The encyclopedia · R&D & Science · Technical decision · 1956–1965
CAS Registry Numbers gave every chemical one ID that all databases share
Since 1965 CAS has assigned each substance one hyphenated number with a check digit, so synonyms, nomenclatures, and languages all resolve to the same compound.
Chemical Abstracts Service
the move
Chemicals were known by dozens of synonyms, trade names, and systematic names that varied by country and era, so deciding whether a substance was new or previously known was a research bottleneck. Chemical Abstracts Service had to index substances reliably from the literature.
In the 1950s CAS introduced the Chemical Registry System, and it became operational in 1965: each substance receives a unique CAS Registry Number, avoiding the ambiguity of chemical nomenclature. CAS's own history calls the system a boon to chemical research, health and safety information, and communication.
The number is pure identity: sequential, with no encoded chemistry, formatted like 7732-18-5 for water, with a check digit that catches transcription errors. Wikipedia notes that almost all molecule databases allow searching by CAS Registry Number and that it is used as a global standard, with more than 200 million substances registered.
why it works
- A number is shorter and more precise than any name in any language.
- Central assignment guarantees uniqueness and one-to-one substance mapping.
- The check digit lets computers catch transcription errors.
- Neutrality let industry, science, and regulators share the same key.
what transfers
When a field cannot agree on names, separate identity from language: a centrally issued, meaningless number gives every synonym one stable target.
what came after
CAS Registry Numbers became the common language of chemical databases, patents, safety data sheets, and regulations worldwide, with the registry growing by about 15,000 new substances a day.
references
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