ThermoML is an XML-based approach for storage and exchange of experimental and critically evaluated thermophysical and thermochemical property data. Extensions to the ThermoML schema for the expression of uncertainties are described. Basic principles, scope, and description of all new structural elements are discussed. Representation of upper and lower limits for property values is also addressed. 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). Properties of polymers and radicals and some properties of ionic systems are not represented at present. The present role of ThermoML in global data submission and dissemination is discussed with particular emphasis on cooperation between major journals in the field and the Thermodynamics Research Center (TRC) at the National Institute of Standards and Technology. The text of several data files illustrating the expression of uncertainties in ThermoML format for pure compounds, mixtures, and chemical reactions are provided as Supporting Information, as well as the complete updated ThermoML schema text.

ThermoML is an XML-based approach for storage and exchange of experimental and critically evaluated thermophysical and thermochemical property data. The basic principles, scope, and description of all structural elements of ThermoML are discussed. 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). The primary focus at present is molecular compounds. 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 highprecision adiabatic heat-capacity calorimetry. The role of ThermoML in global data submission and dissemination is discussed with particular emphasis on the new cooperation in data processing between the Journal of Chemical and Engineering Data and the Thermodynamics Research Center (TRC) at the National Institute of Standards and Technology. The text of several data files illustrating the ThermoML format for pure compounds, mixtures, and chemical reactions, as well as the complete ThermoML schema text, is provided as Supporting Information. Some important issues related to characterization of thermodynamic data are beyond the scope of this paper (uncertainty specification) or are considered in generic terms only (critically evaluated data). These issues will be considered in subsequent papers in this series.

The ideal gas thermodynamic properties of forty-four key organic oxygen compounds in the carbon range C 1 to C 4 have been calculated by a statistical mechanical technique. The properties determined are the heat capacity (C;), entropy {S' (T)-S' (O)}, enthalpy {Jr (T)-Jr (O)}, and Gibbs energy function {Go (T)-Jr (O)} IT. The calculations have been performed, in most cases, over the temperature range 0 to 1500 K and at 1 bar. The contributions to the thermodynamic properties of compounds having internal-or pseudo-rotations have been computed by employing a partition function formed by the summation of the internal rotational or pseudorotational energy level for each rotor in the given molecule. These energy levels have been calculated by solving the wave equation using appropriate barrier heights, rotational constants, and potential functions for the given rotations. The thermodynamic properties have been calculated using a rigid-rotor. and harmonic-oscillator molecular model for each species. The sources of molecular data and the selection of the values used in the calculation are described. The calculated C; and {S' (T)-SO (O)} values are compared with experimental results where appropriate.

The thermodynamic properties (Cpo, So, Ho−H0o, (Ho−H0o)/T,−(Go−H0o)/T, ΔHfo, ΔGfo and log Kf) for ethane and propane in the ideal gaseous state in the temperature range from 0 to 1500 K and at 1 atm were calculated by statistical thermodynamic methods based on a rigid-rotor harmonic-oscillator model. The internal rotation contributions to thermodynamic functions were evaluated by using a partition function formed by summation of internal rotation energy levels. The calculated heat capacities and entropies compare favorably with available experimental data.

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