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Chemistry

Chemists invoke bizarre Maxwell's demon on the largest scale yet

A 19th-century thought experiment that was once thought to defy the laws of thermodynamics has now been realised to make molecules accumulate on one side of a U-bend

By Alex Wilkins

18 June 2024

Physicist James Clerk Maxwell proposed his demonic thought experiment in 1867
SSPL/Science Museum/Getty Images

A chemical pump based on a 19th-century thought experiment involving an invisible “demon” could be used to help separate chemicals in drug manufacturing.

Maxwell’s demon, first proposed by physicist James Clerk Maxwell in 1867, involves two boxes of gas separated by a weightless door that is controlled by a tiny demon. The demon only lets faster-moving particles pass through in one direction and slower particles pass in the other direction, which makes one box hotter and the other cooler. But this seems to violate the …

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