The new electronic database of the Thermochemical Database Project (TDB)

    The new interactive TDB electronic database is now available. Registration with the NEA is required in order to obtain access. If you are already registered, please contact us at to grant you access.

    Login to the TDB e-database Register to obtain access

    The content of the e-TDB includes:

    • all published selected thermodynamic data of the 13 Chemical Thermodynamic Series volumes. The data are searchable by element, species and type of data, among others;
    • a Phreeqc formatted database file, ready to download and use;
    • information on all the bibliographic references that have been used in the TDB published material. The bibliography is searchable by title, journal, year and author among others.

    With the current version, SIT data will not be searchable through the software interface, but a pdf file of all currently selected Specific Ion Interaction Theory parameters (SIT) that should be used in conjunction with the selected data for aqueous species for calculations at non-zero ionic strength is made available. The list is taken from the latest NEA TDB publication (Volume 13 - Iron Part 1).

    Phreeqc database

    One of the main features of the new TDB tool is that the database is made available in a Phreeqc format that can be downloaded below.

    Phreeqc database

    For Phreeqc purposes, several selected reactions from the TDB publications had to be re-written in terms of SOLUTION MASTER SPECIES. Accordingly, the respective solubility constants were recalculated (when the required information was available), for this purpose. When not enough information was available to recalculate the re-written reactions, these were not included in the Phreeqc file.

    Conforming vs non-conforming reactions

    On the Search tool of the new electronic database, only selected reactions published at the TDB books are displayed. They are characterised as Conforming or Non-Conforming, reflecting their status with regard to Phreeqc standards (Conforming if they are written in terms of SOLUTION MASTER SPECIES and Non-Conforming if they are not).


    The addition of any other aqueous species to this internally consistent database can result in a modified data set which is no longer rigorous and can lead to erroneous calculation results. The situation is similar, to a lesser degree, for the addition of gases and solids.

    It should also be noted that the data set presented here are not "complete" for all conceivable systems and conditions. Gaps due to lack of reliable experimental information are pointed out in the published review reports. The TDB selected data sets are based only on experimental data and do not contain estimations where no reliable data is available.

    The reaction data do not contain all conceivable reactions for a certain element, only those for which primary data selections have been made in the reviews. These selected reaction data have been used, together with the selected auxiliary data, also available in the database, to derive the corresponding formation data. As these auxiliary data are used in the evaluation of the selected data for the reviewed elements, it is essential to always use them in conjunction with the selected formation data. The use of other auxiliary data can lead to inconsistencies and erroneous results.

    More information about the procedures used for selecting and extrapolating data is available in the TDB guidelines.

    The NEA TDB project makes extensive use of a formulation of the Specific Ion Interaction Theory (SIT) for the extrapolation of experimental equilibrium data to zero ionic strength. In order to avoid inconsistencies in the results of speciation calculations, the NEA selected data should be used in conjunction with this SIT formulation and the selected ion interaction coefficients when doing calculations at non-zero ionic strengths. The TDB-2 Guideline contains further details on the use of ionic strength correction procedures.

    Please note that although the selected data are directly made available here, the data should always be used taking into account the information in the published review reports. The "blind" use of selected data without the information in the published reviews is not recommended.


    NEW The TDB-Iron Part 2 selected data have now been released in the electronic database. Please note that the full publication is expected to be released in the coming months.

    The SIT tables have also been updated. However, the newly released reaction data have not yet been included in the Phreeqc file.

    Reactions for the following species, even though selected and available in 2019LEM/PAL, are not currently included in the electronic database due to design limitations that we are working to solve: Fe2+, K4Fe(CN)6(cr), SeO42-, H2PO4-, CN- and SiOH4(aq).


    We will be happy to hear from you, should you have comments and feedback on the new TDB electronic database, and if you encounter errors that need to be corrected. E-mail contact: .