CAS Registry numbers are used to locate material about a chemical quickly and accurately. CAS Registry numbers were developed in the 1960's by the American Chemical Society.
Every SINGLE chemical has its own CAS Registry number. These are easily recognizable, as the following format is maintained:
xxxxxx-xx-x where each x is a single digit from 0-9.
There may be any number of digits in the first group, but a CAS Registry number always ends with -xx-x. The CAS Registry number is done by an automatic algorithm.
There are millions and millions of CAS Registry numbers.
Many of the scientific databases allow searching by CAS Registry number. Once you determine the correct CAS Registry number for a compound, always use that CAS Registry number when searching.
When reading older literature, you will not find CAS Registry numbers mentioned. However, SciFinder Scholar has done some retrospective indexing, and attached CAS Registry numbers to ALL preparations found in the SFS database and continues to add additional CAS Registry numbers to old records.
CAS Registry numbers can be deleted or replaced. In the SFS database, all registry numbers assigned to a compound are linked together, so one search by registry number will provide all articles on that chemical.
Marion Muskiewicz 12/17/2020