Quality of Data
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Electronic resource |
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UT-Austin restricted |
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Print resource |
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Critically evaluated data |
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Recommended |
Most but not all data "handbooks" are secondary sources, meaning they are compilations of data previously reported in the primary literature, mainly journals. The reliability of secondary sources depends on both the quality of the original data and on the care taken in compiling and evaluating them. Most compilations cite original literature references for the data. Follow up on these if necessary. Compilations that don't include such references should be used with caution. The age of the data is also relevant: the enthalpy of a compound is the same today as it was in 1905 - what has changed is the precision of measurement and estimation methods. Still, don't dismiss data just because it's old.
The same caveats apply to data you might find on the Internet: a value found on a college lab course web page or Wikipedia cannot be treated the same as a value contained in a NIST database. Ask these questions for all sources: When was this work done, and by whom? Were the data determined experimentally or derived by calculation (estimated)? What experimental parameters or special conditions applied?
The term "critically evaluated" is a useful one to look for in secondary sources: this means that independent experts have examined the data and procedures, and in cases where different values have been reported, rated them for accuracy. In addition to most data found in Beilstein, Gmelin, and Landolt-Börnstein, data compiled by the following entities are critically evaluated.
- National Institute for Standards and Technology (formerly National Bureau of Standards)
- NIST's National Standard Reference Data Service is a coordinating body for many different data collection centers. Much of the data collected for this body is now published in the Journal of Physical and Chemical Reference Data, but earlier data can be found in the NSRDS book series (see above) and in the NBS Circulars, Technical Notes, Monographs, and Special Publications. NIST also publishes electronic datafiles in its Standard Reference Database series and the NIST WebBook. Data collected and evaluated by NIST can be considered extremely reliable.
- DIPPR
- The Design Institute for Physical Property Research Project 801 is affiliated with AIChE and is now located at Brigham Young University.
- CINDAS
- Founded by Y.S. Touloukian, the Center for Information and Numerical Data Analysis and Synthesis (formerly at Purdue University, now private) has carried out a systematic research program on the properties and behavior of materials since 1960. They offer an interactive web version of Thermophysical Properties of Matter on a subscription basis.
- DECHEMA
- The Society for Chemical Engineering and Biotechnology is based in Frankfurt, Germany. They publish the Chemical Data Series and the DETHERM database.
- IUPAC
- Data published under the auspices of the International Union of Pure and Applied Chemistry are particularly valuable in the areas of solubility, electrochemistry, and thermodynamics. The Solubility Data Series (formerly a book series, now published in JPCRD) is the most extensive critical compilation of solubility data available.
- Thermodynamics Research Center
- Founded in 1942 by Frederick D. Rossini, the TRC was originally established in the NBS to undertake the American Petroleum Institute Research Project 44. For many years the TRC was located at Texas A&M University; in 2000 it moved back to NIST, and is now headquartered in Boulder, Colorado.
Other compilations must be used with appropriate caution. Many of them merely gather data from the literature uncritically and republish them in tabular form. If validity is in doubt, try to verify it in another source or obtain the original source document.
Sometimes the original documents are not easily obtained. It has always been a mystery why scientists would spend so much time, effort, and money to determine property data, only to publish it in obscure journals, in ultra-expensive handbooks that few libraries can afford, in virtually invisible technical reports -- or not publish it at all. While some data are intentionally proprietary, other data are obscure because of geography or politics. For example, a great deal of fundamental data collection was carried out by Soviet scientists during the Cold War era, and unclassified results were published in Russian-language journals. Some of these journals are available in English translations, but many are not. Compilations that cite these foreign sources must sometimes be trusted as the last resort.
If it's possible to contact a researcher directly, that person may be happy to share raw data. Contacting a manufacturer for desired data on a commercial product is a last resort, but this information is often minimal and companies will typically decline to provide it.
