CAS Registry Number
Also known as CAS, CAS RN
chemical identifier
AI overview
A CAS Registry Number is a unique numerical identifier assigned to every chemical substance by the Chemical Abstracts Service, making it possible to clearly distinguish one chemical from another regardless of what language or naming system is used. This standardized system matters because it ensures scientists, manufacturers, and regulators worldwide can accurately reference and track specific chemicals without confusion.
AI-generated from the Wikipedia summary — may contain errors.
Article
Screenshot of the CAS Common Chemistry database with information about caffeine (58-08-2)
A CAS Registry Number (also referred to as CAS RN or informally CAS Number) is a unique identification number, assigned by the Chemical Abstracts Service (CAS) in the US to every chemical substance described in the open scientific literature, in order to index the substance in the CAS Registry. This registry includes all substances described since 1957, plus some substances from as far back as the early 1800s. It is a chemical database that includes organic and inorganic compounds, minerals, isotopes, alloys, mixtures, and nonstructurable materials (UVCBs - substances of unknown or variable composition, complex reaction products, or biological origin). CAS RNs are generally serial numbers (with a check digit), so they do not contain any information about the structures themselves the way SMILES and InChI strings do.