Due to his family he early came in contact with medicine and the natural sciences, in 1804 he attended the chemical lectures of his father.

Supported by Kielmeyer, Gmelin moved to the University of Göttingen in 1805 and later he worked as assistant in the laboratory of Friedrich Stromeyer, by whom he successfully passed his exams in 1809.

Focus of his research was the Black pigment of oxen and calves eyes, outcome of this work was also the subject of Gmelins dissertation.

Together they had three daughters and one son, including Auguste, the future wife of the physician Theodor von Dusch.

When Friedrich Wöhler worked on complex cyanogen compounds in 1822, Gmelin assisted him and discovered the Red prussiate.

In this edition Gmelin included atomic theory and devoted much more space to the increasingly important organic chemistry.

Gmelin's first physiological work was his dissertation on the black pigment of oxen's and calves' eyes, whose coloring principle he tried to fathom.

Furthermore, Gmelin and Tiedemann delivered a new, more refined view of the absorption of nutrients through the gastrointestinal tract; they were the founders of modern physiology.

Leopold Gmelin's mineral system was taken largely critical among experts, but the basic idea of an order based on the chemical composition proved to be useful.

The manual, even during his lifetime his most important work, was initially intended to be a textbook, which should unite the whole chemical knowledge at that time.

Due to the enormous increase in knowledge and the associated development of the handbook into a reference book, Gmelin published a compact textbook of chemistry in 1844.