Enthalpy of dilution of [SO2 + salt + H2O] in [salt + H2O] {salt = (NH4)2SO4 or Na2SO4}: Experimental results and modeling

New experimental results are presented for the enthalpy change upon diluting aqueous solutions of sulfur dioxide containing a salt (either ammonium sulfate or sodium sulfate) in aqueous solutions of that salt at about 313 and 352 K. A previously developed thermodynamic model for the vapor–liquid equilibrium of the chemical reacting systems {SO2 + (NH4)2SO4 + H2O} and (SO2 + Na2SO4 + H2O) is extended allowing for the formation of pyrosulfite and for the description of the new experimental results for the enthalpy change upon dilution.