CAS registry number

From Atkinspedia

CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. They are also referred to as CAS numbers, CAS RNs or CAS #s.

Chemical Abstracts Service (CAS), a division of the American Chemical Society, assigns these identifiers to every chemical that has been described in the literature. The intention is to make database searches more convenient, as chemicals often have many names. Almost all molecule databases today allow searching by CAS number.

As of June 29, 2006, there were 28,482,118 substances in the CAS registry — the current number is published here. Around 50,000 new numbers are added each week.

CAS also maintains and sells a database of these chemicals, known as the CAS registry.