The CAS RegistrySM

The mechanization of information yielded CAS' most significant and far-reaching innovation: The Chemical Registry System. G. Malcolm Dyson, hired by Dale Baker in 1959, first suggested the idea of a registry in the late 1950s. CAS needed an alternative to chemical nomenclature as a basis for this registry. With the increasing complexity and sheer numbers of substances appearing in the literature, the variability in nomenclature rules did not provide unique and unambiguous chemical names.

But chemists have an advantage over many other scientists in being able to communicate by referring to chemical compounds through unambiguous and universally understood structural diagrams. These diagrams indicate a compound's chemical atoms, the bonds that connect them, and even the spatial arrangement of the atoms. But there was no good way to catalogue these structures that enabled easy retrieval. At CAS, every time a chemical compound was indexed it was copied by hand and then given a name, which may or may not have agreed with the name given it by its presumed discoverer. Was the compound really new? Had it been reported in the literature? Indexed by CA? The rapid increase in the number of named structures led to much confusion; some compounds were named over and over.

Clearly, CAS needed a system that recognized previously named structures and allowed for easy retrieval by CAS staff. In the early 1960s a solution was found when Harry Morgan of CAS developed a solution using an algorithm that generates a unique and unambiguous two-dimensional record of a substance's structure. The record can be read by a computer and was so simple that staff with little special training could employ it. The algorithm became the basis of the CAS Chemical Registry System.

In late 1964 an experimental Chemical Registry System went into operation supporting the new publication Chemical-Biological Activities. By early 1965, the Registry, no longer experimental, began to include all chemical substances indexed in CA, with their structures and names recorded in computer-readable files. Every substance was given a permanent, unambiguous, and unique identifying number, the CAS Registry Number®. For example, a certain statin drug has a systematic chemical name of about 70 characters and is associated with several different tradenames. But it is concisely identified by the CAS Registry Number 79902-63-9. Today scientists and researchers around the world rely upon the CAS Registry Number as the globally accepted standard for defining and describing a chemical substance.

Though the system would go through several iterations over the years, it quickly became an integral part of CA's indexing procedures. More advanced versions were soon added which refined and improved nomenclature and the ability to recreate structure diagrams algorithmically. It took only ten years for the Registry to record three million unique structures. But the Registry's virtue is not limited to size or number; its success has eliminated the vagaries of chemical nomenclature since every unique substance gets a unique CAS Registry Number.


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