What kinds of data does the NIST Chemistry WebBook contain?
The NIST Chemistry WebBook (SRD 69) is a free-access compilation of chemical and physical data distributed by NIST under its Standard Reference Data Program. It covers four broad categories: thermochemical data, spectra, ion energetics, and thermophysical properties of fluids. Use it when you need a reference value for a specific compound or reaction — for example, a heat of formation, an IR spectrum, or the viscosity of a fluid at a given temperature. It is a lookup resource, not a computational tool, and NIST states it reserves the right to charge for access in the future.
Thermochemical data
Thermochemical data is available for over 7,000 organic and small inorganic compounds, and reaction thermochemistry for over 8,000 reactions.
Per-compound values include:
- Enthalpy of formation
- Enthalpy of combustion
- Heat capacity
- Entropy
- Phase transition enthalpies and temperatures
- Vapor pressure
Per-reaction values include:
- Enthalpy of reaction
- Free energy of reaction
Spectra
Spectral data covers several techniques, with the number of compounds varying by type:
| Data type | Compounds covered |
|---|---|
| Mass spectra | Over 33,000 |
| IR spectra | Over 16,000 |
| Gas chromatography data | Over 27,000 |
| Electronic and vibrational spectra | Over 5,000 |
| UV/Vis spectra | Over 1,600 |
Ion energetics
Ion energetics data is provided for over 16,000 compounds, including:
- Ionization energy
- Appearance energy
- Electron affinity
- Proton affinity
- Gas basicity
- Cluster ion binding energies
Thermophysical properties of fluids
Thermophysical property data covers 74 fluids. The properties listed are:
- Density and specific volume
- Heat capacity at constant pressure (C p)
- Heat capacity at constant volume (C v)
- Enthalpy and internal energy
- Entropy
- Viscosity and thermal conductivity
- Joule-Thomson coefficient
- Surface tension (saturation curve only)
- Sound speed
Other data
The WebBook also includes constants of diatomic molecules (spectroscopic data) for over 600 compounds.
How to find a specific value
You can search for data on a specific compound by:
- Name
- Chemical formula
- CAS registry number
- Molecular weight
- Chemical structure
- Selected ion energetics and spectral properties
What to keep in mind
NIST states that it uses its best efforts to deliver a high-quality copy of the database and to verify that the data were selected on the basis of sound scientific judgment, but it makes no warranties to that effect and is not liable for damage resulting from errors or omissions. Treat the values as reference data to check against your own measurements or other sources rather than as a guaranteed authority for critical decisions.