Malic Acid Mixture Data

The tables of data are given below in the order the systems are listed on the main malic acid page.

(1a) Relative Humidity of Deliquescence of Mixtures of l-Malic Acid with (NH4)2SO4

  DRH     xH2Malic  Solid      t       uncert.(a)   uncert.(b)    ref.     weight
  0.82     0.0       1         24        0.03         0.05         a          -
  0.76     0.245     1         24        0.03         0.05         a          -
  0.70     0.46      1         24        0.03         0.05         a          -
  0.565    0.66      1,2       24        0.03         0.05         a          -
  0.525    0.82      2         24        0.03         0.05         a          -
  0.52     0.83      2         24        0.03         0.05         a          -
  0.59     1.0       2         24        0.03         0.05         a          -

Notes and References

Symbols: DRH - the equilibrium relative humidity (as a fraction, not %) above an aqueous solution saturated with respect to a solid phase; xH2Malic - the mole fraction of l-malic acid in the solute, equal to nH2Malic/(nH2Malic + n(NH4)2SO4); t - experimental temperature (^o); uncert.(a) - uncertainty in the DRH; uncert.(b) - uncertainty in xH2Malic; ref. - source of data; weight - the weight assigned in the fit of the model to determine parameter values.
Source: a - S. D. Brooks, M. E. Wise, M. Cushing and M. A. Tolbert (2002) Geophys. Res. Lett. 29, doi:10.1029/2002GL014733.
These data were extracted from Figure 2 of Brooks et al. The solids were not identified, and are assumed to be the solid acid and salt only.

(1b) Water Activities of Mixtures of l-Malic Acid with (NH4)2SO4, of Eutonic Composition

   nS/nW      1/aW         aW    mH2Maleic  m(NH4)2SO4      t    uncert.   ref.   weight  
  0.613107   1.858250    0.5381   22.3898    11.6429      25.0   0.009      a       -   
  0.613107   1.880650    0.5317   22.3898    11.6429      25.0   0.009      a       -                                                              
  0.613107   1.849740    0.5406   22.3898    11.6429      25.0   0.009      a       -                                                              
  0.038413   1.054420    0.9484    1.4028     0.7295      25.0   0.009      a       -                                                              
  0.248723   1.396440    0.7161    9.0830     4.7233      25.0   0.009      a       -                                                         
  0.149233   1.227840    0.8144    5.4498     2.8339      25.0   0.009      a       -              
  0.116497   1.175510    0.8507    4.2543     2.2123      25.0   0.009      a       -              
  0.044894   1.067870    0.9364    1.6395     0.8525      25.0   0.009      a       -              
  0.013048   1.038810    0.9626    0.4765     0.2478      25.0   0.009      a       -              
  0.011883   1.023410    0.9771    0.4340     0.2257      25.0   0.009      a       -              
  0.018457   1.033490    0.9676    0.6740     0.3505      25.0   0.009      a       -              
  0.006624   1.010380    0.9897    0.2419     0.1258      25.0   0.009      a       -              
  0.059157   1.083320    0.9231    2.1603     1.1234      25.0   0.009      a       -              
  0.008419   1.027080    0.9736    0.3075     0.1599      25.0   0.009      a       -

Notes and References

Symbols: nS/nW - moles of total solutes per mole of water; aW - water activity; prefix m denotes molality; t - experimental temperature (^oC); uncert. - uncertainty in the measured water activity (average of the 0.5% to 1.35% in RH given by Wise et al., 2003); ref. - source of data; weight - the weight assigned in the fit of the model to determine parameter values.
Source: a - M. E. Wise, J. D. Surratt, D. B. Curtis, J. E. Shilling and M. A. Tolbert (2003) J. Geophys. Res. 108, doi:10.1029/2003JD003775, 8 pages.
The original data of Wise et al. (2003), which are not tabulated in their paper, were obtained directly from the authors. The mole fraction of the acid in the eutonic solution is nH2Malic/(nH2Malic + n(NH4)2SO4) = 0.6579. The uncertainty in this figure is approximately ±0.01. The solutions at the lowest water activity (about 0.54) are simultaneously saturated with respect to both solutes.