Pierre Louis Dulong

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Pierre Louis Dulong (February 12, 1785 – July 19, 1838) was a French physicist and chemist.

Dulong was born in Rouen, France. He worked on the specific heat capacity and the expansion and refractive indices of gases.

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 direction of Thénard. He succeeded Alexis Thérèse Petit as professor of physics, from 1820 to 1829, then was directeur des études until his death.

In chemistry, he contributed to knowledge on:

• the double decomposition of salts (1811)
• nitrous acid (1815)
• the oxides of phosphorus (1816)
• the oxides of nitrogen
• catalysis by metals (1823, with Thénard)

He discovered the dangerously sensitive nitrogen trichloride in 1812, losing two fingers and an eye in the process.^[1]

In physics, in collaboration with Petit, he showed that the mass heat capacity of metallic elements was inversely proportional to their atomic masses, this being now known as the Dulong-Petit law. He 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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