Data methodology

PubCAS connects chemical identity records with source material and useful calculations. Every published substance has a source CAS cross-reference, a passed CAS checksum, a formula and a reported mass.

Identity and selection

The initial 1,000 records are selected from ChEBI release 255, prioritising common laboratory chemicals, elements, inorganic materials and source-rich entries. Only ChEBI three-star entries are used. ChEBI cross-references are evidence from that source, not independent verification by CAS.

Cross-source matching

PubChem molecular data are attached only when the returned InChIKey matches the ChEBI InChIKey exactly. When several PubChem records share that key, the lowest matching CID is used as the navigation reference. Source differences are retained. An InChIKey match cannot establish product grade, particle size, formulation or supplier equivalence.

Properties and conditions

ChEBI-reported mass and formula are shown separately from PubChem computed descriptors. No melting point, density, toxicity threshold, UN number or customs code is inferred from a CAS number. Missing data do not establish absence of a hazard.

Calculations and structure drawings

Mass-to-moles tools use n = m/M. Theoretical element mass fractions use a parseable source formula and atomic masses from the PubChem periodic table. Isotopically modified records are excluded from standard-weight mass fractions. Structure depictions are produced from source SMILES using RDKit; they are connectivity representations, not crystal structures or product images.

Safety information

NITE classification excerpts retain the jurisdiction, source ID and classification year. The selected year is the latest available year in the retrieved source compilation for that CAS. Classification details may depend on form or concentration. NIOSH references are occupational safety guides. Neither replaces the SDS issued for a specific commercial product.

Official links and web searches

Links labelled as records use retrieved record identifiers or source index mappings. Lookups and searches are labelled separately. Country-specific web searches use an exact CAS query restricted to the stated official domain. Search results are not treated as verified records.

Updates and corrections

This is the first release, checked 27 September 2026. Source publication dates and classification years are retained rather than replaced with the site’s publication date. Corrections can be submitted from each record; unresolved questions should be checked at the primary source.

Export and attribution

Record JSON, comparison CSV and search exports include source information. ChEBI-derived content is reused under CC BY 4.0. Retain source-specific terms when reusing exports.