Chemical Abstracts Service (CAS)
Definition and meaning of Chemical Abstracts Service (CAS) in chemistry.
The Chemical Abstracts Service is a division of the American Chemical Society. This group keeps a massive catalog of every chemical ever reported in scientific literature. They assign a unique identification number to every single chemical substance known to exist.
In more detail
Naming chemicals can get very messy and confusing for students and professional scientists alike. A single chemical molecule might have a long scientific name and a shorter common name. Different countries and different companies might call the exact same substance by different names.
A CAS Registry Number solves this problem by giving every chemical a unique fingerprint. The number itself does not tell you anything about the actual chemistry or structure. It is simply a random string of up to ten digits separated by hyphens.
The very last digit serves as a mathematical check to prevent accidental typing errors. This organization started tracking and registering chemical substances way back in the year 1957. Today, their massive computer database holds well over two hundred million different chemical compounds.
When a scientist discovers a brand new molecule, they must submit it for registration. The service checks the chemical structure and then assigns it a permanent serial number. You will find these helpful identification numbers printed on every chemical safety data sheet.
Government regulators rely on these exact numbers to track hazardous waste and environmental pollution. Schools use these same numbers to organize all the bottles in their chemistry stockrooms.
Key facts
| Field | General Chemistry |
|---|---|
| Parent Organization | American Chemical Society |
| Year Started | 1957 |
| Number Format | Up to ten digits separated by hyphens |
| Database Size | Over 200 million recorded chemical compounds |
| Primary Purpose | Provides a unique identifier for every chemical |
Everyone knows the chemical name for the water we drink is simply dihydrogen monoxide. However, in the official global database, water is always registered as CAS number 7732-18-5. Meanwhile, the ordinary table salt you sprinkle on food goes by CAS number 7647-14-5. If you type these exact numbers into a supply catalog, you get the right chemical. There is absolutely zero chance of mixing them up with another similar chemical substance.
Frequently asked questions
Does a CAS number tell you about a substance's chemical structure?
No, the number itself carries absolutely zero meaning about the chemistry or atomic structure. It is simply a unique lookup key that acts like a social security number.
Is a CAS Registry Number the same thing as an IUPAC name?
No, a CAS number is a numeric code assigned to a chemical for tracking. An IUPAC name uses strict vocabulary rules to describe the actual shape of molecules.
Do mixtures of chemicals get their own unique CAS numbers?
Many common mixtures and metal alloys do have their own specific assigned CAS numbers. However, scientists mostly use these numbers to track single pure chemical elements and compounds.