CAS Registry Numbers
CAS Registry Numbers are an important tool for substance searching. These are unique identifiers assigned by the Chemical Abstracts Service (CAS) to specific substances identified by them in the chemical literature.
Registry Numbers save you from having to think of all the different synonyms, trade names, or possible systematic names when you are doing a compound search by linking them all into a single search term.
For example, there are over 20 synonyms for formaldehyde, e.g., methanal, formalin, methyl aldehyde. The CAS Registry Number for it, 50-00-0, is specific to all those names for the same compound.
If you know the chemical name of a compound but would like to find its CAS Number, we suggest trying the resources listed in the 'Related Links' section below. For the most effective search, try them in the following order:
- ESIS (European chemical Substance Information System)
- RSC ChemSpider
- NIST Chemistry WebBook
If none of these resources contain the information you are looking for, email us and we will try our resources such as Chemical Abstracts (RSC members only).
We can also search the CAS Registry database which is the definitive source of CAS Numbers. This is useful for checking CAS Numbers as well as searching by chemical name. Charges apply for searching the CAS Registry database. Please email us if you would like a quote (both RSC members and non-members).
CAS Registry and CAS Registry Numbers
Detailed description of the CAS Registry, frequency of update and their importance.
CAS Registry Database Summary Sheet
The CAS Registry database is the definitive source for finding CAS Numbers.
Provides access to structure and nomenclature authority files used for the identification of chemical substances cited in National Library of Medicine (NLM) databases, including the TOXNET system. ChemIDplus also provides structure searching and direct links to many biomedical resources at NLM and on the internet for chemicals of interest. The database contains over 380,000 chemical records, of which over 269,000 include chemical structures, and is searchable by Name, Synonym, CAS Registry Number, Molecular Formula, Classification Code, Locator Code, Structure, and/or Biological/Chemical properties. You can also instantly check the validity of any CAS Registry Number you have been given.
European chemical Substances Information System.
NIST Chemistry WebBook
Thermochemical, spectroscopic, thermophysical and energetics data from the US National Institute of Standards and Technology.
Search nearly 25 million chemical structures and their properties, patents, publications and more
Produces and sells a broad range of biochemicals, organic and inorganic chemicals and related products. Parent company of Sigma, Aldrich, Fluka and Supelco.
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