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All that you Need to Know about CAS Numbers

The American Chemical Society (ACS) has a division named the Chemical Abstracts Service (CAS). They are a source for accurate scientific information, namely, to find a CAS Number on a specific chemical substance.

What is a CAS Number? What is its Format?

The CAS Registry is a substance collection containing information on many chemicals. Furthermore, it is updated daily and is relied upon by many experts like scientists, manufacturers, and regulators. Also, the registry links to all relevant publications, chemical suppliers, formulations, reactions, and data on the molecules of interest.


Additionally, compounds in this registry are classified using a CAS Registry Number (CAS RN), or simply called CAS number. It has the following characteristics:

  • A distinctive numerical identifier for each chemical substance
  • It has no chemical significance.
  • It contains up to 10 digits separated into three parts by two hyphens:
      •  The first part of the CAS Number contains two to seven digits.
      •  The second part of the CAS RN contains two integers.
      • The third part of the number holds a single check digit (to verify the validity of a CAS number).
CAS Registry Number

Common CAS Numbers of Restricted Substances in Products

Please find the CAS Numbers of common regulated compounds within products:

Substance Name














These chemicals are restricted under the following regulations:

Where can I find the CAS Numbers of a Substance?

CAS Common Chemistry is a free resource to discover information such as the name(s), molecular formula, and the physical and chemical properties of substances found on the CAS Registry.

Indeed, you can input any of the following information to obtain the required information of your substance of interest:

Possible Inputs


Compound Name

Bisphenol A

CAS Registry Number (CAS RN)


The Simplified Molecular Input Line Entry System (SMILES)


The International Union of Pure and Applied Chemistry (IUPAC) International Chemical Identifier (InCHI)


Thus, this is a reputable source to either determine the name of a substance with a particular CAS Registry Number or to find the CAS RN of a known molecule.

What is the Benefit of using a CAS Number?

Safety Data Sheets SDS

CAS Registry Numbers are practical for Safety Data Sheets (SDS) and Full Material Disclosures (FMD). Indeed, many molecules have many names depending on the region of the world and their preferred chemical nomenclature. Therefore, since every different substance has a unique CAS Registry Number, we can now ensure that we are identifying the molecule at hand without error. Consequently, CAS numbers are an international resource and standard across many industries and regulatory agencies.

Namely, these known agencies frequently use CAS Registry Numbers in their works:

  • ECHA
  • EPA
  • CalEPA

What are the Disadvantages of using a CAS Number?

Using Imprecise CAS Numbers

Some confusion can arise when working with CAS numbers for classes of compounds. For example, the CAS RN 7439-92-1 applies to the lead element. However, some suppliers will list CAS RN 7439-92-1 for lead and lead compounds in an FMD or an SDS. Nevertheless, this class of substances does not possess a CAS number. Therefore, this can lead to less transparency in the industry.

Lead California Proposition 65

Using a CAS Number of Elements instead of Molecules

Finally, some FMDs display the CAS number of elements (atoms) from the periodical table, not to mention the CAS numbers of molecules made of these elements. As a result, restricted molecules may not appear.

Periodical Table

Do you have more questions on CAS Registry Numbers? Contact Enviropass for the latest news!