Benoît Paul Émile Clapeyron

Benoît Paul Émile Clapeyron (; 26 January 1799 – 28 January 1864) was a French engineer and physicist, one of the founders of thermodynamics. He is known for developing the ideal gas law.

Life Born in Paris, Clapeyron studied at the École polytechnique, graduating in 1818. He also studied at École des mines. In 1820 he and Gabriel Lamé went to Saint Petersburg to teach and work at the school of public works there. He returned to Paris only after the Revolution of July 1830, supervising the construction of the first railway lines connecting Paris to Versailles and Paris to Saint-Germain. Clapeyron took his steam engine designs to England in 1836 to find a manufacturer and engaged Sharp, Roberts and Co.

In 1842 Clapeyron published his findings on the "optimal position for the piston at which the various valves should be opened or closed." In 1843, Clapeyron further developed the idea of a reversible process, already suggested by Carnot and made a definitive statement of Carnot's principle, what is now known as the second law of thermodynamics.

These foundations enabled him to make substantive extensions of Clausius' work, including the formula, now known as the Clausius–Clapeyron relation, which characterises the phase transition between two phases of matter. He further considered questions of phase transitions in what later became known as Stefan problems.

Clapeyron also worked on the characterisation of perfect gases, the equilibrium of homogeneous solids, and calculations of the statics of continuous beams, notably the theorem of three moments (Clapeyron's theorem).

Honors Member of the Académie des Sciences, (1858). The Rue Clapeyron in Paris' 8th arrondissement (here) is named for him. His name is one of the 72 names inscribed on the Eiffel Tower.

Publications

(source: The Internet Archive)