Julius Robert von Mayer (November 25, 1814 – March 20, 1878) was a German physicist. He described the vital chemical process now referred to as oxidation as the primary source of energy for any living creature in 1842. His achievements were overlooked and the credit was given to James Joule 5 years later.
He proved what is now known as Mayers' Relation
Cp-Cv=R
Where Cp is specific heat of a gas at constant pressure and Cv is specific heat of a gas at constant volume and R is the gas constant.