The CAS Registry Number (or CAS RN or CAS Number) is a unique numeric identifier assigned by the Chemical Abstracts Service (CAS) to chemicals reported in the published literature. They can contain up to 10 digits and take the form of XXXXXXX-XX-X. For example, 9002-84-0 is the CAS RN for Teflon. The CAS RN can be used to search a number of chemistry resources. More information about the CAS RN can be found at:
