What Is a CAS Number?

What Is a CAS Number?

A CAS number is a unique number assigned by the Chemical Abstracts Service (CAS), a divison of the American Chemical Society, to chemical substances. Those include organic compounds, inorganic compounds, minerals, isotopes, allows, and nonstructural materials. There are over 160 million unique CAS numbers, each representing a unique chemical substance.  
 
A CAS number can also be called a “CAS registry number” or a “CASRN.”

For example, which of the following chemical identifiers would you find easier to use in a scientific publication or governmental regulation?
  1. 2-methoxy-1,3,3-trimethylbicyclo[2.2.1]heptane
  2. 248-269-5
They are both for the exact same substance. The second identifier is the CAS Registry Number.

Governmental agencies rely on them for substance identification in regulatory applications because they are unique, easily validated, and internationally recognized. So, it's important for compliance and EHS professionals to understand them. 

For more info, check out the CAS Registry: https://www.cas.org/

PubChem is also a good, free resource for substance identifiers: https://pubchem.ncbi.nlm.nih.gov/

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