C
hemical Abstracts Service (CAS) Registry Numbers (RNs) are unique numbers
that are assigned to chemical substances by the CAS Registry Service. RNs appear in
the BIOSIS Previews/RN file in the RN data element. Over 106,000 unique RNs are
available from 1969 to the present, for a total of over 4 million RNs as of June 1994.
In addition to Registry Numbers, the corresponding chemical names also appear in
the RN data element, following each RN.
To balance the need for current data with the need for comprehensive RN indexing,
a two-step process is used to assign RNs to chemical terms. First, for each of the four
updates per month, a computer algorithm is used to assign RNs to chemical terms
occurring in the Title and Supplementary Terms data elements. Any chemical terms
that are not matched using the algorithm are sent to the CAS Registry Service for
RN assignment. All additional RNs identified by the Registry Service are added once
each month.
Some chemical names are not precise enough to generate a specific RN assignment.
To alert searchers to these possible ambiguities, three RN suffixes are used. The
Q suffix, indicating questionable assignment, signals that a chemical name matched
more than one Registry Number. For example, if a reference discusses copper chloride,
the chemical may be either copper(I) chloride or copper(II) chloride. The RNs for both
substances would be listed in this case and each RN would be indexed twice, both with
and without the Q suffix.
The D suffix is used when the chemical compound being discussed is a derivative
of a registered chemical or class of chemicals (e.g., carboxy-substituted dibenzofurans).
Chemicals with the D suffix are not posted twice, but truncation will retrieve RNs
appended with the D suffix. Some RNs have a DQ suffix which signals a combination
of these two cases.
To retrieve comprehensive chemical information from BIOSIS Previews/RN,
including chemical information appearing only in the abstract, search chemical
names and their synonyms along with the RN. One convenient way of finding RNs
and synonyms for chemicals is to use the Registry File. Each entry in the Registry File
contains a chemical name, its structure when available, its synonyms and the RN.
Use the "select chem" command to transfer chemical names and/or RNs from the
Registry File into BIOSIS Previews/RN.
To retrieve terms from the abstract, use the "select chem" command. Go into the
Registry File and select an RN or common name. Enter "select chem" which will
retrieve E numbers equal to the number of names assigned to each substance. Transfer
to the BIOSIS Previews/RN file. Search the E number range. The resulting L# set will
include all references for the chemical names appearing in the Title, Supplementary
Terms and Abstract fields.
H o w t o S e a r c h U s i n g R e g i s t r y N u m b e r s
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H o w t o S e a r c h U s i n g
R e g i s t r y N u m b e r s
