CAS Registry Numbers (CAS RN) are used to locate information about a chemical compound quickly and accurately. CAS Registry Numbers were developed in the 1960s by the Chemical Abstracts Service, a division of the American Chemical Society.
Every chemical compound has its own CAS Registry Number, and there are thus millions and millions of CAS Registry Numbers. 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 Registry Number always ends with -xx-x. The Registry Number is created by an automatic algorithm.
Many of the scientific databases allow searching by CAS Registry Number. Once you determine the correct Registry Number for a compound, always use that when searching.
When reading older literature, you will not find CAS Registry Numbers mentioned. However, SciFinder-n has done some retrospective indexing, and attached Registry Numbers to ALL preparations found in their database and continues to add additional ones to old records.
CAS Registry Numbers are occasionally deleted or replaced. In the SciFinder-n database, all Registry Numbers assigned to a compound are linked together, so one search by Registry Number will provide all articles on that chemical.
