The System

The sources of data used to determine mixture parameters W, Q and U in the activity coefficient equations for this system are listed in Table 7 of Clegg et al. (1998a). Fits of the model are described in section 3.9 of that paper. The following types of data were used:

1. Solubilities of solids NH4NO3(s), NH4NO3.NH4HSO4(s), and NH4HSO4(s) in the ternary solutions.

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 a data point in each table is always unity. 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 below. Notes at the end define the tabulated quantities, and identify the sources of the measurements.

(1) Solubilities of Solid Phases

 mH2SO4     m(NH4)2SO4    mNH4NO3       t       solid    ref.   weight 
  2.228        2.228      27.199       25.0       1       a      1.0   
  5.035        5.035      29.814       25.0       1       a      1.0   
  8.882        8.882      31.757       25.0       1       a      1.0   
 12.765       12.765      27.439       25.0       2       a      0.5   
 11.466       11.466      21.695       25.0       2       a      0.5   
 11.807       11.807      20.003       25.0       2       a      0.5   
 18.375       18.375      24.537       25.0       2       a      0.5   
 19.119       19.119      20.500       25.0       3       a      0.0   
 16.890       16.890      12.420       25.0       3       a      0.0   
 13.540       13.540       4.594       25.0       3       a      0.0   
 12.421       12.421      24.842       20.0       2       b      0.5   
 14.075       14.075      28.150       30.0       2       b      0.5   
 16.996       16.996      33.992       40.0       2       b      0.5   
 21.383       21.383      42.766       50.0       2       b      0.5   
 32.061       32.061      64.122       60.0       2       b       - 

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: 1 = NH4NO3(s), 2 = NH4NO3.NH4HSO4(s), 3 - NH4HSO4(s).
• Sources: a - H. L. Silcock, Solubilities of Inorganic and Organic Compounds, Vol. 3, Pergamon, Oxford, 1979; b - A. Seidell, Solubilities of Inorganic and Metal Organic Compounds, 2 Vols., 4th Edn., ed. W. F. Linke, American Chemical Society, Washington, DC, 1958-1965.