CAS Registry Number

A CAS Registry Number, also referred to as CASRN or CAS Number, is a unique numerical identifier assigned by Chemical Abstracts Service (CAS) to every chemical substance described in the open scientific literature (currently including those described from at least 1957 through the present), including organic and inorganic compounds, minerals, isotopes, alloys and nonstructurable materials (UVCBs, of unknown, variable composition, or biological origin).

The Registry maintained by CAS is an authoritative collection of disclosed chemical substance information. Currently the CAS Registry identifies more than 102 million organic and inorganic substances and 66 million protein and DNA sequences, plus additional information about each substance. The Registry is updated with an approximate 15,000 additional new substances daily.

Use

Historically, chemicals have been identified by a wide variety of synonyms. Frequently these are arcane and constructed according to regional naming conventions relating to chemical formulae, structures or origins. Well-known chemicals may additionally be known via multiple generic, historical, commercial, and/or black-market names.