The pK2* for the dissociation of H2SO3 in NaCl solutions with added Ni2+, Co2+, Mn2+, and Cd2+ at 25°C

Rabindra N. Roy, Jia Zhong Zhang, Marilyn A. Sibblies, Frank J. Millero

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10 Scopus citations


The pK2* for the dissociation of sulfurous acid from I=0.5 to 6.0 molal at 25°C has been determined from emf measurements in NaCl solutions with added concentrations of NiCl2, CoCl2, McCl2 and CdCl2 (m=0.1). 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 M2+ with SO32- yielded {Mathematical expression} The calculated values of pK2* using Pitzer's equations reproduce the measured values to within ±0.01 pK units. The ion pairing model yielded {Mathematical expression} for the formation of the complex MSO3. The stability constants for the formation of MSO3 complexes were found to correlate with the literature values for the formation of MSO4 complexes.

Original languageEnglish (US)
Pages (from-to)467-478
Number of pages12
JournalJournal of Solution Chemistry
Issue number5
StatePublished - May 1 1991


  • Dissociation constant
  • NaCl solution
  • Pitzer parameter
  • ion pairing model
  • potentiometric titration
  • sulfurous acid
  • transition metal

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Physical and Theoretical Chemistry


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