Julius Robert von Mayer

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Julius Robert von Mayer.

Julius Robert von Mayer (November 25, 1814 – March 20, 1878) was a German physician and 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 priority for the discovery of the mechanical equivalent of heat was long attributed to James Joule in the following year.

1 Life
2 Development of ideas
3 Later life
4 Honours
5 Notes
6 Bibliography
7 External links

[edit] Life

Mayer grew up in Heilbronn, the son of a pharmacist. After completing his Abitur, he studied medicine at the University of Tübingen, where he was a member of the Corps Guestphalia, a German Student Corps. In 1838 he attained his doctorate as well as passing the Staatsexamen. After a stay in Paris (1839/40) he left as a ship's physician on a Dutch three-mast sailing ship for a journey to Jakarta.

Although he had hardly been interested up to the start of this journey in physical phenomena, his observation that storm-whipped waves are warmer than the calm sea sparked deep thinking about the laws of nature, in particular about the physical phenomenon of warmth and the question: whether the directly developed heat alone or whether the sum of the amounts of heat developed in direct and indirect ways contributes to the temperature. After his return in February 1841 Mayer dedicated all its effors to the solution of this problem.

In 1841 he settled in Heilbronn and married.

[edit] Development of ideas

To understand the significance of Mayer's work in the context of the development of thermodynamics, see Thermodynamics timeline Edit

He sent a paper to Johann Christian Poggendorff's Annalen der Physik in which he postulated a Erhaltungssatz der Kraft, by which he meant a conservation law energy. However, owing to Mayer's lack of advanced training in physics, it contained some fundamental mistakes and was not published. Mayer continued to pursue the idea steadfastly and argued with the Tübingen physics professor Johann Gottlieb Nörremberg, who rejected his hypothesis. Nörremberg however, gave a number of valuable suggestions on how it could be examined experimentally. If kinetic energy transforms into heat energy, water must be warmed up by vibrating.

Mayer not only performed this demonstration, but determined also the quantitative factor of the transformation, the mechanical equivalent of heat. The result of his investigations was published 1842 in the May edition of Justus von Liebig's Annalen der Chemie und Pharmacie (Annalen der Chemie und Pharmacie, 43, 233 (1842)) . In his booklet Die organische Bewegung im Zusammenhang mit dem Stoffwechsel (The Organic Movement in Connection with the Metabolism (1845) he could specified the numerical value of the mechanical equivalent of heat: at first as 365 kgf·m/kcal^[1], later as 425 kgf·m/kcal; the modern values are 4.184 kJ/kcal (426.6 kgf·m/kcal) for the thermochemical calorie and 4.1868 kJ/kcal (426.9 kgf·m/kcal) for the international steam table calorie.

This relation implies that work and heat equivalent to each other and are different forms of energy which can be transformed. This law is called the first law of the caloric theory and led to the formulation of the general principle of conservation of energy, definitively stated by Hermann von Helmholtz in 1847.

Mayer derived what is now known as Mayers' relation:

C_p - C_v = R

- where C_p is the specific heat of a gas at constant pressure, C_v is specific heat of a gas at constant volume and R is the gas constant.

[edit] Later life

For dispute over priority with Joule, see main article Mechanical equivalent of heat: Priority.

Mayer was aware of the importance of his discovery, but his inability to express himself scientifically led to degrading speculation and resistance from the scientific establishment. Contemporary physicists rejected his principle of conservation of energy. Even acclaimed physicists Hermann von Helmholtz and James Prescott Joule viewed his ideas with hostility. The former doubted Mayer's qualifications in physical questions, and a bitter dispute over priority developed with the latter.

In 1848 two of his children died rapidly in succession, and Mayer's mental health deteriorated. He attempted suicide on May 18, 1850 and was committed to a mental institution. After he was released, he was a broken man and only timidly re-entered public life in 1860. However, in the meantime, his scientific fame had grown and he received a late appreciation of his achievement, although perhaps at a stage where he was no longer able to enjoy it.

He continuted to work vigorously as a physician until his death.

[edit] Honours

The Robert-Mayer-Gymnasium and the Robert-Mayer-Volks- und Schulsternwarte in Heilbronn bear his name.

[edit] Notes

↑ The physical unit kgf·m/kcal measures mechanical energy, in kgf·m, against heat energy, in kcal. The mechanical energy is measured on the basis of raising a mass of m kg to a height of h m against Earth's gravity. This is equivalent to an energy of mgh joules, where g is the standard acceleration due to gravity. Thus, 1 kgf·m/kcal = 9.80665 J/kcal.