations reproduce the measured values to within ±0.04 pK units. The ion pairing model with log KMgSO3=2.36±0.02 and logγMgSO3 = 0.1021, reproduces the experimental values of pK 2 * to ±0.01. These results demonstrate that treating the data by considering the formation of MgSO3 yields a better fit of the experimental measurements with fewer adjustable parameters. With these derived coefficients obtained from the Pitzer equations and the ion pairing model, it is possible to make reliable estimates of the activity coefficients of HSO 3 and SO 3 2− in seawater, brines and marine aerosols containing Mg2+ ions.

Key words

Ionization sulfurous acid Pitzer equations solubility NaMgCl SO2 activity coefficient ion pairing 

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Copyright information

© Plenum Publishing Corporation 1991

Authors and Affiliations

  • Rabindra N. Roy
    • 1
  • Jia-Zhong Zhang
    • 2
  • Frank J. Millero
    • 2
  1. 1.Chemistry DepartmentDrury CollegeSpringfield
  2. 2.Rosenstiel School of Marine and Atmospheric ScienceUniversity of MiamiMiami

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