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1708290 
Journal Article 
THE IONIZATION OF SULFUROUS ACID IN NA-MG-CL SOLUTIONS AT 25-DEGREES-C 
Roy, RN; Zhang, JZ; Millero, FJ 
1991 
Yes 
Journal of Solution Chemistry
ISSN: 0095-9782
EISSN: 1572-8927 
20 
4 
361-373 
WOS:A1991FE95600001 
The stoichiometric pK1* and pK2* 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-degrees-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 HSO3- yielded lambda = 0.085 +/- 0.004, beta-(0) = 0.35 +/- 0.02, beta-(1) = 1.22 +/- 0.04, and C-phi = -0.072 +/- 0.007. The Pitzer parameters beta-(0) = -2.8 +/- 0.4, beta-(1) = 12.9 +/- 2.9 and beta-(2) = - 201 +/- 57 have been determined for the interactions of Mg2+ with SO3(2-). The calculated values of pK1* and pK2* using Pitzer's equations reproduce the measured values to within +/- 0.04 pK units. The ion pairing model with log-K(MgSO3) = 2.36 +/- 0.02 and log-gamma-MgSO3 = 0.102I, reproduces the experimental values of pK2* 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 HSO3- and SO3(2-) in seawater, brines and marine aerosols containing Mg2+ ions. 
IONIZATION; SULFUROUS ACID; PITZER EQUATIONS; SOLUBILITY; NAMGCL; SO2; ACTIVITY COEFFICIENT; ION PAIRING