CAS REGISTRY®, the CAS substance collection, is the premier source relied upon by scientists and regulators worldwide for accurate information on chemical substances.

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CAS Registry Numbers (CAS RN) are simple and regular, convenient for database searches. They offer a reliable, common and international link to every specific substance across the various …

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Search and explore chemical information in the world's largest free chemistry database. Search chemicals by name, molecular formula, structure, and other identifiers. Find chemical and physical …

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Mar 9, 2026 · CAS numbers give every chemical substance a unique identifier. Here’s how they work and why they matter in labs, databases, and everyday products.

CAS is a leader in scientific information solutions and a division of the American Chemical Society. For over 100 years, scientists, patent professionals, and business leaders have relied on...