Chemical Information Sources/Physical Property Searches
The search for chemical and physical property data used to be a hunt through multiple volumes of handbooks, dictionaries and treatises. Increasingly, the major resources are being converted to online versions. Many libraries have access, enabling patrons to utilize these vast collections of evaluated, reliable data with relative ease. However, many of them are very expensive so smaller institutions may not have access. Fortunately, there are now excellent free data collections that are easily available.
Data searching can be divided into a four-step process. The first step is to try to locate the desired properties in these free collections. If that fails, then there are many small data collections commonly available in many libraries in print or as online subscription databases. OPACS or various online guides can be helpful in locating these resources. Next, there are large data collections, in print or online, that are less widely available. And lastly, there is the search of the general literature using a database such as Chemical Abstracts, INSPEC, Compendex or Google.
If you are feeling intimidated by the idea of diving into a property search, there are some excellent web sites to help you get started. One example is ‘’Finding Thermodynamic and Physical Property Data’’ from the University of Texas Libraries. Unlike the lists of resources other libraries offer, some of which are mentioned below, this one is a summary of the process with suggestions and even a tutorial to help you get started.
Step One: General Resources: Freely Available 
National Institute of Standards and Technology Databases
Any discussion of data has to include the National Institute of Standards and Technology, the federal agency charged with developing and applying technology, measurements and standards. In 1963 the National Standard Reference Data System was established, to be coordinated by the National Bureau of Standards (now NIST). The purpose was to provide optimum access to critically evaluated and compiled quantitative physical data. The project was divided into seven areas, including: Nuclear properties, Atomic and molecular properties, Solid State properties, Thermodynamic and transport properties, Chemical kinetics, Colloid and surface properties, and Mechanical properties of materials. The output of the NSRDS consisted of monographs, loose-leaf compliations, and computer tapes. Most of the monographs are available online from NIST. NIST offers a long list of free, web-based databases accessible through the NIST gateway. These databases provide easy access to NIST scientific and technical data covering a broad range of substances and properties including: solubility, kinetic, spectral, and thermodynamic.
Perhaps the best known of these databases is the Chemistry WebBook which provides easy access to chemical and physical property data collected by the Standard Reference Data Program and other contributors. A user can search for chemical species by formula, chemical name, CAS Registry Number, molecular weight, chemical structure, and other concepts such as proton affinity, and reaction. There are 12 options for the type of data to be displayed including Gas and condensed phase thermochemistry data; Phase change data; Reaction thermochemistry data; Gas phase ion energetics data; Ion clustering data; IR, Mass, UV/Vis, Vibrational and electronic spectra data; Constants of diatomic molecules; and Henry’s Law data. Most data is displayed in tabular form with graphical viewing available for some data types. All properties and collection techniques are extensively referenced. A Guide to the NIST Chemistry WebBook by Peter J. Linstrom contains detailed information about search types and data presentation.
Other useful NIST databases include:
- Ceramics WebBook
- NIST Chemical Kinetics Database
- CKMech (Chemical Kinetic Mechanisms)
- CODATA Fundamental Physical Constants
- Hydrocarbon Spectral Database
- High Temperature Superconducting Materials Database
- Ionic Liquids Database (IL Thermo)
- NIST JANAF Thermochemical Tables
- IUPAC-NIST Solubility Database
- NDRL/NIST Solution Kinetics Database on the Web
Free Knovel Databases
Knovel offers a large collection of handbooks, treatises, monographs, and databases integrating technical information with analytical and search tools. Most of these are subscription-based, however, there are some key ones that are available free to academic institutions.
International Critical Tables of Numerical Data, Physics, Chemistry and Technology (1st Electronic Edition)
This classic and well-known reference was originally published from 1926 - 1930 in 7 volumes for the National Research Council. It contains an enormous amount of critical data on inorganic and organic compounds, and pure substances. Featuring physical, thermodynamic, mechanical, and other key properties, it is a major reference source used by those involved in chemistry, physics, and engineering.
In 2003, Knovel undertook the conversion of this publication into full-text searchable electronic format that makes data easily accessible. 7 most important tables were made interactive for increased searchability and user-friendliness.
Interactive tables include:
- Chemical Compounds (Inorganic): B-Table
- Chemical Compounds (Organic): C-Table
- Liquid Crystals Table
- Building Stones Table
- Rotations and Melting Points of Pure Sugars and Sugar Derivatives Table
- Surface Tension Data For Certain Pure Liquids Between 0 and 360°
- Surface Tension Data for All Types of Solutions at All Temperatures Table
- Heats of Solution of Organic Substances Table
- The Electric Conductivity of Pure Non-Metallic Liquids Table
- Viscosity of Pure Liquids Table.
Knovel Critical Tables 2d edition
KCT features tables of physical properties for commonly used chemical compounds. The original edition included 6,000 compounds, expanded to more than 13,000 in the second edition. Each table is fully interactive and searchable by keyword and numeric property value. The thermodynamic tables feature an Equation Plotter that graphically represents the temperature correlation relationships and allows for easy calculation and plotting of the properties. This important, interactive Knovel reference contains tables of physical, solvent, and thermodynamic properties. The physical property tables alone include over 21,000 inorganic and organic compounds, and pure substances. The solvent property tables have data for 385 common solvents, and the thermodynamic property tables have data for over 15,000 compounds. Additionally, several tables make use of the interactive Equation Plotter to plot thermodynamic properties as a function of temperature.
Source of the Data: This information was collected from publicly available Internet sources and from non-copyrighted publications. Knovel's internal scientific staff reviewed the data. If there were differences between values for the same compound and/or the same property, the values were either averaged or a range was created.
Smithsonian Physical Tables 9th Revised Edition
Originally published by the Smithsonian Institution Press in 1954, this classic reference source comprises 901 tables of common physical and chemical data. The information provided is broad in scope. It is of general interest to scientists and engineers, and of particular interest to those involved with physics in its larger sense. In 2003, Knovel undertook the conversion of this publication into full-text searchable electronic format that makes data easily accessible.
MatWeb is a searchable database of properties of more than 86,000 materials. There are several online tools available including Unit of Measure Converter, Weight & Moment of Inertia Calculator, and a Metal and Plastic Hardness Converter. The database is comprised of data and spec sheets supplied by manufacturers and distributors.
There are three kinds of searches: Quantitative, Categorized and Text.
The quantitative search allows you to choose a material category (optional) and then select for up to three properties from a long list in pull-down menus or to choose a alloy category and then up to three material compositions from pull-down menus. To do an advanced search you have to register.
To do a categorized search, you select a material category either from a list or by typing in a text term. You can also search by trade name and manufacturer.
The result of all search is a page giving a variety of information including physical, mechanical, electrical, thermal and processing properties, material notes and a list of vendors. The amount of data available depends on what was supplied by the distributor/manufacturer.
ChemSpider is a free chemical database, sponsored by the Royal Society of Chemistry. It has access to more than 26 million structures and can be searched by name or structure to find properties, spectra, suppliers, and literature references as well as alternate names and SMILES and InChis.
Both experimental and calculated properties are available including standard ones like specific gravity; melting, boiling, and flash points; refractive index and solubility; as well as appearance, stability, toxicity and safety data. Spectra are also available.
ChemIDplus, from the National Library of Medicine, is a free database of 350000 chemical compounds. Records consist of name, synonyms, CAS number, molecular formula, properties, and direct links to biomedical resources. ChemIDplus can be searched by name, molecular weight or property range, and structure.
Step Two: General Resources: Subscription 
There are many smaller handbooks and databases that are familiar and widely available, though not free, should the free resources not provide the needed information. Many have print equivalents.
The old standby CRC Handbook is still available in print, but now also as a CDROM and on the web. In addition to the familiar table of contents or index, the online version can be searched using a basic keyword search or the Structure/Property search. Data can be displayed as static pdfs or in interactive tables which can be sorted, printed and/or exported. Search help is easily accessed from the table of contents window. The online version contains tables from only the most current edition although there are links to discontinued tables from earlier editions.
The Chapman & Hall company originally published a series of printed and CD-ROM products with titles that begin ‘’Dictionary of ...’’ The works are really data compilations or larger handbooks. The information includes descriptive and numerical data on chemical, physical and biological properties compounds; systematic and common names of compounds; literature references; structure diagrams and their associated connection tables. Particularly significant features of the ‘’Dictionary of Organic Compounds’’ are the structural depictions of the substances and properties of derivatives, as well as references to the original literature for synthesis, spectra, etc. of the compound. These are now available online from the CRC CHEMnetBase. All of the dictionaries are available in a single database, the Combined Chemical Dictionary, which covers:
- Dictionary of Analytical Reagents (14,000 compounds)
- Dictionary of Carbohydrates (24,000 compounds)
- Dictionary of Drugs (50,000 compounds)
- Dictionary of Inorganic and Organometallic Compounds (106,000 compounds)
- Dictionary of Natural Products (226,000 compounds)
- Dictionary of Organic Compounds (292,000 compounds)
In general, CCD contains the following compounds: The basic fundamental organic and inorganic compounds of simple structure, including the elements, inorganic binary and ternary compounds (hydrides, halides, oxides, sulfides); virtually every known natural product including those of unknown structure; all currently marketed drugs, including all those listed in generic name compilations; compounds with an established use such as catalysts, solvents, starting materials, synthetic reagents, analytical reagents; important coordination compounds, e.g. amines, phosphines, alkoxy complexes, and major well-characterized bioinorganics; organometallic compounds representative of all important structural types (in the case of ligands with organic substituents, typically the parent member of each series, where known, together with a selection of homologues); important biochemicals and minerals; and other compounds of particular interest because of their chemical, structural or biological properties, including many newly synthesized compounds of active research interest.
Other databases included in CHEMnetBASE are:
- Properties of Organic Compounds, an online version of Handbook of Properties of Organic Compounds, a database covering over 27,000 organic compounds that is searchable by structure. In addition to the print version, there is also a CD version.
- Polymers: a Property Database which provides scientific and commercial information on over 900 polymers. Includes material class and polymer type information as well as a large variety of properties such as volumetric and calorimetric, surface and solubility, transport, mechanical, electrical, optical and stability.
The print Merck Index, now the 14th edition, is still available in many libraries and labs. Online versions are available from database vendors like Dialog, aggregators like Knovel, and other companies like CambridgeSoft. Although the focus of Merck is pharmaceutical in nature, other compounds are covered including:
- human and veterinary drugs
- biotech drugs and monoclonal antibodies
- substances used for medical imaging
- biologicals and natural products
- plants and herbal medicines
- agricultural chemicals (including pesticides and herbicides)
- organic and inorganic chemicals used in commerce and research
- laboratory reagents and catalysts
- dyes, colors and indicators
- environmentally significant substances
The online versions can be searched by name, CAS Registry Number, Molecular formula and weight and well as by other features.The Knovel and Cambridgesoft versions are also searchable by structure.
Knovel is a web-based application integrating technical information with analytical and search tools. Knovel’s three key elements – validated content, optimized search, and data analysis tools – enable researchers to not only easily find relevant data, but also analyze, document and incorporate it into their everyday work. The resource is a searchable database of more than 2500 handbooks and reference sources in science and engineering in 26 subject areas. Although engineering is a major focus of Knovel, also included are: Biochemistry, Biology, and Biotechnology; Chemistry and Chemical Engineering; Food Science; Nanotechnology; Pharmaceuticals, Cosmetics, and Toiletries; and Textiles. Resources are drawn from 45 publishing partners and leading societies. . Knovel's unique approach offers many advantages, including these features:
- Comprehensiveness - 1200 reference titles, 45 publishing partners and relationships with the leading societies
- Unique search capabilities - quick access to relevant and reliable technical content
- Interactive tools - interactive graphs, tables and equations offer your unique teaching and learning opportunities
Perry's Chemical Engineers Handbook was one of many tools available from Knovel. It covers thousands of facts, figures, formulas, tables, graphs, and calculations for chemistry and physics. Exact values or ranges of values of physical properties can be used as search keys, in addition to names of substances or physical properties. Also found on Knovel were the Lange's Handbook of Chemistry and the Chemical Properties Handbook. Unfortunately, in 2011, the publisher of these 3 important works, ended its partnership with Knovel and academic customers. Over 170 McGraw Hill handbooks were withdrawn from Knovel and access was transferred to Access Engineering, McGraw-Hill’s own platform.
Nevertheless, Knovel continues to offer many invaluable data sources including:
- DIPPR Project 801 from the Design Institute of Physical Property
- Polymer Handbook
- Polymer Data Handbook
- several volumes from the massive Landolt-Bornstein tables
- Merck Index
Subscribers can choose all title, a selection of the subject areas, or individual titles so not all subscribing institutions will have access to all the same resources.
Print Handbooks and Treatises
In addition to the few print resources mentioned above in conjunction with online versions, there are many other single and multivolume handbooks and treatises. These can be located by a search of a library OPAC by title or by a subject search for the desired property plus a subheading such as Tables or Handbooks. There are also a number of property guides that have been prepared by university libraries. Some representative ones include:
- Arizona State University Index to Physical, Chemical, and Other Property Data
- University at Buffalo Materials Properties Locator Database
- University of Texas Thermodex
- Vanderbilt University Finding Chemical & Physical Properties
Step Three: Large Data Collections 
There are three major reference collection of historical importance that are still around in libraries today as well as in online versions. All three are German in origin, which has made the print versions often difficult and frustrating to use, though all three are full of a vast amount of reliable data. The online versions are very expensive and may not be easily available.
Landolt-Börnstein (L-B for short) is the largest printed compilation of numerical data in existence today, with over 400 volumes. It covers many areas of interest to chemists, but the fact that the earlier volumes were in German has limited its use in the US. There are now English-language subject and chemical substance indexes that assist in locating tables of interest in the many volumes of the set. Despite the appearance of a CD-ROM version of the indexes starting in 1996 (including an Index of Organic Compounds), the printed L-B is still a difficult set to use.
Data in Landolt-Börnstein covers:
- Elementary Particles, Nuclei and Atoms
- Molecules and Radicals
- Condensed Matter
- Physical Chemistry
- Astronomy and Astrophysics
There is now a database version of L-B, called ‘’Springer Materials’’. In addition to the L-B tables, this resource also includes the Dortmund Data Bank Software & Separation Technology, Database on Thermophysical Properties and the Linus Pauling Files, Database on Inorganic Solid PhaseS, and chemical safety data. The L-B Substance/Property Index can be searched for free on the web by exact name or part of a name, CAS-number, molecular formula or the range of molecular weight (e.g., 50-150), and other options.
Beilstein Handbook of Organic Chemistry and Related Databases If you are looking for a physical property of an organic substance or a two-dimensional depiction of it, the printed Beilstein Handbook of Organic Chemistry or the Reaxys database that incorporates Beilstein is an excellent place to look. This large resource has been the most significant data collection in organic chemistry. Beilstein covers the beginning of organic chemistry in the late 18th/early 19th centuries to the present. The emergence of electronic versions of Beilstein has brought this valuable data to a much broader audience. Although the coverage of the print volumes got considerably behind the present date, the currency of the database is quite good, within a year of the current literature. The printed version is no longer published. With the advent of the far more user-friendly electronic versions, many institutions have retired the print volumes to storage. However, the print set can still be found. A useful guide for using print is available from the University of Buffalo libraries: At the end of 2010, the name Beilstein was retired and the resource is now exclusively issued as Reaxys by a number of different vendors. There are dozens of physical properties reported in Reaxys, and all values are experimental as reported in the original publication. Today there are more than 300 million scientifically measured pieces of data available in the database. The capability to search for substances having certain properties or a range of numerical values of properties is inherent in the Reaxys database, so it is of particular use in searching for organic materials with a given set of properties. Think of how valuable this might be when combined with the capability to conduct exact structure or substructure searches across the millions of compounds in the database.
Distributed among more than 320,000,000 experimental facts about the compounds are the following types of information in Reaxys:
- Molecular and structural formula
- Physical properties
- Chemical reactions
- Chemical behavior
- Spectral information
- Addition compounds and salts
- Transformation products of unknown structure.
- Pharmacological data
- Bioactivity data
- Quantum chemical data
The Gmelin Database and the Gmelin Handbook of Inorganic and Organometallic Chemistry
Beilstein did not routinely cover organometallic compounds. Those are the purview of its sister publication, the ‘’Gmelin Handbook of Inorganic and Organometallic Chemistry’’. With the same degree of comprehensiveness as Beilstein, Gmelin supplies the largest single source of information and data on inorganic and organometallic compounds. The arrangement of Gmelin is by element. Information includes:
- discussions of the element itself
- its binary compounds with substances numbered lower in the Gmelin system numbers
- compounds consisting of more than two elements.
For a given substance, Gmelin provides information on the occurrence, methods of preparation, physical properties, and chemical properties.
Gmelin is available with Beilstein on the Web as ‘’Reaxys’’. Specific compound information from the published volumes of the Gmelin Handbuch through 1975 is indexed in ‘’Reaxys’’. Major sections of prose (e.g. histories of the elements), and graphical information (e.g., phase diagrams, x-ray structures), while often referenced, are not part of the Reaxys data structure. Thus, with Gmelin, it is essential to regularly use the print volumes along with the online database.
Beginning in 1976, Gmelin began indexing the 120 (currently about 60) most important journals in inorganic and organometallic chemistry. Just as Beilstein has a wealth of data on organic substances, the Gmelin database contains much useful data on inorganic and organometallic substances.
Step Four: The Open Literature 
It would seem that journal articles would be excellent sources of physical property data, and for standard data that are routinely reported, they are. The problem is that indexing of physical property data contained in journal articles is not always consistently done by the abstracting and indexing services. There are some journals that are specifically designed to publish data. Two of those are the Journal of Physical and Chemical Reference Data(1972-) and the Journal of Chemical and Engineering Data (1956-). These journals can be searched via the publishers’ web sites or using one of the indexes mentioned below.
One technique to locate data in journal articles is to perform a search that includes terms in the abstracts of the articles in a bibliographic database such as the Chemical Abstracts CA File on STN or SciFinder, INSPEC or Compendex.
In addition to providing access to the data in journal articles, online CA has recently been enriched by the addition of experimental data, collected either by Chemical Abstracts Service or other organizations for most chemical substances, as well as many calculated properties derived using programs from ACD. Not only does the Registry File include the usual physical properties that one might expect to find in a large handbook, but also many properties of interest to those in the pharmaceutical industry or to bioscientists in general. Examples include bioconcentration factor, number of freely rotatable bonds, number of hydrogen bond donor or acceptor sites on the molecule, LogP, etc.
Using Scifinder, one popular interface to CA, a search can be done in any of the three modes, Research Topic, Substance, or Reaction, using chemical name, molecular folmula, CAS Registry Number, or structure. STN and other vendor versions of Chemical Abstracts can be searched according to their protocols. Articles retrieved will contain links to records for all the substances mentioned in the articles. A display of the full substance record will give a complete list of all the experimental and calculated properties.
INSPEC and Compendex can also be useful databases for finding properties. Both contain primarily articles in the physical, engineering, and applied sciences. These can be rich in data. Special search features make it easier to locate such information. For example, INSPEC has classification codes and numerical data indexing that can help a user focus in on properties and even property ranges.
Another technique is to search the full text files of the electronic versions of the journals themselves. Most publishers have their own search engines which can be useful, although by using them you limit yourself to the output of a particular publisher. As more and more scientific journals become available in electronic format, this should prove to be an increasingly important approach, especially as programmers, researchers, and vendors find more innovative ways to search across journal titles. Once you find articles of interest, many publishers provide links to other articles references in those papers regardless of where they were published. The practice of putting supporting information, usually data and experimental procedures, in microform has made this information difficult to locate as it has not always been indexed. This supplementary information is now being put online along with the articles. ACS is an example of a publisher who is now making supplementary information available at their website along with the fulltext of the associated articles.
Google and Google Scholar
In addition to journal articles on the web, there is a lot of producer and distributor information available. Although a Google search can return a lot of irrelevant and/or unreliable information, it is also possible to get good data from catalogs or Material Safety Data Sheets from suppliers such as Sigma-Aldrich. A detailed discussion of a selection of these resources can be found in an article by Ben Wagner. A. Ben Wagner BA, MLIS (2001): Finding Physical Properties of Chemicals, Science & Technology Libraries, 21:3-4, 27-45. There is a revised version that brings the list of sites up to date.
Keep in mind that you are likely to find different values for physical properties when different sources are consulted. In general, the data from the large organizations that are devoted to data production and analysis (e.g., the US National Institute for Standards and Technology and information analysis centers) have more reliable, critically evaluated data. Whenever possible, seek the largest, most authoritative sources of data, checking the original journal articles when there is suspicion of a transcription error.