High Quality Content by WIKIPEDIA articles! The Merck Index is an encyclopedia of chemicals, drugs and biologicals with over 10,000 monographs on single substances or groups of related compounds. It also includes an appendix with monographs on organic name reactions. It is published by the United States pharmaceutical company Merck Co. The Merck Index is also available by subscription in an electronic searchable form, commonly carried by research libraries, as well as in a web-accessible form.