The Merck Index is an encyclopedia of chemicals, drugs and biologicals with over 10,000 monographs on single substances or groups of related compounds<ref name=db-intro /> published online by the Royal Society of Chemistry.<ref name="acscinf.org">{{#invoke:citation/CS1|citation
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The NFL edition of the Merck's Index was published in 1889 by the German chemical company Emanuel Merck and was primarily used as a sales catalog for Merck's growing list of chemicals it sold.<ref name="acscinf.org"/> The American subsidiary was established two years later and continued to publish it. During World War I the US government seized Merck's US operations Merck & Co., forming a separate American company that continued to publish the Merck Index.
In 2012 the Merck Index was licensed to the Royal Society of Chemistry.<ref name= acq>Template:Cite press release</ref> An online version of The Merck Index, including historic records and new updates not in the print edition,<ref name=db-intro>{{#invoke:citation/CS1|citation
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The 15th edition was published in April 2013.
Monographs in The Merck Index typically contain:<ref name=db-intro />
