He gained his secondary education in Auxerre and Rouen before entering the École Polytechnique, Paris in 1801. He began studying medicine, but gave this up to concentrate on science, working under the direction of Thénard. Dulong succeeded Alexis Thérèse Petit as professor of physics, from 1820 to 1829, then was directeur des études until his death.
Dulong also discovered the dangerously sensitive nitrogen trichloride in 1812, losing two fingers and an eye in the process.1
In 1819 Dulong collaborated with Petit to show that the mass heat capacity of metallicelements are inversely proportional to their atomic masses, this being now known as the Dulong-Petit law.2 Dulong also worked on the elasticity of steam, on the measurement of temperatures, and on the behavior of elastic fluids. He made the first precise comparison of the mercury- and air-temperature scales. At the time of his death, he was working on the development of precise methods in calorimetry.
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