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Water activities of NH₄NO₃/(NH₄)₂SO₄ solutions

Chan, Chak K. and Flagan, Richard C. and Seinfeld, John H. (1992) Water activities of NH₄NO₃/(NH₄)₂SO₄ solutions. Atmospheric Environment Part A-General Topics, 26 (9). pp. 1661-1673. ISSN 0960-1686. doi:10.1016/0960-1686(92)90065-S.

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Water activities for mixed ammonium nitrate/ammonium sulfate solutions at relative humidities of 0.35–0.75 were measured using a spherical void electrodynamic balance. The concentrations of singly levitated droplets of nitrate to sulfate mole ratio of n = 1/5, 1/3, 1/2, 1, 2 and 4 in equilibrium with an ambient environment of prescribed relative humidity were measured. To avoid uncertainty in determining the composition of the solid particles, solution properties were determined relative to the known properties at about 80% relative humidity. The concentration of this reference state was estimated by three models of mixed electrolyte solutions, the Zdanovskii-Stokes-Robinson (ZSR), the Kusik and Meissner (KM) and the Pitzer models. The measured total mass fraction of solute of the mixed solutions differed by less than 0.5% when different models were used to calculate the reference state concentration. The water activity data were obtained at ionic strengths as high as 108 molal and used to evaluate predictions from these three models. For n = 1/5 and 1/3, deviations of model predictions from experimental data are within 2%. Generally, predictions of the ZSR model are most consistent with our data. Maximum deviations occur at n=2; 6% for ZSR, 8% for KM and 5% for Pitzer. The deviations can be attributed to binary and ternary solute-solute interactions that the ZSR, KM and elementary version of the Pitzer models do not consider. However, no simple characterization of the interaction parameters is possible; they seem to be strong functions of the fractional ionic strength of the solute and the total ionic strength of the solutions.

Item Type:Article
Related URLs:
URLURL TypeDescription
Chan, Chak K.0000-0001-9687-8771
Flagan, Richard C.0000-0001-5690-770X
Seinfeld, John H.0000-0003-1344-4068
Alternate Title:Water activities of NH4NO3/(NH4)2SO4 solutions
Additional Information:© 1992 Elsevier. (First received 27 July 1991 and in final form 12 November 1991) This work was supported by National Science Foundation grant ATM-9003186.
Funding AgencyGrant Number
Subject Keywords:Water activities, ammonium nitrate, ammonium sulfate
Issue or Number:9
Record Number:CaltechAUTHORS:20150805-111952094
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Official Citation:Chak K. Chan, Richard C. Flagan, John H. Seinfeld, Water activities of NH4NO3/(NH4)2SO4 solutions, Atmospheric Environment. Part A. General Topics, Volume 26, Issue 9, June 1992, Pages 1661-1673, ISSN 0960-1686,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59226
Deposited By: Irina Meininger
Deposited On:09 Dec 2015 21:41
Last Modified:19 Apr 2023 23:03

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