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.