The System

The sources of data used to determine mixture parameters W, Q and U in the activity coefficient equations for this ternary (3 ion) system are listed in Table 4 of Clegg et al. (1998a). Fits of the model are described in section 3.5 of that paper. The following types of data were considered:

1. Solubilities of the solids NH4NO3(s) and ice in the ternary solution.
2. The activity coefficient ratio of the ions NH4⁺ and H⁺, from measurements of the stoichiometric acid dissociation constant of NH4⁺.
3. Vapour pressures of HNO3 and water (used for comparison only).

References: S. L. Clegg, P. Brimblecombe and A. S. Wexler (1998a) J. Phys. Chem. A 102, 2137-2154.

Weights

The values listed in the tables below are based upon those used in the fits of the model. However, they have been normalised for each type of measurement so that the maximum weight for any data point in each table is always unity. All solutions in which mHNO3 was greater than 25 mol kg^-1, or T greater than 308.15 K, were weighted zero in order to optimise agreement with data for lower acidities and low to moderate temperature. Other points given zero weight are those which either appear to be in error, or are used for comparison only (and were not fitted). Points with a weight of "-" are outside the temperature or concentration limits of the current model, and have not been assessed for accuracy.

The Data

The experimental data used to fit the activity coefficient model are listed in the tables below. Notes at the end of each one define the tabulated quantities, and identify the sources of the measurements.

(1) Solubilities of Solid Phases

     mNH4NO3      mHNO3        t    solid     ref.     weight  
      23.856      0.000      20.0    1      a(398)     0.04    
      20.959      1.761      20.0    1      a(398)     0.04    
      19.835      3.967      20.0    1      a(398)     0.04    
      18.703      6.802      20.0    1      a(398)     0.04    
      17.989     10.580      20.0    1      a(398)     0.04    
      19.124     15.875      20.0    1      a(398)     0.04    
      14.844      0.000       0.0    1      a(399)     0.04     
      11.490      3.087       0.0    1      a(399)     0.04     
      10.407      5.336       0.0    1      a(399)     0.04     
       9.686      7.489       0.0    1      a(399)     0.04     
       9.486      8.817       0.0    1      a(399)     0.04     
       9.697     10.425       0.0    1      a(399)     0.04     
       9.988     12.239       0.0    1      a(399)     0.04     
      10.818     14.717       0.0    1      a(399)     0.04     
      12.651     18.123       0.0    1      a(399)     0.04     
      14.974     22.401       0.0    1      a(399)     0.04     
      17.267     26.708       0.0    1      a(399)     0.0      
      33.570     49.444       0.0    1      a(399)     0.0                     
     136.858    170.960       0.0    1      a(399)     0.0                                    
      20.734      0.000      15.0    1      a(399)     0.04                                   
      19.983      0.291      15.0    1      a(399)     0.04                                   
      19.379      1.166      15.0    1      a(399)     0.04                                   
      17.074      3.133      15.0    1      a(399)     0.04                                   
      16.658      3.662      15.0    1      a(399)     0.04                                   
      15.064      6.867      15.0    1      a(399)     0.04                                   
      14.604      9.539      15.0    1      a(399)     0.04                                   
      15.968     13.440      15.0    1      a(399)     0.04                                   
      16.715     17.061      15.0    1      a(399)     0.04                                   
      21.303     24.890      15.0    1      a(399)     0.04                                   
      25.234     30.640      15.0    1      a(399)     0.0                                    
      63.553     75.899      15.0    1      a(399)     0.0                                    
     262.359    285.655      15.0    1      a(399)     0.0                                    
      29.430      0.000      30.0    1      a(399)     0.04                                   
      26.397      1.792      30.0    1      a(399)     0.04                                   
      24.946      4.475      30.0    1      a(399)     0.04                                   
      24.007      5.497      30.0    1      a(399)     0.04                                   
      23.154      7.617      30.0    1      a(399)     0.04                                   
      21.967      8.776      30.0    1      a(399)     0.04                                   
      23.228     11.917      30.0    1      a(399)     0.04                                   
      22.389     12.571      30.0    1      a(399)     0.04                                   
      24.140     16.692      30.0    1      a(399)     0.04                                   
      26.375     21.160      30.0    1      a(399)     0.04                                   
      43.682     42.814      30.0    1      a(399)     0.0                                    
      71.591     71.503      30.0    1      a(399)     0.0                                    
     315.739    304.410      30.0    1      a(399)     0.0                                    
      66.081      0.000      75.0    1      a(399)     0.0                                    
      68.204     15.047      75.0    1      a(399)     0.0                                    
      73.526     20.813      75.0    1      a(399)     0.0                                    
     136.016     67.318      75.0    1      a(399)     0.0                                    
     521.595    313.427      75.0    1      a(399)     0.0                                    
      25.939      0.000      25.0    1      a(400)     0.04                                   
      20.426      6.918      25.0    1      a(400)     0.04                                   
      20.642     14.051      25.0    1      a(400)     0.04                                   
      41.589     43.809      25.0    1      a(400)     0.0                                    
      78.855     84.406      25.0    1      a(400)     0.0                                    
    2803.188   2747.680      25.0    1      a(400)     0.0                                    
     264.063    528.918      25.0    1      a(400)     0.0                                    
      42.633      0.000      50.0    1      a(401)     0.0           
      42.308      0.000      50.0    1      a(401)     0.0           
      33.382     14.719      50.0    1      a(401)     0.0                                    
      43.718     22.521      50.0    1      a(401)     0.0                                    
      40.901     28.659      50.0    1      a(401)     0.0          
     612.816    497.358      50.0    1      a(401)     0.0          
     732.186    589.449      50.0    1      a(401)     0.0          
      11.186      0.000     -10.0    1      b          0.04          
      10.069      1.003     -10.0    1      b          0.04          
       8.916      2.346     -10.0    1      b          0.04            
       7.371      5.070     -10.0    1      b          0.04            
       7.006      8.094     -10.0    1      b          0.04            
      11.833     22.533     -10.0    1      b          0.04            
      15.088     27.865     -10.0    1      b          0.0             
      18.665     33.621     -10.0    1      b          0.0             
      19.868     35.116     -10.0    1      b          0.0             
      40.981     64.432     -10.0    1      b          0.0             
      53.946     81.086     -10.0    1      b          0.0             
      53.946     81.086     -10.0    2      b          0.0             
      39.587     68.334     -10.0    2      b          0.0          
      34.352     68.271     -10.0    2      b          0.0             
      26.716     68.273     -10.0    2      b          0.0             
      25.409     68.543     -10.0    2      b          0.0             
      16.028     78.023     -10.0    2      b          0.0             
      15.946    110.546     -10.0    2      b          0.0             
      15.233      0.000       0.0    1      b          0.04            
      13.951      0.886       0.0    1      b          0.04            
      12.334      2.250       0.0    1      b          0.04            
      10.450      4.737       0.0    1      b          0.04            
       9.644      8.624       0.0    1      b          0.04            
       9.759     11.074       0.0    1      b          0.04            
      12.089     17.725       0.0    1      b          0.04            
      18.323     28.358       0.0    1      b          0.0             
      33.193     48.333       0.0    1      b          0.0             
      36.834     52.841       0.0    1      b          0.0             
      54.472     74.112       0.0    1      b          0.0             
      77.165    105.003       0.0    1      b          0.0             
      51.413     86.579       0.0    2      b          0.0             
      30.016     83.999       0.0    2      b          0.0             
      26.652     92.223       0.0    2      b          0.0             
      23.018    115.192       0.0    2      b          0.0             
      26.781      0.000      25.0    1      b          0.04            
      22.867      3.422      25.0    1      b          0.04            
      19.964     11.285      25.0    1      b          0.04            
      24.677     21.843      25.0    1      b          0.04            
      29.823     29.161      25.0    1      b          0.0             
      41.511     44.675      25.0    1      b          0.0             
      68.839     74.598      25.0    1      b          0.0             
      32.463      0.000      35.0    1      b          0.04            
      28.035      5.809      35.0    1      b          0.04            
      27.888     16.323      35.0    1      b          0.04            
      35.182     27.605      35.0    1      b          0.0             
     155.601    145.521      35.0    1      b          0.0             
      48.154      0.000      55.0    1      b          0.0             
      45.155      3.660      55.0    1      b          0.0             
      45.101     13.277      55.0    1      b          0.0             
      54.831     27.917      55.0    1      b          0.0             
      53.633     27.761      55.0    1      b          0.0             
      63.641     40.215      55.0    1      b          0.0             
      74.750      0.000      80.0    1      b          0.0             
      85.449     17.030      80.0    1      b          0.0             
      94.986     21.381      80.0    1      b          0.0             
      82.803      0.000      86.0    1      b          0.0             
      87.809      5.725      86.0    1      b          0.0             
      99.293     17.497      86.0    1      b          0.0             
     105.479      0.000     100.0    1      b          0.0             
     119.968      4.049     100.0    1      b          0.0             
     169.631     28.389     100.0    1      b          0.0             
     184.535     36.180     100.0    1      b          0.0             
     334.635    117.850     100.0    1      b          0.0             
     329.198    359.450      17.0    1      b          0.0             
     321.010    358.125      14.6    1      b          0.0             
     312.453    357.608      11.0    1      b          0.0             
     294.889    358.117       9.8    1      b          0.0             
     268.268    358.213      13.2    2      b          0.0             
     237.000    358.386      16.1    2      b          0.0             
     209.061    358.477      18.3    2      b          0.0             
     147.660    359.320      19.0    2      b          0.0             
     105.152    359.205      16.2    2      b          0.0             
      60.337    358.332       0.6    2      b          0.0             
      48.223    358.857      -7.8    2      b          0.0             
      35.629    358.707     -19.8    2      b          0.0             
      71.145     95.663       2.4    1      b          0.0             
      69.928     95.679       0.2    1      b          0.0             
      67.741     95.713      -4.4    1      b          0.0             
      65.035     95.762      -5.6    2      b          0.0             
      60.012     95.707      -3.8    2      b          0.0             
      43.085     95.751       0.3    2      b          0.0             
      29.711     95.681       0.6    2      b          0.0             
      18.852     95.706      -4.8    2      b          0.0             
      14.249     95.685     -10.4    2      b          0.0             
      10.623     95.694     -17.2    2      b          0.0             
       6.929     95.736     -28.5    2      b          0.0             
      56.592     72.383      10.5    1      b          0.0             
      52.275     72.404       3.0    1      b          0.0             
      46.641     72.373      -8.5    1      b          0.0             
      43.478     72.390     -13.8    2      b          0.0             
      42.296     72.351     -13.6    2      b          0.0             
      39.263     72.374     -13.0    2      b          0.0             
      32.379     72.339     -11.3    2      b          0.0             
      26.953     72.344     -10.4    2      b          0.0             
      22.935     72.376     -10.6    2      b          0.0             
      17.531     72.375     -12.2    2      b          0.0             
      10.006     72.373     -19.2    2      b          0.0             
       6.811     72.363     -26.2    2      b          0.0             
      38.302     62.842     -12.5    1      b          0.0             
      37.232     62.786     -16.0    1      b          0.0             
      35.273     62.824     -17.8    2      b          0.0             
      31.061     62.841     -16.6    2      b          0.0             
      22.086     62.870     -15.0    2      b          0.0             
      13.858     62.824     -16.8    2      b          0.0             
       7.240     62.855     -25.0    2      b          0.0             
      25.376     48.899     -24.0    1      b          0.0 
      24.203     48.869     -28.0    1      b          0.0 
      23.916     48.894     -28.7    1      b          0.0 
      23.170     48.881     -28.6    2      b          0.0 
      21.535     48.880     -27.5    2      b          0.0             
      15.981     48.876     -26.2    2      b          0.0             
      12.386     48.873     -27.0    2      b          0.0             
       8.817     48.862     -28.6    2      b          0.0             
      17.018     35.544     -25.0    1      b          0.0             
      15.863     35.562     -31.5    1      b          0.0             
      15.340     35.554     -34.0    1      b          0.0             
      14.517     35.539     -36.0    2      b          0.0             
      13.235     35.547     -35.5    2      b          0.0             
       7.831     35.550     -36.0    2      b          0.0             
       9.159      0.000     -16.9    1      b          0.02            
       9.159      0.000     -16.9    0      b          1.0       
       7.495      0.967     -18.4    1      b          0.02            
       7.495      0.967     -18.4    0      b          1.0       
       7.122      1.397     -18.9    1      b          0.02            
       7.122      1.397     -18.9    0      b          1.0       
       6.331      1.930     -19.9    1      b          0.02            
       6.331      1.930     -19.9    0      b          1.0       
       5.456      2.709     -21.6    1      b          0.02            
       5.456      2.709     -21.6    0      b          1.0       
       4.388      3.903     -24.7    1      b          0.02            
       4.388      3.903     -24.7    0      b          1.0       
       3.318      5.462     -29.7    1      b          0.02            
       3.318      5.462     -29.7    0      b          1.0       
       1.912      7.756     -45.5    1      b          0.02            
       1.912      7.756     -45.5    0      b          1.0       
       1.912      7.756     -45.5    3      b          0.0             
       8.2838     0         -15.6    0      b          1.0                   
       7.4672     0         -14.4    0      b          1.0           
       4.6161     0         -10.6    0      b          1.0           
       3.1263     0          -7.9    0      b          1.0           
       2.1051     0          -5.5    0      b          1.0           
       1.0643     0          -3.0    0      b          1.0           
       6.082      1.554     -17.5    0      b          1.0       
       4.260      1.089     -13.1    0      b          1.0       
       2.681      0.685      -8.9    0      b          1.0       
       1.575      0.402      -5.6    0      b          1.0       
       3.605      3.219     -20.0    0      b          1.0       
       2.596      2.316     -15.0    0      b          1.0       
       1.754      1.565     -10.3    0      b          1.0       
       1.144      1.022      -6.8    0      b          1.0       
       0.619      0.552      -3.6    0      b          1.0       
       3.599      4.917     -28.0    0      b          1.0       
       2.820      3.852     -21.7    0      b          1.0       
       2.095      2.862     -15.8    0      b          1.0       
       1.567      2.140     -12.0    0      b          1.0       
       1.143      1.564      -8.7    0      b          1.0       
       0.795      1.087      -6.2    0      b          1.0       
       0.514      0.703      -4.0    0      b          1.0       
       0.298      0.406      -2.4    0      b          1.0       
       1.808      6.580     -35.5    0      b          1.0       
       1.393      5.068     -26.3    0      b          1.0       
       1.098      3.992     -19.7    0      b          1.0       
       0.791      2.876     -13.6    0      b          1.0       
       0.497      1.805      -8.3    0      b          1.0       
       0.271      0.984      -4.5    0      b          1.0       
       0.000      6.721     -34.3    0      b          1.0       
       0.000      5.341     -25.2    0      b          1.0       
       0.000      4.305     -19.2    0      b          1.0       
       0.000      3.012     -12.5    0      b          1.0       
       0.000      1.763      -6.8    0      b          1.0       

Notes and References

• Prefix m denotes molality; t - experimental temperature (^oC); solid - identity of the solid which the solution is saturated with respect to; ref. - source of data; weight - the weight given to the data point in the fit of the model (normalised).
• Solids: 0 = ice, 1 = NH4NO3(s), 2 = NH4NO3.2HNO3(s), 3 = HNO3.3HNO3(s). The identities of solids in tables 398 and 399 of reference (a) have been inferred from the data.
• Sources: a - H. L. Silcock, Solubilities of Inorganic and Organic Compounds, Vol. 3, Pergamon, Oxford, 1979, (the table numbers are given in parentheses); b - N. S. Kurnakov and M. I. Ravitch (1933) Izv. Inst. Fiz-Khim. Anal., Akad. Nauk SSSR 6, 169-184.

(2) The Activity Coefficient Ratio f [NH4]/f [H]

     mNH4NO3      mHNO3      t      ratio   ref.      weight  
       0.51        0.0     25.0     0.883    c         1.0   
       1.06        0.0     25.0     0.753    c         1.0   
       1.62        0.0     25.0     0.658    c         1.0   
       2.22        0.0     25.0     0.574    c         1.0   
       2.85        0.0     25.0     0.502    c         1.0   
       3.54        0.0     25.0     0.448    c         1.0   
       4.23        0.0     25.0     0.392    c         1.0   
       5.01        0.0     25.0     0.343    c         1.0   
       5.83        0.0     25.0     0.308    c         1.0   
       6.70        0.0     25.0     0.270    c         1.0   
       7.62        0.0     25.0     0.249    c         1.0   
       8.61        0.0     25.0     0.220    c         1.0   
       9.66        0.0     25.0     0.186    c         1.0   
      10.82        0.0     25.0     0.173    c         1.0   

Notes and References

• Prefix m denotes molality; t - the experimental temperature (^oC); ratio - value of f [NH4]/f [H], where f is the mole fraction activity coefficient of the ion for a reference state of infinite dilution in water (see also note below); ref. - source of data; weight - the weight given to the data point in the fit of the model (normalised).
• The stoichiometric acid dissociation constants measured by Maeda and Kato (1995) are equivalent to Ka x g[NH4]/(g[H] x g[NH3]), where Ka is the thermodynamic acid dissociation constant of NH4⁺, and g is the molal activity coefficient of the ion. Using Ka equal to 5.6937E-10 mol kg^-1, and taking values of g[NH3] in aqueous NH4NO3 also determined by Maeda and Kato, the ratio of the two cation activity coefficients was obtained from the stoichiometric dissociation constant. Values of the ratio (listed in the table) are the same on both the mole fraction and molality scales.
• Sources: c - M. Maeda and K. Kato (1995) J. Chem. Eng. Data 40, 253-256.

(3) Equilibrium Vapour Pressures of HNO3 and H2O

    mNH4NO3     mHNO3       t     pHNO3     pH2O   ref.      weight 
     2.014     16.087     25.0  4.605E-4           d         0.0
     2.231     19.538     25.0  8.553E-4           d         0.0
     4.027     16.087     25.0  4.211E-4           d         0.0    
     4.462     19.538     25.0  7.237E-4           d         0.0 
     2.014     16.087     25.0            0.01253  d         0.0 
     2.231     19.538     25.0            0.01108  d         0.0 
     4.027     16.087     25.0            0.01239  d         0.0 
     4.462     19.538     25.0            0.01096  d         0.0 

Notes and References

• Prefix m denotes molality, and p partial pressure (atm); t - experimental temperature (^oC); ref. - source of data; weight - the weight given to the data point in the fit of the model (normalised).
• These data were used for comparison only, and were not included in the fit of the activity coefficient model parameters.
• Sources: d - R. Flatt and F. Benguerel (1962) Helvetica Chim. Acta 45, 1772-1776.