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CAS Registry Number

Last updated: March 6, 2016

What Does CAS Registry Number Mean?

CAS (Chemical Abstracts Service) registry numbers are an authenticated collection of more than 100 million organic and inorganic disclosed chemical substances and more than 66 million sequences. Each CAS registry number is a short sequence of numbers separated by hyphens.


Corrosionpedia Explains CAS Registry Number

The CAS registry number system was developed to overcome the limitations of other chemical naming convention systems such as systems derived from the molecular structure of the chemical substances (e.g., IUPAC nomenclature).

The digits before the first hyphen represent the CAS (Chemical Abstracts Service) and remaining digits denote the registry number. For example, in case of aspirin, the CAS number is 50-78-2. Here 50 represents CAS and 78-2 represents registry number.

Some example chemical substance CAS registry numbers are:

  • Aspirin: 50-78-2
  • Water: 7732-18-5
  • C-glucose: 50-99-7
  • Sodium chloride: 7647-14-5
  • Formaldehyde: 50-00-0

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