CAS Number
A CAS number is a unique ID that the Chemical Abstracts Service assigns to a chemical substance. It works like a serial number: one substance, one number.
Where the word comes from
CAS stands for Chemical Abstracts Service, a division of the American Chemical Society that has indexed the chemical literature since the early 1900s. An “abstract” — from Latin abstractus, “drawn away” — is a summary drawn out of a longer paper. The registry of unique substance numbers began in the mid-1960s, when the number of known chemicals outgrew indexing by name.
What it means here
Chemicals often carry several names at once — a research code, a chemical name, a common name — and the same name is sometimes used loosely for different substances. The CAS number removes that confusion. On a product page or a certificate of analysis, it lets a researcher confirm the exact substance being described and look it up in public databases such as PubChem, where its structure and identifiers are recorded.
Words you’ll see together
- PubChem CID — the matching ID for the same substance in the public PubChem database
- molecular formula — the count of each type of atom, listed beside the CAS number
- molecular weight — the substance’s mass value, another identity check on the same line
- sequence — for a peptide, the ordered list of amino acids the identifiers describe
Related terms
- Molecular weight — another identity check listed beside the CAS number
- Certificate of Analysis — the document where the CAS number confirms what was tested
- Peptide — the class of substance these identifiers describe on our pages
Where it appears in our catalog
- BPC-157 — identifiers listed in the product’s technical details
- GHK-Cu — a compound with several common names, pinned down by one CAS number
- Certificates of Analysis FAQ — matching identifiers between vial and report
References
- PubChem, National Library of Medicine — public database of chemical substances and their identifiers. pubchem.ncbi.nlm.nih.gov
