How to Find CAS Registry Numbers
for Chemical Compounds
What is the CAS Registry Number? Why do I need it?
Chemical Abstracts Service (CAS) has a registry system for all completely identified chemical compounds or substances. There are over 128 million chemical substances & sequences currently registered and 12,000 new substances are added every day!! Each individual chemical substance is assigned a CAS Registry Number which may be thought of as that substance's "Social Security number." (For more information, see What does a CAS Registry Number look like?) The rules of chemical nomenclature frequently change and each chemical substance is liable to have several names: i.e. trade or brand name(s); generic or common name(s); trivial or semisystematic name(s); and systematic or IUPAC name(s). For example, Tylenol is a brand name for acetaminophen which is itself a trivial name. The systematic name for this analgesic compound is Acetamide, N-(4-hydroxyphenyl)-. Another systematic name for this same compound is 4'-Hydroxyacetanilide. There is just one CAS registry number which is 103-90-2. Even if other names are created for this compound, the registry number will remain unchanged. There is no structural significance to the registry number - it is simply an identifier.
The most efficient and complete way to search for chemical substances in the Chemical Abstracts Online database is to use the CAS registry number(s). A registry number may be searched as if it were a word, i.e., s 103-90-2 will search for information on Tylenol. See Using Native Commands to Search Chemical Abstracts Online for more information on searching techniques.
CAS registry numbers are found in several print and electronic sources. These sources should be consulted before you develop your search strategy for Chemical Abstracts Online. It is a good idea to verify registry numbers found in sources not published by CAS. This is because the registry number could represent some other form of the compound (e.g., stereoisomer, salt, or an incompletely defined form) than the one you want. To verify the registry number, select the Registry File by typing file reg into the search box in Chemical Abstracts Online. Enter s ###-##-# into the search box (###-##-# is the registry number - fill in the digits for the compound of interest). Check the record retrieved and make certain it is the desired substance before you use it in searching Chemical Abstracts Online.
If the substance retrieved is not the one you want or you cannot find the CAS registry number in any of the sources listed below, you may then search the Registry File by substance name or molecular formula. A structure search may be attempted if all else fails but this type of search is expensive and can be complicated.
What sources contain CAS Registry Numbers?
- Chemical Abstracts Index Guide. Columbus, OH: Chemical Abstracts Service, 1967-96 (ref QD 1 A51) There is an Index Guide for each collective 5-year period of Chemical Abstracts. The Index Guide is published every 18 months and cumulated at the end of each collective period. This is the "authority" list for both the print and online versions of Chemical Abstracts.
- Buyer's Guide for Chemicals - A directory of suppliers of chemicals and chemical products. More than 295,000 products are searchable by product name. (http://www.buyersguidechem.de)
- ChemExper Chemical Directory - You may search this database of "chemicals available in the world" by registry number, molecular formula or by chemical name or synonyms in different languages. (http://www.chemexper.com/)
- ChemSpider - Claims to be the "the richest single source of structure-based chemistry information" covering over 25 million compounds from almost 400 sources. You may search by systematic name, synonym, trade name, CAS registry number, etc. and find a wealth of information, including the CAS registry number. (http://www.chemspider.com)
- CRC Handbook of Chemistry and Physics. Cleveland, OH: CRC Press, published annually (ref QD 65 H3) *Older editions are in circulating collection (QD 65 H3).
- Gardner, William, Gardner's Chemical Synonyms and Trade Names, 11th ed. Brookfield, VT: Gower, 1999 (ref TP 9 G286 1999)
- Hawley, Gessner Goodrich, et al, Hawley's Condensed Chemical Dictionary, 15th ed. NY: Van Nostrand Reinhold, 2007 (ref QD 5 C5 2007)
- Howard, Philip H. & Neal, Michael, Dictionary of Chemical Names and Synonyms, Boca Raton, FL: Lewis Publishers, 1992 (ref TP 9 H65 1992)
- Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed. NY: Wiley, 1978-84 (ref TP 9 E685 1978) 25 volumes plus supplement.
- Kirk-Othmer Encyclopedia of Chemical Technology, 4th ed. NY: Wiley, 1991 (ref TP 9 E685 1991) 25 volumes plus supplements.
- NIST Chemistry WebBook- A gateway to the data collections of the National Institute of Standards and Technology (NIST), you can search for data on specific compounds by name, chemical formula, CAS registry number, molecular weight, or selected ion energetics and spectral properties. (http://webbook.nist.gov/)
- WIKIPEDIA (http://wikipedia.org) - "The Free Encyclopedia" has articles on chemical compounds written by and for chemists. Articles usually include CAS registry number and structural diagrams as well as alternate names, identifiers and properties with links to other sources of information.
- Aldrich Chemical Company, Aldrich Chemistry : Handbook of Fine Chemicals, Milwaukee, WI: Sigma-Aldrich (ref TP 202 A38)
- Fisher Scientific - You may search the Fisher Scientific chemical catalogs by chemical name, molecular formula, catalog number, or key word. Choose "Advanced Search" to get all of the search options. Contains over 2,400 chemicals and material safety data sheets (MSDS's). (https://www.fishersci.com)
- Sigma-Aldrich Corporation Home Page - Sigma-Aldrich has an advanced search page that allows you to search by chemical or product name, by registry number, by molecular formula, etc. (http://www.sigmaaldrich.com/united-states.html)
- Sigma Chemical Company, Biochemicals, Reagents & Kits for Life Science Research, St. Louis, MO: Sigma Chemical Co. (ref TP 202 S54)
- Spectrum Chemicals & Laboratory Products - You may search Spectrum Chemicals by chemical name, keyword, CAS registry number, FEMA number, color index number, and molecular formula. (http://www.spectrumchemical.com/)
- WWW Chemicals - Another searchable collection of chemical catalogs which may be searched by chemical name, CAS registry number, field of expertise, molecular formula, etc. (http://www.chem.com/catalogs/)
- Dictionary of Inorganic Compounds, 1st ed. NY: Chapman and Hall, 1992 (ref QD 148 D53 1992) 5-volume set and 1st-2nd annual supplements.
- CRC Handbook of Data on Organic Compounds, 2nd ed. Boca Raton, FL: CRC Press, 1989 (ref QD 257.7 H36 1989) 10 volume set.
- Dictionary of Organic Compounds, 5th ed. NY: Chapman and Hall, 1982 (ref QD 246 D5 1982) 7 volume set and 1st-10th annual supplements (1982-1992).
- Handbook of Physical Properties of Organic Chemicals, Boca Raton, FL: CRC Press, 1997 (ref QD 257.7 H374 1997)
- Pedley, J.B. Thermochemical Data of Organic Compounds, 2nd ed. NY: Chapman and Hall, 1986 (ref QD 511.8 P43 1986)
DRUGS AND BIOLOGICALLY IMPORTANT COMPOUNDS
- Dictionary of Alkaloids, London: Chapman and Hall, 1989 (ref RS 431 A53 D53 1989) 2 volume set. According to the introduction, it "includes most naturally occurring, nitrogen-containing secondary metabolites of plant, microbial, or even animal origin."
- Merck Index, Rahway, NJ: Merck & Co., published every 7-8 years (ref RS 51 M4) Library has latest three editions - latest edition is at the Reserve Desk.
- PubChem - A set of three databases: PubChem Compound, PubChem Substance, and PubChem Bioassay. PubChem provides information on the biological activities of small molecules. Depending on the source of the data, the results can include registry numbers but may not identify them as such. (http://pubchem.ncbi.nlm.nih.gov/).
- Briggs, Shirley A. Basic Guide to Pesticides: their characteristics and hazards, Washington, DC: Hemisphere, 1992 (ref SB 951 B75 1992)
- Crop Protection Handbook, Willoughby, OH: Meister PubCo, published annually. HSU Library has 2005 edition. (ref S 633 A5)
- EXTOXNET (Extension Toxicology Network) - A cooperative effort of UC Davis, Oregon State University, Michigan State University, Cornell University, and the University of Idaho - contains over 130 Pesticide Information Profiles on specific pesticides. (http://ace.orst.edu/info/extoxnet/ghindex.html)
- Montgomery, John H. Agrochemicals Desk Reference, 2nd edition. Boca Raton, FL: CRC Press, 1997 (ref TD 196 A34 M66 1997)
- National Pesticide Information Center (NPIC) - NPIC's mission is "to serve as a source of factual, unbiased information on pesticide chemistry, toxicology, and environmental fate." In addition to other information, NPIC has "active ingredient" fact sheets. (http://npic.orst.edu)
- Pesticide Index: an index of chemical, common and trade names of pesticides and related crop- protection products, Nottingham, England: Royal Society of Chemistry, 1988 (ref SB 950.95 P47 1988)
- Worthing, Charles R. The Pesticide Manual, 9th ed. Surrey, UK: British Crop Protection Council, 1991 (ref SB 951 P434 1991)
TOXIC OR HAZARDOUS SUBSTANCES
- ACToR: Aggregated Computational Toxicology Resource - From the National Center for Computational Toxicology of the Environmental Protection Agency (EPA), this resource has data (both quantitative and qualitative) from a large number of sources (called data collections), including EPA databases, PubChem, other NIH and FDA databases, state and other national sources, and from academic groups. You may search by chemical name, CAS Registry Number, or structure. (http://actor.epa.gov/actor/)
- Beim, Howard J. Rapid Guide to Hazardous Air Pollutants. NY: Van Nostrand Reinhold, 1998 (ref TD 883.1 B37 1998)
- Book of Lists for Regulated Hazardous Substances, 10th ed. Rockville, MD: The Institutes, 2001 (ref TD 1032 B66 2001)
- Bretherick, L., Bretherick's Handbook of Reactive Chemical Hazards, 6th ed. Oxford ; Boston : Butterworth-Heinemann, 1999 (ref T 55.3 H3 B73 1999)
- Bretherick, L., Hazards in the Chemical Laboratory, 4th ed. London: Royal Society of Chemistry, 1986 (ref QD 51 H35 1986)
- Calabrese, Edward J. & Kenyon, Elaina M., Air Toxics and Risk Assessment. Chelsea, MI: Lewis Publishers, 1991 (ref RA 576.5 C35 1990)
- The Chemical Database - You may search this database of over 30,000 hazardous chemicals by chemical name, synonyms, formula, and registry number (including CAS, DOT, RTECS, EINECS, PubChem, Beilstein and Merck). (http://ull.chemistry.uakron.edu/erd)
- Forum for Scientific Excellence, Inc., Compendium of Hazardous Chemicals in Schools and Colleges. Philadelphia, PA: Lippincott, 1990 (ref T 55.3 H3 C646 1990)
- Forum for Scientific Excellence, Inc., Cross-reference Index of Hazardous Chemicals, Synonyms, and CAS Registry Numbers. Philadelphia, PA: J.B. Lippincott, 1990 (ref T 55.3 H3 C76 1990)
- Forum for Scientific Excellence, Inc., Index of Hazardous Contents of Commercial Products in Schools and Colleges. Philadelphia, PA: J.B.Lippincott, 1990 (ref T 55.3 H3 I53 1990) Excellent way to find chemical components of trade name products.
- Household Products Database - A database of health and safety information on household products and their ingredients. If you choose Advanced Search, you may search ingredients by chemical name or CAS registry number. You may also search by product name or health effects. (http://hpd.nlm.nih.gov)
- Keith, Lawrence H. & Walker, Mary M., Handbook of Air Toxics: sampling, analysis, and properties. Boca Raton, FL: Lewis Publishers, 1995 (ref TD 890 K4 1995)
- Kokoszka, Leopold, C., Environmental Management Handbook: toxic chemical materials and wastes. NY: Marcel Dekker, 1989 (ref TD 1032 K65 1989)
- Lefevre, Marc J. & Conibear, Shirley A., First Aid Manual for Chemical Accidents, 2nd Engl. lang. ed. NY: Van Nostrand Reinhold, 1989 (ref RC 963.3 L4313 1989)
- Lewis, Richard J., Sr., Carcinogenically Active Chemicals: a reference guide. NY: Van Nostrand Reinhold, 1991 (ref RC 268.6 L48 1991)
- Lewis, Richard J., Sr., Food Additives Handbook. NY: Van Nostrand Reinhold, 1989 (ref RA 1270 F6 L49 1989)
- Lewis, Richard J., Sr., Hazardous Chemicals Desk Reference, 5th ed. NY: Wiley, 2002 (ref T 55.3 H3 L49 2002)
- Lewis, Richard J., Sr., & Sax, N. Irving, Sax's Dangerous Properties of Industrial Materials, 10th ed. NY: Wiley, 2000 (ref T55.3 H3 L494 2000) 3-volume set
- Mackay, Donald, et al, Illustrated Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals. Boca Raton, FL: Lewis Publishers, 1992-1997 (ref TD 196 O73 M32 1992) 5-volume set
- Mahn, William J., Academic Laboratory Chemical Hazards Guidebook. NY: Van Nostrand Reinhold, 1991 (ref QD 51 M29 1991)
- Material Safety Data Sheets - A collection of sites where you can get MSDS's. Most of these sites are searchable by chemical name, manufacturer name, and/or CAS registry number. (http://jrm.phys.ksu.edu//Safety/msds.html)
- Montgomery, John H. & Welkom, Linda M., Groundwater Chemicals Desk Reference, 3rd ed. Chelsea, MI: Lewis Publishers, 2000 (ref TD 426 M66 2000)
- National Institute for Occupational Safety and Health, NIOSH Pocket Guide to Chemical Hazards. Cincinnati, OH: NIOSH, 1997 (Docs HE 20.7108:C42/997)
- Pohanish, Richard P., Wiley Guide to Chemical Incompatibilities, 2nd ed. Hoboken NJ: J. Wiley, 2003 (ref T 55.3 H3 P647 2003)
- Pohanish, Richard P., Rapid Guide to Hazardous Chemicals in the Environment. NY: Van Nostrand Reinhold, 1997 (ref RA 1226 P64 1997)
- Pohanish, Richard P., Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, 4th ed. Park Ridge, NJ: Noyes Publications, 2002 (ref RA 1215 .S58 2002) 2-volume set
- Proctor, Nick H., Proctor and Hughes' Chemical Hazards of the Workplace, 4th ed., NY: Van Nostrand Reinhold, 1996 (ref RA 1229 P76 1996)
- Sheftel, Victor O., Handbook of Toxic Properties of Monomers and Additives. Boca Raton, FL: Lewis Publishers, 1995 (ref RA 1242 P66 S54 1995)
- Shepard, Thomas H., Catalog of Teratogenic Agents, 11th ed. Baltimore, MD: Johns Hopkins University Press, 2004 (ref QM 691 S53 2004)
- Sittig, Marshall, World-Wide Limits for Toxic and Hazardous Chemicals in Air, Water and Soil. Park Ridge, NJ: Noyes Publications, 1994 (ref RA 1229.5 S58 1994)