What Is a CAS Number in MSDS?

Material safety data sheets (MSDS) are used in the workplace to provide essential information on the safe use and disposal of chemicals and mixtures. Typically, standard MSDS contain 16 sections in which vital information on a product’s identity, hazards and properties are described.

Chemical Identity

• In order to communicate about chemicals in a standardized way, much of the world uses a standardized numerical identifiers called CAS registry numbers (RNs), instead of chemical names.

CAS

• CAS, or Chemical Abstracts Service, a division of the American Chemical Society, assigns unique CAS numbers to individual chemicals. Generally, there is one specific CAS number for each chemical.

Format

• CAS RNs always take the form of a code segmented into three sections separated by dashes. The first section contains at least two digits, the second section always contains two digits and the third section always contains one digit. Generally, a CAS RN would look like: [string of digits]-XX-X. For example, the CAS number for benzene is 71-43-2 and the CAS number for copper is 7440-50-8.

Reasoning

• Because of the extraordinary number of chemical name synonyms and the number of languages users of chemicals speak, using numbers to identify chemicals makes communicating vital information more efficient. Additionally, databases that contain information on chemicals are better able to handle searches based on codes than multiple chemical name synonyms.

Where to Find a CAS Number on the MSDS

• Around the world, the formats used to write MSDS vary significantly. Typically, you will find the CAS RNs for chemicals in a product on the first page of an MSDS in either Sections 2 or 3.