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A mole-fraction-based thermodynamic model is used to represent available activity data, salt solubilities, and electrodynamic balance measurements for aqueous NaCl, Na2SO4, NaNO3 and their mixtures at 298.15 K. The results are presented as fitted ion-interaction parameters and equilibrium constants. These enable ion and solvent activities, and saturation with respect to five possible solid phases (NaCl, NaNO3, Na2SO4 . 10H(2)O, Na2SO4, and NaNO3 . Na2SO4 . H2O) to be calculated for all mixture compositions to relative humidities of less than or equal to 60\%, and to high degrees of supersaturation with respect to the dissolved salts. Extension of the model to other systems is discussed. (C) 1997 American Association for Aerosol Research.

Water activity/concentration relationships of aqueous NaCl, NaNO3, Na2SO4 and their mixtures from dilute concentration to high supersaturation have been determined at room temperature in an electrodynamic balance. Using a dynamic measurement technique based on the evaporation of the droplets, a set of water activity measurements of a solution droplet can be obtained in less than an hour. The water activities of the mixtures are compared with theoretical predictions of the Pitzer-Simonson-Clegg (PSC) model, the Zdanovskii-Stokes-Robinson (ZSR) equation, and the Kusik and Meissner (KM) model. Comparisons of the data with model predictions indicate that the PSC, ZSR, and KM approaches agree well among themselves and with the experimental data. All three models give similar maximum (+/-0.02) and standard (0.01) deviations in mass fraction of the solute (mfs). These deviations are close to the experimental error of +/-(0.01-0.02). The agreement of the models and the need for single-component water activities at different temperatures, as input for all models, suggest that a high priority should be given to such experiments in the future. (C) 1997 American Association for Aerosol Research.

A mole-fraction-based thermodynamic model is used to represent available activity data, salt solubilities, and electrodynamic balance measurements for aqueous NaCl, Na2SO4, NaNO3 and their mixtures at 298.15 K. The results are presented as fitted ion-interaction parameters and equilibrium constants. These enable ion and solvent activities, and saturation with respect to five possible solid phases (NaCl, NaNO3, Na2SO4 . 10H(2)O, Na2SO4, and NaNO3 . Na2SO4 . H2O) to be calculated for all mixture compositions to relative humidities of less than or equal to 60\%, and to high degrees of supersaturation with respect to the dissolved salts. Extension of the model to other systems is discussed. (C) 1997 American Association for Aerosol Research.

Water activity/concentration relationships of aqueous NaCl, NaNO3, Na2SO4 and their mixtures from dilute concentration to high supersaturation have been determined at room temperature in an electrodynamic balance. Using a dynamic measurement technique based on the evaporation of the droplets, a set of water activity measurements of a solution droplet can be obtained in less than an hour. The water activities of the mixtures are compared with theoretical predictions of the Pitzer-Simonson-Clegg (PSC) model, the Zdanovskii-Stokes-Robinson (ZSR) equation, and the Kusik and Meissner (KM) model. Comparisons of the data with model predictions indicate that the PSC, ZSR, and KM approaches agree well among themselves and with the experimental data. All three models give similar maximum (+/-0.02) and standard (0.01) deviations in mass fraction of the solute (mfs). These deviations are close to the experimental error of +/-(0.01-0.02). The agreement of the models and the need for single-component water activities at different temperatures, as input for all models, suggest that a high priority should be given to such experiments in the future. (C) 1997 American Association for Aerosol Research.

Water activity/concentration relationships of aqueous NaCl, NaNO3, Na2SO4 and their mixtures from dilute concentration to high supersaturation have been determined at room temperature in an electrodynamic balance. Using a dynamic measurement technique based on the evaporation of the droplets, a set of water activity measurements of a solution droplet can be obtained in less than an hour. The water activities of the mixtures are compared with theoretical predictions of the Pitzer-Simonson-Clegg (PSC) model, the Zdanovskii-Stokes-Robinson (ZSR) equation, and the Kusik and Meissner (KM) model. Comparisons of the data with model predictions indicate that the PSC, ZSR, and KM approaches agree well among themselves and with the experimental data. All three models give similar maximum (+/-0.02) and standard (0.01) deviations in mass fraction of the solute (mfs). These deviations are close to the experimental error of +/-(0.01-0.02). The agreement of the models and the need for single-component water activities at different temperatures, as input for all models, suggest that a high priority should be given to such experiments in the future. (C) 1997 American Association for Aerosol Research.

A mole-fraction-based thermodynamic model is used to represent available activity data, salt solubilities, and electrodynamic balance measurements for aqueous NaCl, Na2SO4, NaNO3 and their mixtures at 298.15 K. The results are presented as fitted ion-interaction parameters and equilibrium constants. These enable ion and solvent activities, and saturation with respect to five possible solid phases (NaCl, NaNO3, Na2SO4 . 10H(2)O, Na2SO4, and NaNO3 . Na2SO4 . H2O) to be calculated for all mixture compositions to relative humidities of less than or equal to 60\%, and to high degrees of supersaturation with respect to the dissolved salts. Extension of the model to other systems is discussed. (C) 1997 American Association for Aerosol Research.

Equilibrium water vapor pressures over supersaturated aqueous ammonium sulfate have been determined from 278.15 to 313.15 K using an electrodynamic balance. Partial molar enthalpies of water (L(1), to similar to 25 mol kg(-1)) and partial molar heat capacities (J(1), to similar to 8 mol kg(-1)) have been calculated from the measurements, together with enthalpies of solution, heat capacities, and boiling point elevations. The results-have been used to parameterize a mole-fraction-based activity coefficient model. Equilibrium constants for the reaction (NH4)(2)SO4(cr) reversible arrow 2NH(4(aq)(+)) + SO4(aq2-) have been evaluated from 373.15 K to the eutectic point (5.00 mol kg(-1), 254.21 K). The model satisfactorily represents water vapor pressures and saturation with respect to solid phases ice and ammonium sulfate from 253 to > 373.15 K and up to 8-10 mol kg(-1), and water vapor pressures from 278.15 to 313.15 K and up to similar to 25 mol kg(-1).

Equilibrium water vapor pressures over supersaturated aqueous ammonium sulfate have been determined from 278.15 to 313.15 K using an electrodynamic balance. Partial molar enthalpies of water (L(1), to similar to 25 mol kg(-1)) and partial molar heat capacities (J(1), to similar to 8 mol kg(-1)) have been calculated from the measurements, together with enthalpies of solution, heat capacities, and boiling point elevations. The results-have been used to parameterize a mole-fraction-based activity coefficient model. Equilibrium constants for the reaction (NH4)(2)SO4(cr) reversible arrow 2NH(4(aq)(+)) + SO4(aq2-) have been evaluated from 373.15 K to the eutectic point (5.00 mol kg(-1), 254.21 K). The model satisfactorily represents water vapor pressures and saturation with respect to solid phases ice and ammonium sulfate from 253 to > 373.15 K and up to 8-10 mol kg(-1), and water vapor pressures from 278.15 to 313.15 K and up to similar to 25 mol kg(-1).

Equilibrium water vapor pressures over supersaturated aqueous ammonium sulfate have been determined from 278.15 to 313.15 K using an electrodynamic balance. Partial molar enthalpies of water (L(1), to similar to 25 mol kg(-1)) and partial molar heat capacities (J(1), to similar to 8 mol kg(-1)) have been calculated from the measurements, together with enthalpies of solution, heat capacities, and boiling point elevations. The results-have been used to parameterize a mole-fraction-based activity coefficient model. Equilibrium constants for the reaction (NH4)(2)SO4(cr) reversible arrow 2NH(4(aq)(+)) + SO4(aq2-) have been evaluated from 373.15 K to the eutectic point (5.00 mol kg(-1), 254.21 K). The model satisfactorily represents water vapor pressures and saturation with respect to solid phases ice and ammonium sulfate from 253 to > 373.15 K and up to 8-10 mol kg(-1), and water vapor pressures from 278.15 to 313.15 K and up to similar to 25 mol kg(-1).