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Where to find...

Chemical information can be complex, and this Guide is intended to help you find sources that will answer your questions.  The tabs below highlight the most commonly sought types of chemical information.  The pages listed to the left go deeper into the available resources on specific topics and key tools. 

Index Databases

If you already have a reference:


Chemistry doesn't have a strong preprint tradition, but these archives provide platforms for the free deposit and dissemination of articles prior to publication.

There are many, many tools out there where you can "look up" a chemical name or structure.  This is just a selection of some of the better known ones.  Most also contain various types of factual data about chemical substances - properties, safety hazards, etc. 

Chemical Nomenclature

Chemical Abstracts Service has registered millions of chemical substances since 1965. CAS Registry Numbers (RNs) are very useful when searching for information about a specific chemical structure, as well as polymers, mixtures, alloys, and substances whose exact formula is unknown or variable. CAS has also registered tens of millions of biosequences.

A Registry Number (RN) looks like this:


where the first segment can be from two to seven digits long, followed by two digits, then a single check-digit. It is a sequential accession number from the CAS Registry database. The RN carries no chemical or structural meaning in itself. It is simply an identifier for a specific substance that CAS has registered during the process of indexing the literature (or added from another source). The shorter the first segment, the older the registration and the more common (and probably better described) the compound is.


Using Registry Numbers as Search Terms

A Registry Number allows you to avoid using chemical names when searching for information about a compound. If you have a RN in hand, use it as a search term in SciFinder, in place of a chemical name. Most non-bibliographic chemical databases also allow searching by Registry Number.


Registry numbers are useful substitutes for names, but they are not perfect.

  • CAS' registration policies are complex and highly specific. This is especially true for substances with undefined structures, commercial formulations, polymers, mixtures, inorganic substances (separate RNs are assigned for ions, charge states, hydration states, etc.), drugs (separate RNs for the free base and HCl forms), and for organic salts and stereoisomers.
  • RNs used in non-CAS resources, such as supplier catalogs, MSDS, handbooks, encyclopedias, and databases, may not be correctly assigned, and often are not checked for accuracy or updated to reflect changes. When in doubt, verify a Registry Number in SciFinder.
  • While a de facto standard for chemical identification, CAS RNs are proprietary. Any systematic use of RNs in a third-party database requires a license.

Where to Find Registry Numbers

Many printed and online reference sources about chemicals use CAS Registry Numbers as a standard identifier.

See our guide to Spectra and Spectral Data.

There are many search engines and portals that provide free access to patent documents from agencies around the world. They are mainly useful for locating a patent document you already know about. They are not intended for patentability or prior-art searching, which should be done by professional patent searchers. Most patent office public search sites have poorly designed interfaces, so patience and determination are essential. Pay special attention to the entry format of patent numbers: most databases won't tolerate any variation in the parsing of numbers and country codes.

Technical reports usually originate in federal government agencies, but may also come from academic institutions, state or foreign governments, and private firms and organizations. They contain results of research carried out in government labs or on government contracts or, in the case of private companies, for in-house, proprietary use. They are often cited in the literature and indexed in databases by complex report numbering systems, and they can be difficult to obtain.  Consult a librarian when you need help.

See the page on Safety, Hazards, Environment for information about sources of MSDS.

Here's a selection of catalog sites for laboratory-grade specialty chemicals.  Catalogs marked with metacatalog cover multiple suppliers and manufacturers.

(For industrial products and bulk commodity price information, see the guide on Chemical Engineering Economics.) 

See the guide on Citing Sources for more information about bibliographies and reference managers.

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Chemistry Librarian

David Flaxbart's picture
David Flaxbart
Mallet Chemistry Library
University of Texas Libraries

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