This article was accepted into the corpus but its outbound wikilinks were never NER-processed — typical at the deepest BFS hop or when the run's entity cap was reached. No expansion funnel to show.
| CAS Registry Number | |
|---|---|
| Name | CAS Registry Number |
| Caption | Chemical Abstracts Service registry identifier |
| Introduced | 1965 |
| Organization | Chemical Abstracts Service |
| Format | numeric (up to 10 digits) with hyphens |
| Example | 58-08-2 |
CAS Registry Number The CAS Registry Number is a unique numeric identifier assigned to chemical substances to facilitate unambiguous reference in scientific, industrial, and regulatory contexts. It was created and is maintained by the Chemical Abstracts Service, a division of the American Chemical Society, and is widely used across databases, patents, safety data sheets, and regulatory lists. The identifier is distinct from systematic nomenclature and trade names, serving as a compact cross-reference for researchers, corporations, and agencies.
The system originated at the Chemical Abstracts Service in the 1960s as part of efforts by the American Chemical Society and its Chemical Abstracts Service unit to manage an expanding corpus of chemical literature and patent disclosures. Early drivers included coordination with indexing efforts at the United States Patent and Trademark Office and the needs of pharmaceutical firms such as Merck & Co., Pfizer, and GlaxoSmithKline for reliable substance cross-referencing. International organizations like the International Union of Pure and Applied Chemistry and regulatory bodies including the European Chemicals Agency and the United States Environmental Protection Agency later integrated the identifiers into harmonized data workflows. Adoption grew through linkage with bibliographic resources such as SciFinder and integration into databases maintained by entities like PubChem, TOXNET, and major publishers including Elsevier and Wiley.
A CAS Registry identifier consists of up to three groups of digits separated by hyphens: a sequence of up to six digits, a two-digit group, and a single check digit. The check digit is computed via a modulo operation on the concatenated numeric sequence, enabling validation in systems used by firms including IBM, Siemens, and Bayer. Examples used in literature include identifiers for compounds catalogued by laboratories at institutions such as Harvard University, Massachusetts Institute of Technology, and Stanford University. The format is independent of chemical classification schemes promulgated by bodies like the International Organization for Standardization and differs from identifiers such as the InChI managed by the IUPAC-aligned community.
Assignment of an identifier occurs when a substance is entered into the registry following submission from publishers, patent offices, or corporate research groups including Roche, Novartis, and government laboratories like National Institutes of Health. CAS curators use structural information, literature citations, and patent sequences to determine whether a new registry entry is required. Maintenance involves merging synonymous records, splitting ambiguous entries, and updating registry metadata, processes performed by curators collaborating with organizations such as the World Health Organization, national chemical inventories like those of Japan and Canada, and commercial vendors like ChemSpider and Elsevier.
CAS identifiers are used extensively in scholarly indexing, patent prosecution at offices such as the European Patent Office and the United States Patent and Trademark Office, regulatory compliance workflows at agencies like the Environmental Protection Agency and European Chemicals Agency, supply chain management by companies such as 3M and Dow Chemical Company, and safety documentation produced by firms like ExxonMobil. They appear in scientific articles published in journals from publishers like Nature Publishing Group, Springer, and American Chemical Society journals, and are integrated into laboratory information management systems at institutions including Laboratory Corporation of America and academic core facilities. CAS numbers facilitate interoperability between chemical registries such as PubChem, ChEMBL, and DrugBank.
Critiques of the system have focused on proprietary control by a division of the American Chemical Society, limited public access compared with open identifiers promoted by groups including the Open Knowledge Foundation and projects like Wikidata. Scholars and organizations such as Greenpeace and some academic consortia have argued for greater transparency and open alternatives to reliance on a single commercial registry. Technical limitations include challenges representing mixtures, polymers, naturally derived material from institutions like Smithsonian Institution collections, and certain supramolecular assemblies encountered in research at universities such as Caltech and University of Cambridge.
The registry and associated services such as SciFinder are commercial offerings of the American Chemical Society; licensing, access, and usage are governed by contracts with publishers, corporations, and government agencies. Litigation and policy debates involving intellectual property, data licensing, and public access have engaged stakeholders including major publishers like Elsevier and Springer Nature, as well as national research libraries and universities such as Library of Congress and British Library. Commercial use in product labeling, marketing, and safety compliance is subject to regulatory frameworks administered by agencies like the Food and Drug Administration and European Medicines Agency.
Well-known CAS identifiers include those for historically significant and widely studied chemicals catalogued in patents and literature: the identifier associated with caffeine is routinely cited in biochemical research at institutions such as Johns Hopkins University and Yale University; analgesics and active pharmaceutical ingredients referenced by companies like Johnson & Johnson and Bayer rely on CAS identifiers in regulatory filings to agencies such as the FDA; and substances restricted under international treaties administered by bodies like the United Nations and Organisation for the Prohibition of Chemical Weapons are tracked in part via registry numbers. Special cases include broad entries for complex mixtures, polymers curated with input from industry consortia like PlasticsEurope, and botanically derived extracts documented by botanical gardens such as the Royal Botanic Gardens, Kew.
Category:Chemical identifiers