Teaching Chemical Information:
Tips and Techniques

— August 1998 —

Chemical Literature (Chem 184/284)
University of California at Santa Barbara

Lecture 10: Chemical Abstracts in Print, Part 2

Concept Indexing in Chemical Abstracts

• Weekly issues use keyword indexing assigned by the indexer. Terms are not systematically selected.
• Volume and Collective Indexes use systematic indexing for both general concepts and chemical substances.

Keyword Indexing

• Keywords are assigned by the indexer based on the body of the document, not just the title or abstract.
• Terms are often abbreviated, following the standard CA abbreviations.
• To save space, a keyword is not assigned if it’s part of the section heading for the section the abstract appears in, e.g. “Steroids”.
• Additional keywords are listed beneath the main keyword heading to flesh out the concept (like the co-terms in Science Citation Index).
• Chemical names are listed along with concept terms in the issue indexes. The chemical names are not systematic, but follow the author’s nomenclature.
• Example
  Article title: “Facile preparations of 4-fluororesorcinol”
  • Acetophenone
    methoxy fluorination regiochem
  • Benzene
    fluoro dihydroxy
  • Deacetylation
    demethylation fluorodimethoxyacetophenone
  • Demethylation
    fluorodimethoxybenzene
  • Methoxybenzene
    methoxyacetophenone fluorination regiochem
  • Fluorodihydroxybenzene
  • Fluororesorcinol
  • Resorcinol
    fluoro

Volume and Collective Indexes: General Subject Index

• The General Subject Index uses standard subject headings in order to better bring related documents together (collation).
• The standard headings list does get modified and expanded to reflect new areas of research. Major changes are usually done at the beginning of a Collective Index period. Sometimes the changes are minor, sometimes drastic.
• Prior to 1997, headings were chosen so as to draw related topics into physical proximity in the printed volumes, with electronic searching treated as a secondary aspect of CA. Starting in 1997, headings have been changed to be more like natural language for easier electronic searching, with the print version treated as a secondary aspect of CA.
• For examples of the 1997 changes see the CAS General Subject Vocabulary Helper at http://www.cas.org/vocabulary/
• Broadly speaking, the General Subject Index includes:
  • classes of chemical substances
  • physical and chemical phenomena
  • types of reactions
  • chemical technology
  • industrial processes and equipment
  • scientific names for living organisms
  • biological and medical terminology
• For extensive subjects, qualifiers are added as part of the main subject heading, such as
  • Blood, analysis
• Classes of substances may also have derivative categories, such as
  • Carboxylic acids, esters
  • Sulfonic acids, uses and miscellaneous
• Note: the following lists of categories apply to pre-1997 indexes. Some are undergoing dramatic changes.
• Substance Categories
  • For ketones, aldehydes
    — acetals, hydrazones, mercaptals, oximes
  • For acids
    — anhydrides, anhydrosulfides, esters, lactones
  • For alcohols
    — ethers
  • For amines
    — oxides
  • General: compounds, derivatives, polymers
• Heading Qualifiers
  • For substances and classes of substances
    • analysis
    • biological studies
    • occurrence
    • preparations
    • properties
    • reactions
    • uses and miscellaneous
  • In the electronic versions of the file, these have evolved into role indicators.
  • For organs and tissues
    • composition
    • disease or disorder
    • metabolism
    • neoplasm
    • toxic chemical or physical damage
  • In post-1997 subject headings, the disease and neoplasm headings have been combined with their respective organ or tissue to form separate primary headings.
  • For alloys
    • base — applied to the largest single constituent of the alloy.
    • non-base — applied to other constituents of the alloy.

CA Index Guide

• The Index Guide is the key printed tool for identifying the correct subject heading for any topic in Chemical Abstracts
• Each Index Guide lists the approved headings in use for its period of coverage.
• An IG is published at the beginning of each Collective Index period, with updates every 18 months until the final comes with the Collective Index itself.
• Contents of the Index Guide
  • An alphabetical listing of the approved subject headings, with cross-references to related headings and descriptive notes.
  • Many common terms not used as headings are listed, with See references to the correct heading.
  • Many common and/or trade names for chemical substances are listed, giving the correct CA systematic name (and Registry Number!)
  • There are also appendices on the organization and use of the subject indexes; how CA indexers select headings; CA chemical nomenclature; and a hierarchical list of the headings.
• Whenever you are doing a subject search, in print or online, it’s a good idea to check the Index Guide!! And be sure to check the correct Index Guide for the years you are searching!

The Rule of Specificity

• Usually, CA indexers will assign the most specific subject heading that applies to the document.
• For example, if a document deals with the synthesis of a specific ester, the indexer will assign that substance to the index, not the general term “Esters”.
• In pre-1997 indexes, cancer of the lungs will appear as Lung, neoplasm not Lung, disease.
• From 1997 to the present, the general term in Lung tumors with more specific terms for specific types, e.g. Lung adrenocarcinomas.

This page created by Chuck Huber (huber@library.ucsb.edu).

Grace Baysinger, Head Librarian and Bibliographer
Swain Chemistry and Chemical Engineering Library, Stanford University Libraries
graceb@stanford.edu