How it works
A CAS number is a string of up to ten digits in three hyphen-separated parts (for example, 68-19-9), where the final digit is a check digit computed from the others. The check digit lets software catch a mistyped number, but it does not confirm that the number was assigned to the substance you have in mind.
The number is assigned by the Chemical Abstracts Service, not derived from structure, so it cannot be computed from a formula or a sequence — it must be looked up. Different salts, hydrates, or stereoisomers of a substance generally receive different CAS numbers, which is why a CAS number is more specific than a name.
Not every substance has one. Newer research peptides and blends may have no assigned CAS number at all; where a Lineará record has none, the field reads with an em dash rather than a guessed value.
Why it matters
A CAS number is the most reliable way to confirm that two documents refer to the same substance. Names drift — synonyms, brand names, abbreviations — but the CAS number is a single controlled identifier, which is why certificates and identity records cite it.
Because it is substance-specific down to salt and stereochemistry, a CAS number can distinguish forms that share a name, guarding against the ambiguity a plain name invites.
It is a pointer, not a proof: a CAS number tells you which substance is claimed, not that the material in hand matches it. That match is what the analytical methods — ESI-MS and RP-HPLC — establish.
At Lineará
Where a compound has an assigned CAS number, it is published on its compound page and on every certificate of analysis, alongside the molecular formula and molecular weight.
The identifier set is emitted as loaded, never guessed: a compound with no assigned CAS number shows an em dash, not a fabricated string.