Open Access to the JESS Chemical Reaction Database

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 techniques (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 modelling relies on multicomponent thermodynamic equilibrium modelling, using mass balances for each component and mass action equations to define the relations amongst 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 Unfortunately, some electronic databases of stability constants, such as the NIST [1] and IUPAC [2,3] products, are no longer maintained.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.

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last time modified: September 18, 2024