> For the complete documentation index, see [llms.txt](https://docs.rplpeptides.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rplpeptides.com/docs/glossary/chemical-terms/cas-number.md). # CAS Number ## Definition A CAS (Chemical Abstracts Service) Registry Number is a unique numerical identifier assigned to every chemical substance described in the scientific literature, including peptides. ## Overview CAS numbers provide a unique, unambiguous identifier for chemical substances, avoiding confusion from different naming conventions or synonyms. They are widely used in procurement, regulatory documentation, and database searches. ## Technical Explanation **Format:** A CAS number has three parts separated by hyphens: XXXXXX-YY-Z * The first part contains up to 7 digits * The second part has 2 digits * The third digit is a check digit for validation **For Peptides:** * Not all synthetic peptides have CAS numbers (some are novel or proprietary) * Peptide CAS numbers identify the specific sequence and modification state * Different salt forms of the same peptide may have different CAS numbers **Validation:** CAS numbers can be validated using the check digit algorithm. Verified CAS numbers are essential for proper chemical inventory management. ## Importance in Peptide Documentation CAS numbers are included in product documentation (TDS, SDS) to provide an unambiguous reference for chemical identification. They facilitate ordering, inventory tracking, and regulatory compliance. ## Related Terms * [Molecular Formula](/docs/glossary/chemical-terms/molecular-formula.md) * [Technical Data Sheet](/docs/glossary/documentation-terms/technical-data-sheet.md) ## Frequently Asked Questions **Q: Do all research peptides have CAS numbers?** A: Most well-established peptides have CAS numbers. Novel peptides or newly developed analogs may not yet have assigned CAS numbers. **Q: Can two peptides share the same CAS number?** A: No. Each distinct chemical substance has a unique CAS number. Different salt forms or modifications of the same base peptide receive different CAS numbers. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.rplpeptides.com/docs/glossary/chemical-terms/cas-number.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.