Each CAS Registry Number (often referred to as a CAS Number):
  • Is a unique numeric identifier

  • Designates only one substance

  • Has no chemical significance

  • Is a link to a wealth of information about a specific chemical substance

A CAS Registry Number is a numeric identifier that can contain up to 10 digits, divided by hyphens into three parts. The right-most digit is a check digit used to verify the validity and uniqueness of the entire number. For example, 58-08-2 is the CAS Registry Number for caffeine. 

Learn more about CAS numbers