CAS registry number

CAS Registry Number is a unique numerical identifier assigned to every chemical substance that has been described in the literature. It is used to provide a unique, unambiguous identifier for chemical substances and is managed by the Chemical Abstracts Service (CAS), a division of the American Chemical Society.

Overview

A CAS Registry Number, often abbreviated as CAS RN or CAS Number, is a unique numeric identifier assigned to a chemical substance by the Chemical Abstracts Service. The number itself is a sequence of digits divided by hyphens into three parts. The rightmost segment consists of a single check digit, the middle segment consists of two to seven digits, and the leftmost segment includes up to two or three digits. This format helps ensure each chemical substance is associated with a unique number.

Purpose and Use

CAS Numbers are used worldwide by chemists, researchers, regulatory bodies, and information systems to identify substances without ambiguity. Unlike chemical names which can vary according to language and naming standards, a CAS Number is a consistent identifier that is recognized globally. It is used in various databases, regulatory documents, and chemical inventories to link information related to specific substances.

Assignment Process

The assignment of a CAS Number is a systematic process carried out by the Chemical Abstracts Service. When a new substance is reported in the scientific literature, CAS adds the substance to its database and assigns it a new CAS Number. The process involves analyzing the chemical structure and ensuring that the new substance is not already present in the database.

Applications

CAS Numbers are essential in many fields including chemistry, pharmacology, environmental science, and regulatory affairs. They are used in:

• Scientific research papers
• Chemical catalogs and databases
• Material safety data sheets (MSDS)
• Regulatory and compliance documents

Limitations

While CAS Numbers are invaluable for identifying chemical substances, they do not convey any chemical information such as structure or molecular formula. Additionally, some substances, particularly polymers and biological sequences, may not be assigned CAS Numbers due to their complex or variable nature.

See Also

• Chemical Abstracts Service
• IUPAC nomenclature
• Molecular formula
• Chemical structure