NIST Chemistry WebBook

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https://webbook.nist.gov/chemistry/

The NIST Chemistry WebBook is the online reference of NIST Standard Reference Database 69. It provides thermochemical, thermophysical and ion energetics data for over 40,000 chemical species, together with IR, mass and UV/Vis spectra, gas chromatography retention indexes and computed 3D structures.

Search works by name, formula, CAS number, InChI, reaction, author or molecular weight.

The data come from collections maintained by the NIST Standard Reference Data Program and outside contributors, which separates it from crowd-edited chemistry sites.

Tip: a fluid properties module gives high accuracy data for a selected group of fluids, and a group additivity tool estimates gas phase thermodynamic properties from a submitted structure.

Process, materials and combustion engineers use it for enthalpies of formation, heat capacities, boiling points and vapor pressures when sizing or modeling a system. Scientists identify compounds from spectra and retention indexes. A citation guide is provided for each record. NIST states that it reserves the right to charge for access in the future.

Disciplines: Chemistry, Chemical engineering, Thermodynamics, Materials science, Physics.

Free alternative to CRC Handbook, Reaxys, DIPPR.

NIST Chemistry WebBook compared with CRC Handbook, Reaxys and DIPPR
NIST Chemistry WebBook	CRC Handbook	Reaxys	DIPPR
Content and data types: Thermochemical, thermophysical and ion energetics data for over 40,000 species, plus IR, mass and UV/Vis spectra, retention indexes, Henry law constants and 3D structures. Tools include fluid properties and a group additivity estimate for gas phase properties.	Content and data types: Four parts: data on chemical substances, data for the practice of chemistry and physics, data for modern chemical laboratories, and reference tables with units, constants and nomenclature. It is a broad reference for chemistry and physics, not a spectral or reaction database.	Content and data types: Property, spectral and structure-property data, published reactions and synthesis routes, with a synthesis planner and predictive retrosynthesis. It also indexes journals and patents, which the WebBook does not.	Content and data types: 2,330 substances of industrial priority (as of 2016), with 34 thermodynamic constants and 15 temperature-dependent properties and recommended model parameters. It is narrower than the WebBook but built for process design values.
Data evaluation and provenance: Data come from collections of the NIST Standard Reference Data Program and outside contributors. NIST gives no warranty that the data are error-free, and each record has a citation guide with a DOI.	Data evaluation and provenance: The handbook is revised yearly with new data and scientific areas, and reviewed by over 100 subject matter experts.	Data evaluation and provenance: Over 500 million published experimental facts are drawn from the literature, with more than 260 million substances and 73 million reactions indexed.	Data evaluation and provenance: All available data are assessed for accuracy, thermodynamic consistency and reliability within chemical classes. Where no experimental data exist, established prediction methods fill the gap and experts give recommended values.
Access and cost model: Open access today. NIST states that it reserves the right to charge for access in the future.	Access and cost model: Sold as a print hardback, and organizations can also hold an online subscription.	Access and cost model: Subscription-based, with institutional options and usage analytics.	Access and cost model: Requires a yearly leasing fee, with standalone and server licences and prices on request. DIPPR is a technical society of AIChE, and DECHEMA distributes the database in Europe.
Search and delivery format: Search by name, formula, CAS number, InChI, reaction, author or molecular weight, in the browser. The database was last updated in 2025.	Search and delivery format: Available as a printed book and as an online database with tools.	Search and delivery format: Web platform with on- and off-campus access and structure-based search.	Search and delivery format: Used as a standalone MS-Access database, with the DIADEM software, or with the DETHERM database in its native formats.