Chemistry research relies heavily on serial literature. Indeed, the use of serials rather than monographs is probably greater in chemistry than in other sciences. Therefore checking a standard list of serial titles is the most effective way to assess the extent and strength of a library’s chemistry collection. One such listing is the List of 1000 Journals Most Frequently Cited by Chemical Abstracts. Another is the Science Citation Index: Annual Source Publications — Journals Arranged by Subject Category. While the latter has the advantage of listing chemistry journals under broad subjects, it includes only the major titles in the field. In the following supplemental guidelines, each succeeding level is presumed to be inclusive of those that precede it. In assigning values for ECS and CCI, it is important to bear these points in mind:

1. These values describe collections or collecting policies absolutely, not relatively. They assume therefore a national perspective and a broad cognizance of all facets of collecting.
2. When the value describes existing collection strength, it should relate to national shelflist measurement, reflecting what is actually on the shelves.
3. When the value describes current collecting intensity, it represents actual collecting practices, and not policy, if that policy is being imperfectly observed.
4. All applicable formats should be taken into account when determining subject values. This will mean considering such items as journals, audiovisual and other nonprint materials, technical reports, and so on. Particular strengths, weaknesses, special collections, or other outstanding or unusual factors should be indicated in the "Comments" section.

To aid bibliographers in establishing the collection levels for chemistry, the level codes have been expanded as follows:

0. Out of scope: The library does not collect in this area.
1. Minimal level: A subject area in which few selections are made beyond very basic works.
2. Basic information level: A collection of up-to-date general materials that serve to introduce and define a subject and to indicate the varieties of information available elsewhere. It may include dictionaries, encyclopedias, selected editions of important works, historical surveys, bibliographies, access to appropriate bibliographic data bases, handbooks, a few major periodicals, in the minimum number that will serve the purpose. A basic information collection is not sufficiently intensive to support any advanced undergraduate or graduate courses or independent study in the subject area.
3. Instructional support level: A collection that is adequate to support undergraduate and MOST graduate instruction, or sustained independent study; that is, adequate to maintain knowledge of a subject required for limited or generalized purposes, of less than research intensity. It includes a limited selection of monographs, and general texts primarily in English. It includes the major indexing and abstracting services in the field, access to appropriate non-bibliographic data bases, and a wide range of basic serials, including 10 to 15 percent of the titles pertinent to the subject area being described that are listed in the List of 1000 Journals Most Frequently Cited by Chemical Abstracts.
4. Research collection: A collection that includes source material required for dissertations and independent research. It will contain publications, manuscripts, and other materials and data in a variety of forms as appropriate, and may include conference proceedings, professional society publications, research reporting, new findings, scientific experimental results, and other information useful to researchers. Although English materials dominate, the collection includes pertinent material in relevant foreign languages. It also includes the important reference works, a wide selection of specialized monographs, and special collections if appropriate to the field, as well as major indexing and abstracting services in the field. It contains a very extensive collection of serials, including between 60 and 70 percent of the titles pertinent to the subject area being described on the List of 1000 Journals Most Frequently Cited by Chemical Abstracts. Older material is retained for historical research.
5. Comprehensive level: A collection in which a library endeavors, so far as is reasonably possible to acquire all significant works of recorded knowledge (publications, manuscripts, other forms), in all applicable languages, for a necessarily defined and limited field. The level of collecting intensity would maintain a national resource collection in chemical journals, containing close to 90 percent of the titles included on the List of 1000 Journals Most Frequently Cited by Chemical Abstracts. The aim, if not the achievement, is exhaustiveness.