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Benoit Paul Émile Clapeyron

**Benoît Paul Émile Clapeyron** (26 February 1799 –
28 January 1864) was a French
engineer and physicist, one of the
founders of thermodynamics.

## Life

Born in Paris, Clapeyron
studied at the École
polytechnique and the École des Mines,
before leaving for Saint Petersburg in 1820 to teach at
the *École des Travaux Publics*. He returned to Paris only
after the Revolution of
July 1830, supervising the construction of the first railway
line connecting Paris to Versailles and Saint-Germain. He married Mélanie
Bazaine, daughter of Pierre-Dominique Bazaine
(mathematician and bridge and canal engineer), and older sister of
Pierre-Dominique (Adolphe) Bazaine (railway
engineer) and Francois
Achille Bazaine (Marshal of France).

## Work

### Thermodynamics

In 1834, he made his first contribution to the creation of
modern thermodynamics by publishing a report entitled the
*Driving force of the heat* (*Puissance motrice de la
chaleur*), in which it developed the work of the physicist Nicolas Léonard Sadi
Carnot, deceased two years before. Though Carnot had developed
a compelling analysis of a generalised heat engine, he had employed the clumsy and
already unfashionable caloric theory.

Clapeyron, in his memoire, presented Carnot's work in a more
accessible and analytic graphical form, showing the Carnot cycle as a
closed curve on an indicator
diagram, a chart of pressure against volume (named in his honor
Clapeyron's graph).

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.

## Other
work

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^{[1]}
(Clapeyron's theorem).

## Publications

- Clapeyron E. (1834), Puissance motrice de la chaleur,
*Journal de l'École Royale Polytechnique*, Vingt-troisième
cahier, Tome XIV, 153-190.

## Honors

## See also

## References

## External
links