ThermoML - An XML-based IUPAC Standard for Thermodynamic Property Data

"ThermoML" is reserved namespace for the XML-based IUPAC standard for experimental and critically-evaluated thermodynamic property data storage and capture which was developed under the IUPAC project 2002-055-3-024 (M. Frenkel, Task Group Chairman, J. H. Dymond, E. Koenigsberger, K. N. Marsh, S. E. Stein, W. A. Wakeham- members).

This project is conducted as one of the activities of the IUPAC Committee on Printed and Electronic Publications (CPEP)

ThermoML covers essentially all experimentally determined thermodynamic and transport property data (more than 120 properties) for pure compounds, multicomponent mixtures, and chemical reactions (including change-of-state and equilibrium). Although the focus of ThermoML is properties determined by direct experimental measurement, ThermoML does cover key derived property data such as azeotropic properties, Henry's Law constants, virial coefficients (for pure compounds and mixtures), activities and activity coefficients, fugacities and fugacity coefficients, and standard properties derived from high-precision adiabatic heat-capacity calorimetry.

The ThermoML structure represents a balanced combination of hierarchical and relational elements. The ThermoML schema structure explicitly incorporates structural elements related to basic principles of phenomenological thermodynamics: thermochemical and thermophysical (equilibrium and transport) properties, state variables, system constraints, phases, and units. Meta- and numerical-data records are grouped into 'nested blocks' of information corresponding to data sets. The metadata records precede numerical data information, providing a robust foundation for generating 'header' records for any relational database where ThermoML-formatted files could be incorporated. The structural features of the ThermoML metadata records ensure unambiguous interpretation of numerical data as well as data-quality control based on the Gibbs Phase Rule.

ThermoML — an XML-based IUPAC Standard for storage and exchange of experimental thermophysical and thermochemical property data — was fully described (Pure Appl. Chem., 2006, 78, 541-612). Supporting information for this article includes several examples illustrating the use of ThermoML to process experimental data for pure compounds, mixtures, and chemical reactions as well as the initial ThermoML specification.

The framework of the ThermoML has previously been described in details in the article "ThermoML - an XML-based Approach for Storage and Exchange of Experimental and Critically Evaluated Thermophysical and Thermochemical Property Data. 1. Experimental Data" by M. Frenkel, R. D. Chirico, V. V. Diky, Q. Dong, S. Frenkel, P. R. Franchois, D. L. Embry, T. L. Teague, K. N. Marsh, and R. C. Wilhoit, published in the Journal of Chemical and Engineering Data 2003, 48, 2-13. Extensions to the ThermoML schema for the expression of uncertainties were described (J. Chem. Eng. Data, 2003, 48, 1344-1359 & Supporting information), as were extensions for representation of critically evaluated data, predicted data, and Equation Representation (J. Chem. Eng. Data, 2004, 49, 381-393 & Supporting information). Supporting Information documents for these articles include examples illustrating application of the new extensions. As ThermoML evolves, this site maintains the current ThermoML specifications [ThermoML.xsd].

Currently, ThermoML is extensively used in the new data delivery process involving major journals in the field such as Journal of Chemical and Engineering Data (see, Editorial, 2003, 48, 1) and Journal of Chemical Thermodynamics (see, the Journal 2004 Editorial, 2004, 36, iv), computer application development companies, and Thermodynamics Research Center (TRC) at the National Institute of Standards and Technology. In order to simplify the process of the data compilation by the users, the Guided Data Capture software (GDC) has been developed (J. Chem. Inf. Comp. Sci., 2003, 43, 15-43). The current ThermoML schema and a variety of the ThermoML files containing experimental thermodynamic data reported in the publications of the above-mentioned journals could be downloaded from the TRC Web site (trc.nist.gov).