What is CAS number?
A CAS number, known as a Chemical Abstracts Service Number (CAS), is a unique identification number assigned to a chemical substance by the U.S. Chemical Abstracts Service (CAS). Each known chemical substance, including elements, compounds, mixtures, and biomolecules, is assigned a specific CAS number. This numbering system is widely used in the chemical, pharmaceutical, and materials science industries and is intended to provide a globally consistent standard for the identification of chemical substances.
Structure and Meaning of CAS Number
The CAS number consists of three numbers in the format “XXX-XX-X”. The first three digits are the serial number, the middle two digits are used for checking, and the last digit is the check digit. This numbering system is designed to ensure that each chemical substance has a unique identity, avoiding confusion due to different nomenclature or language. For example, the CAS number for water is 7732-18-5, and reference to this number points to the same chemical substance regardless of country or industry.
Importance of CAS numbers and application areas
The importance of CAS number is mainly reflected in the following aspects:

Global chemical substance identification: CAS number provides a globally unique identity for each chemical substance. Whether in scientific literature, patent applications, product labelling or safety data sheets, the CAS number serves as a uniform standard and ensures consistent information.

Data Management and Retrieval: Due to the wide variety of chemical substances and their complex nomenclature, CAS numbers make the management and retrieval of chemical databases more efficient. Researchers, chemical companies and government agencies can quickly and accurately access information about chemical substances through CAS numbers.

Regulatory compliance and safety management: In chemical management, CAS numbers are an important tool to ensure regulatory compliance. Many national and regional chemical regulations, such as Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) and Toxic Substances Control Act (TSCA), require CAS numbers to ensure the legality and safety of chemical substances.

How do I find and use a CAS number?
CAS numbers are usually found through specialised databases or chemical literature, such as the CAS Registry, PubChem, ChemSpider, etc. When using a CAS number, it is important to ensure that the number entered is accurate, as even a single digit error can result in a completely different chemical substance being retrieved. CAS numbers are commonly used in chemical manufacturing and research processes for procurement, quality control, and the preparation and management of safety data sheets.
Summary
As a globally used chemical substance identification system, CAS number greatly improves the efficiency and accuracy of chemical information retrieval. CAS numbers play an irreplaceable role in the chemical industry, whether in research and production, or in regulatory compliance and safety management. Therefore, understanding and correctly using CAS numbers is crucial for chemical industry practitioners.