CAS registry number

chemical identifier

A CAS registry number is a unique number given to every chemical substance by the Chemical Abstracts Service (CAS).[1] It is also called CASRN or CAS number. CAS registry number is also given to organic, inorganic compounds, minerals, isotopes, alloys. They are numbers ending with a check digit. They do not contain any structure information of the chemical.[2]

It now identifies more than 164 million organic and inorganic substances. 68 million protein and DNA sequences are identified also.[2] It is updated with around 15,000 new substances everyday.[1]


  1. 1.0 1.1 "CAS REGISTRY - The gold standard for chemical substance information". CAS. Retrieved 2020-09-24.
  2. 2.0 2.1 "CAS REGISTRY and CAS Registry Numbers". 2008-07-25. Archived from the original on 2008-07-25. Retrieved 2020-09-24.{{cite web}}: CS1 maint: bot: original URL status unknown (link)