The Joint Expert Speciation System (JESS) Thermodynamic Database is now available as a set of freely downloadable PDF files.
Chemical speciation refers to the distribution of an element amongst chemical species in a system. Knowledge about the speciation of an element is mandatory for the evaluation of bioavailability, toxicity and environmental fate and transport. Unfortunately, it is generally not possible to determine the complete speciation using analytical chemistry methods alone.
Methods for speciation analysis are complex and often using hyphenated techniquies (see Brief summary: Tools for elemental speciation analysis
). Since environmental concentrations of many elements of interest are low, and not all species can be measured directly, total speciation is often not achievable by speciation analysis. Therefore, total speciation generally relies on utilising analytical methods in conjunction with chemical speciation models.
Speciation modellingThe new JESS initiative:
relies on multicomponent thermodynamic equilbrium modelling using mass balances for each component and mass action equations to define the relations among the different components. The correctness of the modelling depends on the quality of the equilibrium constants used in the model. Uncertainty in the predicted speciation results from decision rule uncertainty, model uncertainty, parameter uncertainty and parameter variability. Unfortunately, some electronic databases of stability constants, such as the NIST  and IUPAC [2,3] products are no longer maintained.
In order to preserve the enormous effort that has been put into compiling the JPD database, the database is now made freely available as a set of PDF files. This reaction database contains about 280,000 thermodynamic parameters (equilibrium constants, enthalpies, etc.) as published in the literature for over 80,000 chemical reactions. For data quality evaluation it includes some quantitative indication of parameter reliability based mainly on intra- and extra-reaction consistency.
For more details of the initiative, please consult the following publication:
Peter M. May, Montserrat Filella
, Open Access to the JESS Chemical Reaction Database
, J. Solution Chem., (2023). DOI: 10.1007/s10953-023-01302-2 Related Publications:
 NIST Critically Selected Stability Constants of Metal Complexes: Version 8.0: (2013). https://www.nist.gov/srd/nist46
 L.D. Pettit, K.J. Powell, The IUPAC Stability Constants Database (SC-Database)
, Release 4.71. Academic Software, U.K. (2005)
 L. Pettit, G. Pettit, A more realistic approach to speciation using the IUPAC Stability Constants Database
. Pure Appl. Chem. 81, 1585–1590 (2009). DOI: 10.1351/PAC-CON-08-08-21
ZENOBO: JESS Thermodynamic database of chemical reactions v8.9 GITHUB: Where to find equilibrium constants? . A Guide
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last time modified: July 21, 2023