What is a CAS number, how is it assigned and why it’s so important?

What is a CAS number?

CAS (Chemical Abstracts Service) also known as CASRN is a registry of chemical identification numbers maintained by the American Chemical Society. Although ceramic materials are generally minerals or processed minerals rather than chemicals, most do have numbers in the system. Currently there are over 182 million CAS registration numbers that have been assigned to a chemical substance. CAS numbers provide a simple, consistent and reliable way of identifying chemical substances so that they are recognisable regardless of your region.


What Is A CAS Registry Number (CAS RN)?

CAS REGISTRY covers substances identified from the scientific literature from 1957 to the present, with additional substances going back to the early 1900s. A CAS Registry Number is a unique and unambiguous identifier for a specific substance that allows clear communication and, with the help of CAS scientists, links together all available data and research about that substance. Governmental agencies rely on CAS Registry Numbers for substance identification in regulatory applications because they are unique, easily validated, and internationally recognized.

As of 2020, the CAS Registry® contained over 159 million unique chemical substances, as well as about 70 million protein and nucleic acid sequences. In April 2021, CAS announced it had registered its 250 millionth unique chemical substance.


How does CAS assign Registry numbers?

A CAS Registry Number is assigned to a substance when it enters the CAS REGISTRY database. Numbers are assigned in sequential order to unique, new substances identified by CAS scientists for inclusion in the database.

A CAS Registry Number is separated by hyphens into three parts, the first consisting of up to seven digits, the second consisting of two digits and the third consisting of a single digit.


What kinds of compounds does the CAS Registry contain?

CAS Registry contains a wide variety of substances, including the world’s largest collection of:

  • Organic and inorganic compounds
  • Metals and alloys
  • Minerals
  • Coordination compounds and Organometallics
  • Elements, Isotopes, and Nuclear particles
  • Proteins and nucleic acids
  • Polymers
  • Non-structurable materials and those of unknown or variable composition and biologics (UVCBs)


Why is CAS number important?

The CAS number prevents those errors by assigning a unique identifier to all chemical substances, and all their various written names. Every SDS needs a CASRN and that number can even be added to a GHS label for extra clarity. Overall, CAS numbers are an important part of hazard identification because it directs the user to the right information needed to stay safe in the presence of hazardous substances.

Overall, CAS identification numbers are an essential part of workplace safety when it comes to recognizing danger and preventing accidents from happening.

For assistance with any of these or for answers to your questions about the safety, storage and labelling of your chemicals, contact us.