Aqueous H₂SO₄: Solid/Liquid Equilibrium

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

We also tabulate data from the following references. Gillespie et al. (1950) cite a number of very early studies not included here.

• R. J. Gillespie, D. Hughes, and C. K. Ingold (1950) J. Chem. Soc. 2473-2492.
• R. J. Gillespie (1950) J. Chem. Soc. 2493-2503.
• L. P. Hammett and A. J. Deyrup (1933) J. Amer. Chem. Soc. 55, 1900-1909.

1.  Saturation of H2SO4 - H2O Mixtures with Respect to H2SO4(s) and H2SO4 · H2O(s)

    wt%        θ      solid  series   ref.   
  99.986    0.47700     0      1       a
  99.898    0.47200     0      1       a
  99.897    0.46600     0      1       a
  99.816    0.98600     0      1       a
  99.557    2.57000     0      1       a
  99.276    4.20000     0      2       a
  99.017    5.78000     0      2       a
  98.707    7.67000     0      2       a
  98.378    9.77000     0      2       a
  93.806   44.04000     0      3       a
  93.835   43.75000     0      3       a
  94.010   42.20000     0      3       a
  94.260   39.93000     0      3       a
  94.513   37.70000     0      3       a
  95.062   33.29000     0      3       a
  95.311   31.25000     0      3       a
  95.591   29.08000     0      3       a
  95.801   27.26000     0      3       a
  96.065   25.20000     0      3       a
  96.222   24.32000     0      3       a
  96.622   21.47000     0      3       a
  97.090   18.19000     0      3       a
  97.490   15.50000     0      3       a
  97.847   13.16000     0      3       a
  93.382   39.96000     1      4       a
  93.256   38.56000     1      4       a
  92.412   31.07000     1      4       a
  92.301   30.13000     1      4       a
  92.214   29.40000     1      4       a
  91.913   27.01000     1      4       a
  91.583   24.49000     1      4       a
  91.299   22.47000     1      4       a
  90.832   19.35000     1      4       a
  90.406   16.77000     1      4       a
  90.288   16.07000     1      4       a
  89.926   14.07000     1      4       a
  89.482   11.79000     1      4       a
  88.890    9.10000     1      4       a
  88.420    7.24000     1      4       a
  87.748    5.01000     1      5       a
  87.338    3.80000     1      5       a
  86.896    2.71000     1      5       a
  86.542    1.98300     1      5       a
  86.514    1.91900     1      5       a
  86.113    1.23500     1      5       a
  85.794    0.79700     1      5       a
  85.488    0.46100     1      5       a
  85.189    0.23300     1      5       a                                                      
  84.909    0.08740     1      5       a                                                      
  84.895    0.08210     1      5       a                                                      
  84.880    0.07620     1      5       a                                                      
  84.828    0.05620     1      5       a                                                      
  84.775    0.04080     1      5       a                                                      
  84.723    0.02770     1      5       a                                                      
  84.672    0.01680     1      5       a                                                      
  84.620    0.00870     1      5       a                                                      
  84.570    0.00350     1      5       a                                                      
  84.518    0.00040     1      5       a                                                      
  84.469    0.00020     1      5       a                                                      
  84.419    0.00200     1      5       a                                                      
  84.371    0.00590     1      5       a                                                      
  84.323    0.01170     1      5       a                                                      
  84.276    0.02040     1      5       a                                                      
  84.006    0.10020     1      5       a                                                      
  83.435    0.49700     1      5       a                                                      
  82.824    1.23700     1      5       a                                                      
  82.412    1.92200     1      5       a                                                      
  81.783    3.24100     1      5       a                                                      
  81.850    3.07700     1      6       a                                                      
  81.888    3.01100     1      6       a                                                      
  80.947    5.56000     1      6       a                                                      
  80.154    8.31000     1      6       a                                                      
  79.446   11.19000     1      6       a                                                      
  78.921   13.63000     1      6       a                                                      
  78.329   16.52000     1      6       a                                                      
  77.745   19.77000     1      6       a                                                      
  76.643   26.51000     1      6       a                                                      
  76.193   29.55000     1      6       a                                                      
  75.990   30.99000     1      6       a                                                      
  75.786   32.47000     1      6       a                                                      
  75.339   35.87000     1      6       a                                                      
  74.788   40.11000     1      7       a                                                      
  74.309   44.17000     1      7       a                                                      
  74.410   43.29000     1      7       a                                                      
  74.550   42.25000     1      7       a                                                      
 100.0960   0.28800     0      8       a                                                      
 100.0860   0.24800     0      8       a                                                      
 100.0760   0.21400     0      8       a                                                      
 100.0570   0.14400     0      8       a                                                      
 100.0386   0.07840     0      8       a                                                      
 100.0270   0.04400     0      8       a                                                      
 100.0193   0.02490     0      8       a                                                      
 100.0157   0.01710     0      8       a                                                      
 100.0121   0.01050     0      8       a                                                      
 100.0084   0.00530     0      8       a                                                      
 100.0047   0.00180     0      8       a                                                      
 100.0011   0.00010     0      8       a                                                      
  99.9974   0.00050     0      8       a                                                      
  99.9936   0.00310     0      8       a                                                      
  99.9902   0.00840     0      8       a                                                      
  99.9866   0.01490     0      8       a                                                      
  99.9830   0.02340     0      8       a                                                      
  99.9759   0.04480     0      8       a                                                      
  99.9689   0.07200     0      8       a                                                      
  99.9615   0.10440     0      8       a                                                      
  99.9480   0.17360     0      8       a                                                      
  99.9310   0.26800     0      8       a                                                      
  99.9140   0.36700     0      8       a                                                      
  99.8830   0.56500     0      8       a                                                      
  99.8500   0.76800     0      8       a                                                      
  99.8190   0.96400     0      8       a                                                      
  99.7870   1.15500     0      8       a                                                      
  99.7910   1.15500     0      8       a                                                      
  99.7910   1.15500     0      8       a                                                      
  99.7870   1.15500     0      8       a                                                      

Notes and References

• Key: wt% - weight percent of H2SO4 in the liquid phase; θ - the freezing point depression (in ^oC) with respect to the melting point of the pure solid; solids - 0, H2SO4; 1, H2SO4 · H2O; ref. - source of data.
• Source: a - J. E. Kunzler and W. F. Giauque (1952) J.Amer. Chem. Soc. 74, 5271-5274.
• Th weight percentage of H2SO4 is equal to (98.082/80.066) × (wt.SO3 × 100)/(wt.SO3 + wt.H2O). Values of >100% occur for mixtures containing an excess of SO3 over H2O. Molar masses of 98.082 (H2SO4) and 18.016 (water) were used by Kunzler and Giauque.
• The melting points of the solids are: 283.46 K (H2SO4), and 283.63 K (H2SO4 · H2O) (W. F. Giauque et al. (1960) J. Amer. Chem. Soc. 82, 62-70).

2.  Saturation of H2SO4 - H2O Mixtures with Respect to Solid Sulphuric Acid and its Hydrates

     wt%      solid      t        ref.          wt%       solid       t       ref.         
    29.20        6     -61.98      a            69.65        1       8.10      a       
    30.65        4     -73.10      a            70.90        1       5.27      a       
    29.55        6     -61.33      a            71.79        1       2.40      a       
    30.85        6     -58.67      a            72.35        1       0.00      a       
    31.62        6     -57.12      a            72.65        1      -1.36      a       
    33.06        6     -55.74      a            73.33        1      -4.64      a       
    34.62        6     -53.73      a            73.98        1      -9.18      a       
    34.62        4     -53.73      a            74.81        1     -15.32      a       
    31.27        4     -71.39      a            75.41        1     -20.72      a       
    31.49        4     -69.91      a            75.57        1     -23.17      a       
    31.74        4     -68.41      a            76.02        1     -28.24      a       
    32.72        4     -63.27      a            76.43        1     -33.84      a       
    32.29        4     -65.29      a            76.55        1     -34.86      a       
    33.62        4     -58.59      a            76.55        0     -34.86      a       
    34.03        4     -56.72      a            76.58        0     -34.61      a       
    34.81        4     -53.48      a            76.91        0     -28.94      a       
    35.50        4     -50.95      a            77.36        0     -24.46      a       
    36.25        4     -48.47      a            77.75        0     -19.63      a       
    37.71        4     -43.65      a            78.39        0     -14.91      a       
    38.54        4     -41.49      a            78.74        0      -9.95      a       
    38.98        4     -39.86      a            79.37        0      -5.43      a       
    40.38        4     -36.63      a            79.83        0      -1.98      a       
    41.48        4     -34.20      a            80.33        0       0.46      a       
    43.33        4     -30.97      a            80.56        0       2.80      a       
    44.21        4     -29.89      a            80.87        0       4.97      a       
    45.20        4     -29.10      a            81.51        0       9.17      a       
    46.01        4     -28.62      a            81.62        0      10.372     a       
    47.05        4     -28.63      a            81.65        0      10.32      a       
    47.42        4     -28.41      a            81.69        0      10.22      a       
    49.01        4     -29.37      a            81.77        0       9.66      a       
    49.60        4     -29.86      a            81.80        0       8.36      a       
    51.25        4     -32.66      a            82.04        0       8.36      a       
    52.62        4     -36.60      a            82.67        0       5.51      a       
    54.10        4     -41.66      a            82.86        0       3.56      a       
    55.06        4     -46.14      a            83.00        0       1.87      a       
    55.97        4     -51.80      a            83.36        0       0.78      a       
    52.81        4     -36.56      a            83.53        0      -1.97      a       
    52.81        3     -36.56      a            84.16        0      -6.06      a       
    55.35        4     -47.46      a            84.44        0      -6.53      a       
    55.35        2     -47.46      a            84.45        0      -9.96      a       
    53.62        3     -36.98      a            84.50        0     -10.15      a       
    55.08        3     -38.38      a            84.50       10     -10.15      a       
    56.31        3     -41.22      a            84.58       10      -9.15      a       
    57.15        3     -43.50      a            84.66       10      -8.77      a       
    57.87        3     -46.29      a            84.81       10      -4.48      a       
    58.53        3     -49.35      a            84.87       10      -4.12      a       
    56.90        3     -42.70      a            84.83       10      -3.44      a       
    56.90        2     -42.70      a            85.53       10      -1.20      a       
    59.10        3     -52.85      a            85.33       10       1.37      a       
    59.10        1     -52.85      a            85.47       10       3.23      a       
    55.44        2     -47.01      a            85.92       10       9.07      a       
    56.09        2     -44.18      a            86.07       10      12.16      a       
    56.93        2     -42.76      a            86.09       10       9.68      a       
    58.11        2     -40.45      a            86.28       10      14.27      a       
    59.04        2     -39.72      a            86.81       10      19.44      a       
    59.70        2     -39.61      a            86.85       10      19.23      a       
    60.15        2     -39.87      a            87.46       10      24.50      a       
                                                87.46       10      24.31      a       
                                                88.80       10      33.51      a       
                                                89.08       10      34.42      a       
                                                89.60       10      34.66      a       
                                                89.65       10      34.90      a       
                                                89.81       10      34.85      a       
                                                89.86       10      35.15      a       
                                                90.58       10      34.07      a       
                                                90.85       10      33.12      a       
                                                91.11       10      30.09      a       
                                                91.61       10      26.37      a       
                                                92.74       10      16.11      a       
                                                93.27       10      10.04      a       
                                                93.11       10       5.32      a       
                                                93.33       10       3.31      a       
                                                93.69       10       2.24      a       

Notes and References

• Key: wt% - weight percent of SO3 in the liquid phase; t - the freezing point (in ^oC); solids: -1, ice; 0, H2SO4; 1, H2SO4 · H2O; 2, H2SO4 · 2H2O; 3, H2SO4 · 3H2O; 4, H2SO4 · 4H2O; 6, H2SO4 · 6.5H2O; 10, H2S2O7.
• Source: a - C. M. Gable, H. F. Betz, and S. H. Maron (1950) J.Amer. Chem. Soc. 72, 1445-1448.
• The hemi-hexahydrate is listed by Gable et al. as being the hexahydrate. The formula was later shown to be the hemi-hexahydrate by Hornung et al. (E. W. Hornung, T. E. Brackett, and W. F. Giauque (1956) J. Amer. Chem. Soc. 78, 5747-5751).

3.  Saturation of H2SO4 - H2O Mixtures with Respect to Solid Sulphuric Acid

   wtH2O   wtH2SO4   solid   series
   0.0045   26.79      0       26       10.351     a
   0.0362   26.79      0       26       10.299     a
   0.0074   18.07      0       66       10.340     a
   0.0436   18.07      0       66       10.224     a
   0.0881   18.07      0       66       10.032     a
   0.1307   18.07      0       66        9.821     a
   0.1857   18.07      0       66        9.585     a
   0.2307   18.07      0       66        9.353     a
   0.2746   18.07      0       66        9.127     a
   0.3198   18.07      0       66        8.878     a
   0.3657   18.07      0       66        8.644     a
   0.4076   18.07      0       66        8.421     a
   0.0378   27.20      0       67       10.294     a
   0.0815   27.20      0       67       10.129     a
   0.1265   27.20      0       67        9.928     a
   0.1671   27.20      0       67        9.737     a
   0.2071   27.20      0       67        9.537     a
   0.2504   27.20      0       67        9.330     a
   0.3037   27.20      0       67        9.117     a
   0.3444   27.20      0       67        8.914     a
   0.3872   27.20      0       67        8.710     a
   0.0141   29.64      0       73       10.350     a
   0.0485   29.64      0       73       10.284     a
   0.1504   29.64      0       73        9.855     a
   0.2149   29.64      0       73        9.549     a
   0.2602   29.64      0       73        9.346     a
   0.3272   29.64      0       73        9.013     a
   0.0334   25.58      0       76       10.282     a
   0.0673   25.58      0       76       10.181     a
   0.1343   25.58      0       76        9.875     a
   0.1935   25.58      0       76        9.579     a
   0.2587   25.58      0       76        9.264     a
   0.3231   25.58      0       76        8.943     a
   0.3881   25.58      0       76        8.656     a
   0.1150   20.18      0       79        9.939     a
   0.1517   20.18      0       79        9.778     a
   0.2209   20.18      0       79        9.427     a
   0.2853   20.18      0       79        9.087     a
   0.3535   20.18      0       79        8.732     a
   0.4218   20.18      0       79        8.380     a
   0.0237   25.99      0       80       10.322     a
   0.0564   25.99      0       80       10.219     a
   0.1248   25.99      0       80        9.914     a
   0.1911   25.99      0       80        9.592     a
   0.0114   27.04      0       90       10.343     a
   0.0459   27.04      0       90       10.263     a
   0.1153   27.04      0       90        9.971     a
   0.1839   27.04      0       90        9.645     a
   0.2739   27.04      0       90        9.202     a
   0.3478   27.04      0       90        8.840     a
   0.4158   27.04      0       90        8.513     a
   0.4858   27.04      0       90        8.180     a
   0.5556   27.04      0       90        7.832     a
   0.0310   29.65      0      102       10.329     a
   0.0046   31.23      0      103       10.344     a

Notes and References

• Key: wtH2O - grams of H2O in the liquid phase; wtH2SO4 - grams of H2SO4 in the liquid phase; solid - 0, H2SO4; t - temperature (^oC); ref. - source of data.
• Source: a - R. J. Gillespie (1950) J. Chem. Soc., 2493-2503.

4.  Saturation of H2SO4 - H2O Mixtures with Respect to Solid Sulphuric Acid

   wtH2O    wtH2SO4    solid  series    BT     ref.   
   0.0        53.7       0      1     0.438     a                                      
   0.0733     53.7       0      1     1.033     a                                      
   0.1470     53.7       0      1     1.612     a                                      
   0.2065     53.7       0      1     2.070     a                                      
   0.2939     53.7       0      1     2.617     a                                      
   0.3168     53.7       0      1     2.447     a                                      
   0.3478     53.7       0      1     2.103     a                                      
   0.3730     53.7       0      1     1.799     a                                      
   0.3882     53.7       0      1     1.615     a                                      
   0.4070     53.7       0      1     1.394     a                                      
   0.4390     53.7       0      1     0.984     a                                      
   0.0000     57.9       0      2     0.753     a                                      
   0.0422     57.9       0      2     1.077     a                                      
   0.0919     57.9       0      2     1.444     a                                      
   0.1344     57.9       0      2     1.755     a                                      
   0.1740     57.9       0      2     2.039     a                                      
   0.1923     57.9       0      2     2.172     a                                      
   0.2234     57.9       0      2     2.392     a                                      
   0.2363     57.9       0      2     2.487     a                                      
   0.2437     57.9       0      2     2.544     a                                      
   0.2514     57.9       0      2     2.585     a                                      
   0.2602     57.9       0      2     2.606     a                                      
   0.2763     57.9       0      2     2.609     a                                      
   0.2921     57.9       0      2     2.506     a                                      
   0.3098     57.9       0      2     2.329     a                                      
   0.4039     57.9       0      2     1.280     a                                        

Notes and References

• Key: wtH2O - grams of H2O in the liquid phase; wtH2SO4 - grams of H2SO4 in the liquid phase; solid - 0, H2SO4; BT - Beckmann thermometer temperature (^oC) relative to an arbitrary reference; ref. - source of data.
• Source: a - L. P. Hammett and A. J. Deyrup (1933) J. Amer. Chem. Soc. 55, 2493-2503.