The solubility of SO₂ and the dissociation of H₂SO₃ in NaCl solutions

The pK₁^* and pK₂^* of H₂SO₃ have been determined in NaCl solutions as a function of ionic strength (0.1 to 6 m) and temperature (5 and 25 °C). The extrapolated values in water were found to be in good agreement with literature data. The experimental results have been used to determine the Pitzer interaction parameters for SO₂, HSO₃^-and SO₃^-in NaCl solutions. The resultant parameters for NaHSO₃ and Na₂SO₃ were found to be in reasonable agreement with the values for NaHSO₄ and Na₂SO₄. It, thus, seems reasonable to assume that the interactions of Mg²⁺ and Ca²⁺ with HSO₃^-and SO₃^-can be estimated from the values with HSO₄^-and SO₄^-until experimental values are available. Measurements of pK₁^* and pK₂^* in artificial seawater were found to be in good agreement with the calculated values using the derived Pitzer parameters. It is, thus, possible to make reasonable estimates of the activity coefficients of HSO₃^-and SO₃^-ions and pK₁^* and pK₂^* for the ionization of H₂SO₃ in marine aerosols.