The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals is a comprehensive reference work that has served as a cornerstone for scientists, healthcare professionals, and researchers since its inception in 1889. Now in its 15th edition, published by the Royal Society of Chemistry in 2013, this volume encompasses over 10,000 monographs detailing chemical substances of significance in various fields, including pharmaceuticals, agriculture, and environmental science. Each entry provides critical information such as chemical names, CAS Registry Numbers, molecular formulas, molecular weights, structural formulas, physical properties, and therapeutic classifications.

The 15th edition introduces more than 500 new monographs and updates over 3,500 existing entries, reflecting the latest IUPAC standards and recalculating molecular weights accordingly. Supplemental tables have been expanded to include nonproprietary pharmaceutical name stems, vaccines, medicinal radioisotopes, and conversion factors. Additionally, the edition features over 500 named organic reactions, enhancing its utility for researchers and educators. A complimentary one-year subscription to The Merck Index Online is included with the purchase, offering access to a fully searchable database of over 11,500 monographs, including historic entries not available in the print edition.

The Merck Index is organized alphabetically and includes cross-references by CAS Registry Number, chemical formula, and therapeutic activity, facilitating efficient information retrieval. Its monographs are concise yet comprehensive, often including references to scientific literature and patents, making it an indispensable tool for professionals in chemistry, pharmacology, toxicology, and related disciplines. The inclusion of a glossary and various indexes further enhances its accessibility and practical application .

The Merck Index stands as a venerable and invaluable resource, embodying a tradition of scientific excellence and reliability. Its meticulous compilation and regular updates ensure that it remains a vital tool for those seeking authoritative information on chemicals, drugs, and biological substances. Whether in print or online, it continues to support the advancement of research and education across multiple scientific domains.