Clapeyron (English spelling) Benoit Paul Emile Clapeyron

French engineer and physicist. Born in Paris. Studied at the Ecole Polytechnique (Polytechnic School), he went to Russia in 1820 and worked as a teacher and engineer in St. Petersburg. Returning to the US in 1830, he worked as a railway engineer, and when the railway between Paris and Saint-Germain was built, he designed and built the locomotive after R. Stevenson declined to design it due to the long gradient. In 1834, he published a paper entitled "On the Motive Power of Heat", in which he fully supported S. Carnot's achievements in thermology and shed light on his ideas by using analytical expressions. Although he was a supporter of the caloric theory, he established a function that later led to the concept of absolute temperature, and derived an important relationship for water vapor (the Clausius-Clapeyron equation). He was the first to express the so-called "Carnot cycle" on a p-v graph, which had a great influence on Kelvin and Clausius. He continued to be interested in steam engines throughout his life, but he himself did not develop the problem in an original way. In 1848 he became a member of the Academy of Sciences, where he was active in such committees as planning the Suez Canal and the application of steam power to warships.

[Susumu Takayama]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

フランスの技術者、物理学者。パリ生まれ。エコール・ポリテクニク（理工科大学校）に学び、1820年ロシアに行き、ペテルブルグで教師、技師を務めた。1830年に帰国、鉄道技師として働き、パリ―サン・ジェルマン間の鉄道敷設の際は、R・スティーブンソンが長い勾配(こうばい)のために機関車の設計を辞退した後を受けて、その設計、製造を行った。1834年「熱の動力について」という論文を発表、S・カルノーの熱学の業績を全面的に支持し、解析的表現をとることでその考えに光をあてた。熱素説の立場にいたが、後の絶体温度の概念につながる関数を設定し、また水蒸気についての重要な関係式（クラウジウス‐クラペイロンの式）を導いた。いわゆる「カルノー・サイクル」をp‐vグラフに初めて表現し、ケルビンやクラウジウスに多大の影響を与えた。生涯、蒸気機関に関心をもち続けたが、彼自身、独創的に問題を発展させることはなかった。1848年科学アカデミーの委員になり、スエズ運河の計画や、軍艦に蒸気力を応用する計画の委員会などで活躍した。

［高山　進］

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