Charles, Jacques Alexandre César

[shah®l] (1746–1823) French physicist: established temperature–volume relationship for gases.

Originally a clerk in the civil service, an interest in ballooning and the physics of gases together with a flare for public lecturing brought Charles fame, and ultimately a professorship of physics in Paris.

In 1783, together with his brother Robert, Charles made the first manned ascent in a hydrogen balloon, a feat which brought him considerable public acclaim. On a later flight he was to reach an altitude of 3000 m. His interest in gases subsequently led him to formulate Charles’s Law in 1787, that the volume of a given amount of gas at constant pressure increases at a constant rate with rise in temperature. Further experimental work by confirmed the relationship, which holds best at low pressures and high temperatures (ie it applies to ideal gases). Incidentally,had also discovered the relationship almost a century before but, failing to publicize the fact, did not receive the credit for it.