Maleic Acid Mixture Data

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

(1a) Relative Humidity of Deliquescence of Mixtures with (NH4)2SO4

  DRH     xH2Maleic  Solid      t       uncert.(a)   uncert.(b)    ref.     weight
  0.82     0.0        1         24        0.03         0.05         a          -
  0.78     0.12       1         24        0.03         0.05         a          -
  0.715    0.53       1,2       24        0.03         0.05         a          -
  0.84     0.87       2         24        0.03         0.05         a          -
  0.87     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; xH2Maleic - the mole fraction of the acid in the solute, equal to nH2Maleic/(nH2Maleic + n(NH4)2SO4); t - experimental temperature (^o); uncert.(a) - uncertainty in the DRH; uncert.(b) - uncertainty in xH2Maleic; 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 with (NH4)2SO4, of Eutonic Composition

   nS/nW      1/aW         aW     mH2Maleic  m(NH4)2SO4     t    uncert.   ref.   weight  
  0.249894   1.44342     0.6928    7.6288     6.2425      25.0   0.009      a       -                                            
  0.249894   1.43058     0.6990    7.6288     6.2425      25.0   0.009      a       -                                            
  0.250073   1.45182     0.6888    7.6343     6.2470      25.0   0.009      a       -                                            
  0.250073   1.47276     0.6790    7.6343     6.2470      25.0   0.009      a       -       
  0.250073   1.45818     0.6858    7.6343     6.2470      25.0   0.009      a       -       
  0.154269   1.26214     0.7923    4.7095     3.8537      25.0   0.009      a       -       
  0.114045   1.17311     0.8524    3.4816     2.8489      25.0   0.009      a       -       
  0.057775   1.09226     0.9155    1.7638     1.4433      25.0   0.009      a       -       
  0.019560   1.03170     0.9693    0.5971     0.4886      25.0   0.009      a       -       
  0.010400   1.00326     0.9968    0.3175     0.2598      25.0   0.009      a       -       
  0.014861   1.02306     0.9775    0.4537     0.3712      25.0   0.009      a       -       
  0.031582   1.04764     0.9545    0.9641     0.7889      25.0   0.009      a       -       
  0.008095   1.01565     0.9846    0.2471     0.2022      25.0   0.009      a       -       
  0.015010   1.02593     0.9747    0.4582     0.3750      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 nH2Maleic/(nH2Maleic + n(NH4)2SO4) = 0.550. The uncertainty in this figure is approximately ±0.01. The solutions at the lowest water activity (about 0.69) are simultaneously saturated with respect to both solutes.