The Thermodynamics Research Center (TRC) specializes in the collection, evaluation and correlation of thermophysical, thermochemical and transport property data for organic compounds.  As a part of the Physical and Chemical Properties Division at National Institute of Standards and Technology, TRC is located in Boulder, Colorado.  TRC is staffed by experienced research scientists and supported by editorial and contractual personnel.

    A goal of TRC is to establish a large, general-purpose archive of experimental data covering  thermodynamic, thermochemical, and transport properties for pure compounds and mixtures of well-defined composition, and to maintain coverage as new data appear.  It is critically important that the data evaluation includes the estimated uncertainties for practically all the numerical data stored.  This feature allows, in principle, determination of the quality of recommended data based upon the original experimental data collected at TRC.

    There are four major types of information stored in this archive - an in-house database.

(1). Compound Identification - Registry numbers identify pure compounds and components of mixtures throughout the archive. Registry numbers link to an empirical formula, a coded representation of the structural formula, and to one or more names. The database contains 113,000 registry numbers and 218,000 names. Reacting systems of one or more compounds also receive registry numbers. Among the stored compounds, approximately 15,800 pure compounds, 9,000 binary and ternary mixtures, and some 2,500 reaction systems have data records. Chemical reactions have a classification code and registry numbers of four species in the reaction.

(2). Sample Descriptions - The database describes over 17,900 distinct samples used in property measurements. The description includes: source of sample, method of purification, and final purity as reported by the authors of the document. Formal abbreviations exist, and by sample numbers identify different samples of the same compound used for measurements in the same document.

(3). Literature References- The database contains citations of original documents and associated information (such as titles, document types, classification of information, and comments) and links to data values. Names of authors appear in a dedicated table linked to the citations. Thus, it is possible to retrieve literature references by year of publication, author, compound identity, property, or combinations of them. The database contains 82,000 citations, of which, over 22,000 citations contribute numerical values to the database.

(4). Numerical Values - Each numerical property value appears in a data record.  A data record also contains values of state variables, and an estimate of the uncertainty of the property. Each data record links to the three kinds of information listed above to codes that identify the property, the primary phase, other phases in equilibrium with the primary phase, other information about the way the data appear in the original document, and a trail of its entry into the database. Property values are converted to SI units on entry while retaining sufficient information to regenerate the original numbers. The database now contains 850,000 data records.