Equilibrium water partial pressures and salt solubilities in aqueous NH{sub 4}HSO{sub 4} to low temperatures
- Chinese Academy of Sciences, Xi`an (China). Inst. of Salt Lakes
- Univ. of East Anglia, Norwich (United Kingdom). School of Environmental Sciences
Acidic ammonium sulfate aerosols in the troposphere form cloud condensation nuclei, affect visibility, and are also an important component of urban aerosols. Equilibrium water partial pressures (pH{sub 2}O) above 3.69{sub 5}, 5.67{sub 2}, and 8.65{sub 1} mol kg{sup {minus}1} NH{sub 4}HSO{sub 4(aq)}, and 10.19 mol kg{sup {minus}1} H{sub 2}SO{sub 4(aq)}, have been determined using a capacitance manometer over the temperature ranges 288.1{sub 1}--239.5{sub 6} K and 298.1{sub 2}--238.5{sub 2} K, respectively. Measured pH{sub 2}O above the aqueous H{sub 2}SO{sub 4} solution agree with values calculated using the model of Clegg et al. to within +5.3% to {minus}2.8% at all temperatures. Results for the NH{sub 4}HSO{sub 4(aq)} solutions are also consistent with calculated pH{sub 2}O, with deviations of +0.45% to +6.27% (measured -- calculated) for all data. The formation of solids was observed in the NH{sub 4}HSO{sub 4(aq)} solutions at the following temperatures: 258.0{sub 6} {+-} 0.1 K [3.69{sub 5} mol kg{sup {minus}1}], 246.4{sub 7} {+-} 0.1 K [5.67{sub 2} mol kg{sup {minus}1}], and 261.0{sub 1} {+-} 0.1 K [8.65{sub 1} mol kg{sup {minus}1}]. The data are consistent with predictions of ice precipitation in the 3.69{sub 5} mol kg{sup {minus}1} test solution, letovicite ((NH{sub 4}){sub 3}H(SO{sub 4}){sub 2(cr)}) in the 8.65{sub 1} mol kg{sup {minus}1} solution, and both ice and letovicite in the 5.67{sub 2} mol kg{sup {minus}1} solution. The liquid-phase compositions of the solutions containing precipitates are calculated for different temperatures. The results of the experiments are compared with solubility data from other studies and with model predictions of solid/liquid equilibrium for NH{sub 4}HSO{sub 4}-H{sub 2}SO{sub 4}-H{sub 2}O mixtures to low temperature over a wide range of composition.
- OSTI ID:
- 355565
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Vol. 103, Issue 19; Other Information: PBD: 13 May 1999
- Country of Publication:
- United States
- Language:
- English
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