Dicarboxylic acids are important water-soluble components of atmospheric aerosols. The thermodynamic models of Clegg and Seinfeld (1,2) are based upon available data for aqueous solutions of the acids, their mixtures, their sodium and ammonium salts, and mixtures with inorganic salts. These data are made available on this site, together with brief comments and citations of the original sources.
There is also an interactive calculator for water activities, osmotic coefficents and activity coefficients of pure aqueous acid solutions at 298.15 K, valid to high supersaturation with respect to the acids. The calculator duplicates the results in section 3 of Clegg and Seinfeld (1), which treats the acids H2X as non-dissociating, but also presents values based on the inclusion of both dissociation equilibria H2X(aq) = H+(aq) + HX−(aq), and HX−(aq) = H+(aq) + X2−(aq). The latter calculation yields more accurate results for dilute solutions.
The data have been compiled with support from ACCENT, the European Network of Excellence for Atmospheric Composition Change (an EC 6th Framework Programme), which is gratefully acknowledged.
There are summary pages for each acid, see below, which link to data tables for solutions of the pure aqueous acid, and its mixtures with other compounds. Thus, for example, for malonic acid there are nine sets of tables: one for the pure aqueous acid, and eight for its mixtures with salts, and for malonate and hydrogen malonate salts.
Compositions of the aqueous solutions are specified in a variety of units in the original publications describing the experiments. Here compositions are given, in most instances, in both the original units and in mol per kg of water (molality). More digits have generally been retained in the tabulated data values than are significant, where these have been converted from the original units or are thermodynamic quantities calculated from the published measurement. This avoids rounding errors, and ensures that the original data values can be recovered if needed. However, it also means that the number of digits should not be taken as an indication of the accuracy or precision of the measurement.
Different types of measurement, though yielding the same fitted quantity, can differ greatly in their accuracy and precision. For example, both isopiestic measurements and electrodynamic balance experiments can be used to obtain osmotic coefficients of solutions, but the former experiment is more accurate by a very large margin. Care should therefore be taken when using the information presented in these pages, and the original publications, and those of Clegg and Seinfeld (1,2) should be consulted for discussions of the data.
For some acids we compiled data that were not used in the models, including measurements at temperatures other than 298.15 K. Some of these additional data are also presented here.
Follow this link to calculate water activities, and osmotic and activity coefficients of pure aqueous solutions of the acids at 298.15 K.
The dicarboxylic acids for which data have been collected are listed below. Click on the names to go to the data pages.
| Acid or System | Formula | Acid or System | Formula | |||
| Oxalic | (HOOC)(COOH) | Malic | (HOOC)CH2CHOH(COOH) | |||
| Malonic | (HOOC)CH2(COOH) | Maleic | (HOOC)(CH)2(COOH) | |||
| Succinic | (HOOC)(CH2)2(COOH) | Methylsuccinic | (HOOC)(CH2)2CH3(COOH) | |||
| Glutaric | (HOOC)(CH2)3(COOH) | Acid mixtures | (various) |
(1) S. L. Clegg and J. H. Seinfeld (2006a) Thermodynamic models of aqueous solutions containing inorganic electrolytes and dicarboxylic acids at 298.15 K. I. The acids as non-dissociating components. J. Phys. Chem. A, 110, 5692-5717.
(2) S. L. Clegg and J. H. Seinfeld (2006b) Thermodynamic models of aqueous solutions containing inorganic electrolytes and dicarboxylic acids at 298.15 K. II. systems including dissociation equilibria. J. Phys. Chem. A, 110, 5718-5734.