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The CAS Registry Number

The CAS registry number
CAS REGISTRY contains more than 127 million unique organic and inorganic chemical substances, such as alloys, coordination compounds, minerals, mixtures, polymers and salts, and more than 66 million sequences—more than any other database of its kind.
When you need to positively identify a chemical substance, you can rely on the authoritative source for chemical names and structures of CAS REGISTRY. You can also identify your substance of interest by its CAS Registry Number® (, which is universally used to provide a unique, unmistakable identifier for chemical substances.


You can also use CAS REGISTRY to locate:
Literature references to the substance, experimental and predicted property data (boiling and melting points, etc.), CA Index Names and synonyms, commercial availability, preparative methods, spectra, and regulatory information from international sources
You can obtain the information you need for millions of substances from the most current and reliable collection of chemical substance information in the world, CAS REGISTRY.



  • Substances reported in the literature back to the early 1800s
  • Updated daily with about 15,000 substances
  • Substance information enriched with experimental and predicted property data, including more than 7.4 billion property values, data tags and spectra

Examples of CAS Registry numbers:
Benzene [71-43-2] 

1,2-Benzenedisulfonic acid, dipotassium salt [5710-54-3] 

Hexadimethrine bromide [28728-55-4]

Chemistry, Geosciences and Environmental Studies Librarian

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Emily Wild
212 Lewis Science Library