The following are freely available websites with useful collections of chemical data.
- NIST Reference on Constants, Units and Uncertainty
This National Institute of Standards and Technology has a searchable and browsable list of the important physical constants with bibliography, as well as a thorough description of the SI system of units and a description of methods of expressing degree of uncertainty in measurements. An excellent reference site.
- The Laws List
This collection of laws, rules and constants in physics, compiled by Erik Max Francis, includes a number of interest in physical chemistry, e.g. the gas laws, Rydberg formula, etc.
WebElements is a hypertext-linked collection of property data on the first 112 elements (and growing...) including (where available): general, chemical, physical, nuclear, electronic, biological, geological, crystallographic, reduction potential, isotopic abundances, electronic configurations, ionization enthalpy data and additional textual information, especially on the history of the elements.
- Table Of The Nuclides
The Table of the Nuclides (created by the Korea Atomic Energy Research Institute) first presents a map of all known nuclides. Each horizontal row represents one element; colored dots indicate the known isotopes of that element. A vertical column represents the nuclides with same neutron numbers. By clicking on a region of the chart, you may see a more detailed chart section. From the colors on the chart, you can get an idea of the life time of a nuclide. By clicking on a cell, you can get properties of the nuclide or atom. For additional nuclear data, see the National Nuclear Data Center site.
- NMR Periodic Table of the Elements
This is a compilation of magnetic resonance data on the elements in periodic table form, compiled by the NMR facility at Texas A&M University. See also the Magnetic Resonance Periodic Table of the University of Illinois Biomedical Magnetic Resonance Laboratory.
- NIST Online Physical Data
This site contains links to the NIST collections of physical data which have so far been made available over the web, plus a catalog of other NIST data collections.
- NIST Chemistry Webbook
The NIST WebBook will provide access to the full array of data compiled and distributed by NIST under the Standard Reference Data Program. The current edition, the Chemistry WebBook, contains, among other data:
(1) Thermodynamic data on an extensive set of organic and small inorganic compounds - Enthalpy of formation, Heat capacity and Entropy for over 6000 compounds.
(2) A large set of ion-energetics data - Ionization potential and Appearance potential for over 16,000 compounds.
(3) IR spectra, mass spectra and electronic/vibrational spectra data for thousands of compounds.
(4) Reaction thermochemistry data for over 9000 reactions.
(5) Constants of diatomic molecules (spectroscopic data) for over 600 compounds.
(6) Thermophysical property data for 33 fluids
Data on specific compounds may be located by name, formula or CAS Registry Number.
- Techniques for Organic Reactions, Visualization and Spectroscopy
This set of databases, created by the Computer Chemistry Center at the University of Erlangen, includes the WWW Chemical Structure Database, containing more than 2250 automatically collected chemical structures from the Internet, complete with information about the referring HTML pages. It is searchable by name, CAS Registry Number, molecular formula and other data, as well as by structure (uploaded in SMILES string format). Also available are collections of 3D structure coordinates, GIF and VRML renditions of molecules and more. An excellent site.
- CODATA Key Values for Thermodynamics
The Committee on Data for Science and Technology (CODATA) has conducted a project to establish internationally agreed values for the thermodynamic properties of key chemical substances. This table presents the final results of the project. Use of these recommended, internally consistent values is encouraged in the analysis of thermodynamic measurements, data reduction, and preparation of other thermodynamic tables. The table includes the standard enthalpy of formation at 298.15 K, the entropy at 298.15 K, and the quantity H ° (298.15 K)-H °(0). A value of 0 in the DeltafH ° column for an element indicates the reference state for that element. The standard state pressure is 100000 Pa (1 bar).
- Organic Compounds Database
This database, compiled at Virginia Tech and made available by Colby College, provides physical data on a large number of organic compounds, including molecular weight, melting point, boiling point, index of refraction and UV absorption peaks. It is searchable by name, molecular formula or by data values for the above properties.
SOLV-DB is a database of physical, chemical, health and safety, regulatory and environmental fate data on over 100 common organic solvents, provided by the National Center for Manufacturing Sciences. It is searchable by name, formula, CAS Registry Number, property data values and so forth.
- The Good Scents Co. Information Index
This commercial site includes an information index on a wide variety of compounds used in the perfumery industry. The index is divided into categories, such as "essential oils" and "perfumery raw materials (synthetic)". Within each category, compounds are listed alphabetically (using ASCII alphabetization, so compounds whose names begin with "(+)", "(-)" or numbers gravitate to the top of the lists. Compound records give synonyms, descriptions of aroma and perfumery uses, and CAS RN's, and physical property data (density, mp, bp) where available. Unfortunately, the index is not searchable by name or by property, which would enhance its value tremendously. Still, its information on compound odors is perhaps unique on the Internet. For more scents of chemicals, see the ChemConnections Smells Database and the Flavornet list. as well as an excellent site by Dr. John Leffingwell on Chirality and Odour Perception.
- IUPAC Chemical Nomenclature
This site, created by G.P. Moss of Queen Mary and Westfield College, contains a number of IUPAC documents on organic and biochemical nomenclature, in many cases including sample structure diagrams.
- IUPAC Nomenclature of Organic Chemistry
Another good nomenclature site, easily browsable and searchable, provided by Advanced Chemistry Development (ACD) Inc.
While this web site does not actually list thermophysical or thermochemical data, it is an extremely useful index to such data available in a host of printed data collections (excluding Beilstein, Landolt-Bornstein, the CRC Handbook and Perry's Handbook), searchable by name of property, class of compound, specific compound or combinations of the above. Thermodex is the creation of the Library of the University of Texas at Austin.