A CAS Registry Number is an identity aid in chemical procurement. Use it alongside the chemical name, physical form, grade and specification of the offered material. It can reduce ambiguity between different names, but it does not replace the rest of the product definition.
What a CAS Registry Number identifies
CAS describes a CAS RN® as a unique numeric identifier assigned to a specific substance. The identifier itself has no inherent chemical meaning. See the CAS REGISTRY® overview for the official explanation and the boundaries of the system.
The last digit is a check digit that can identify many typing errors. A number that passes the check digit is structurally valid, but that calculation does not prove that it belongs to the name, formula or material stated in an offer.
Match the exact form of the substance
Related materials can have different identifiers. Distinguish a free compound from a salt and check whether hydration, stereochemistry, composition or another identity detail matters. A solution may need both the solute identity and concentration.
For mixtures, polymers, natural substances and proprietary formulations, one CAS number may not describe the whole commercial product. Composition, grade, product code and supplier specification can be necessary in addition to constituent identifiers.
Keep identity separate from specification
The same substance can be offered in grades with different impurity limits, physical properties, test methods or packaging. A correct identifier does not establish that the offered batch fits a food, pharmaceutical, cosmetic, electronics or industrial application.
Write the acceptance criteria separately: grade, assay, moisture, impurity limits, particle size, color, applicable tests and any other property that controls suitability.
Cross-check a reference, then check the offer
Recognized databases such as PubChem can help cross-check names, formulas and identifiers. CAS remains the authority for CAS Registry Numbers. A database match supports identity work; supplier specifications, batch documentation and the final quotation define the proposed commercial supply.
Regulatory status is a separate question
The presence of a CAS number does not establish approval, inventory listing, permitted use or compliance in a destination. Those questions depend on the material, use and jurisdiction and should be reviewed against current official sources.
Search and enquire
Use the product search to look up a CAS number or chemical name. On a product page, compare the name, formula and source reference before using the record. If the catalog has no match, include both name and identifier in a sourcing enquiry together with the required grade, quantity and destination.
Scope of this guide
This material supports chemical sourcing preparation. It does not replace current supplier documents, regulatory advice or application-specific technical review.
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