Jean Pierre Chardenon

Jean Pierre Chardenon (* 1714 in Dijon ; † March 16, 1769 ibid) was a French doctor and chemist.

Chardenon was baptized on July 22, 1714. He first became a surgeon in Paris, but due to poor health, he became a doctor instead and practiced in Dijon.

Chardenon was Agrégé at the College of Medicine in Dijon and in 1744 became an associate member and 1747 pensioner of the Academy of Sciences and Arts in Dijon, founded in 1740, and one of the academy's secretaries from 1752 to 1762. Before attending the academy, he gave lectures on medicine and surgery as well as chemistry related to medical issues.

He wrote a formulation of the law of conservation of mass (1763/64). This happened during several meetings of the Academy of Dijon in 1763 and 1764 (published in 1769). His lecture was about the calcination of metals and the weight gain that can be observed in the process, which, in his own estimation, would be one of the most interesting problems in physics. The process would have been proven by many experiments and recognized by all physicists. He had raised the question himself and in 1762 left a sealed envelope with his solution. Chardenon was a supporter of the phlogiston theory , but in a special form. The phlogiston corresponds to fire particles and is lighter than air and provides buoyancy (he compared this explicitly with cork particles, which would give buoyancy to a fishing net and prevent it from sinking). If it is removed from the metal, as in calcination, it becomes heavier. In doing so, he contradicted other phlogiston supporters such as Laurent Beraut (dissertation for the Academy in Bordeaux in 1747), who attributed the increase in weight to the uptake of particles from the air, but not from fire particles themselves, as Robert Boyle said, fire would be too light for that. This only brings about the union with the metal. Chardenon planned to confirm this through experiments. If his theory were correct, the increase in weight would correspond to the amount of phlogiston, which in turn could be determined by the amount of coal during combustion. He died before he could carry out the experiments. His colleague at the Guyton de Morveau Academy continued the research, and he also received much more attention than Chardenon.

Chardenon also studied the nature of oil, which some of his contemporaries believed to be a principle of nature, as it would occur in all three realms of nature. Chardenon showed, however, that by heating it can be broken down into acid, water, phlogiston (combustion residues) and earth. Since these substances would not reconnect by themselves (or could be connected by affinity ), Chardenon suspected that this would require an action by the living part of nature (animals, plants). According to Chardenon, mineral oils are created by the decay of plant material in the depths of the earth.

In 1761 he investigated the question of how mercury acts as a poison. According to him, due to its high density, mercury interacted with body substances (since - according to Chardenon - it has been proven in physics that the effect of bodies on one another would depend on their mass).

literature

• William Arthur Smeaton : Chardenon, Jean Pierre , in Dictionary of Scientific Biography
• James Riddick Partington : A history of chemistry , Macmillan 1962, Vol. 3, pp. 610f

Fonts

During his lifetime, only Extrait de la séance publique de l'Académie de Dijon, le 9 décembre 1764 , in: Mercure de France, July 1765, part 2, pp. 127-134 and another criticism of Beraut Lettre de M appeared on his theory of combustion Chardenon sur l'augmentation de poids des matières calcinées , Journal des Sçavans 1768, pp. 648-658. The complete article appeared posthumously : Mémoire sur l'augmentation de poids des matières calcinées , Mémoires de l'Académie de Dijon, Volume 1, 1769, pp. 303-320

References and comments

1. ↑ He distinguished two types of severity, absolute and specific. The absolute gravity of bodies can only be increased by adding matter.