Chemical Abstracts Service (CAS)
Definition and meaning of Chemical Abstracts Service (CAS) in chemistry.
Chemical Abstracts Service (CAS) is a division of the American Chemical Society that catalogs chemical substances reported in the scientific literature and assigns each one a unique identifier called a CAS Registry Number.
In more detail
A CAS Registry Number lets chemists, regulators, and databases unambiguously identify one specific substance even when it goes by many different common names, trade names, or synonyms. Each number is an arbitrary, non-chemically-meaningful string of up to ten digits, written as two or more groups separated by hyphens, with the last digit acting as a check digit calculated from the others. Since CAS began registering substances in 1957, its database has grown to well over 200 million organic and inorganic compounds, and CAS numbers are now standard entries on safety data sheets (SDS), in government regulatory lists, and in chemical inventory systems worldwide.
Key facts
| Field | General Chemistry |
|---|---|
| Parent organization | American Chemical Society |
| Registry began | 1957 |
| Identifier format | CAS Registry Number, e.g. XXX-XX-X |
Water is registered as CAS number 7732-18-5, while ordinary table salt (sodium chloride) is 7647-14-5.
Frequently asked questions
Does a CAS number reveal a substance's chemical structure?
No. The number itself carries no chemical meaning; it is simply a unique lookup key that must be searched in the CAS registry to find the substance's name, formula, and structure.
Is a CAS number the same as an IUPAC name?
No. A CAS number is a unique numeric identifier assigned by CAS, whereas an IUPAC name is a systematic name derived from structural rules; a substance has one CAS number but may have several accepted names.