William Francis Giauque


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(1895–1982) Canadian–American physical chemist

Born at Niagara Falls in Canada, Giauque spent his whole academic life at the University of California. He began as a student, obtaining his PhD in 1922, and was immediately appointed to the staff at Berkeley, becoming professor of chemistry in 1934.

Giauque was one of the pioneer workers in low-temperature phenomena. His early work in the 1920s concerned the experimental measurement of entropies at very low temperature – work that depended on the use of the third law of thermodynamics introduced in 1906 by Walther Nernst (the Nernst heat theorem). At the same time, Giauque used statistics to calculate the absolute entropies using the energy levels of molecules obtained from spectroscopy. This method, developed by Josiah Willard Gibbs and others, is known as statistical mechanics. Giauque's work provided support for the validity of both statistical thermodynamics and the third law.

Moreover, it led him to a method of attaining very low temperatures, close to absolute zero. The lowest temperature achieved at that time was 0.8 K, reached by Heike Kamerlingh-Onnes in 1910 by pumping away the vapor of liquid helium and causing it to evaporate under reduced pressure. Giauque, and independently Peter Debye, proposed in 1925 a completely different method known as adiabatic demagnetization.

The basic idea is to take a paramagnetic substance surrounded by a coil of wire in a gas-filled container. The sample can be cooled by surrounding the container by liquid helium and magnetized by a current through the coil. It is thus possible to produce a magnetized specimen at liquid-helium temperature, and then to isolate it in a vacuum by removing the gas from the container. Within the magnetized specimen the ‘molecular magnets’ are all aligned. If the magnetic field on the specimen is reduced to zero the sample is demagnetized, and in this process the molecular magnets become random again. The entropy increases and work is done against the decreasing external field, causing a decrease in the temperature of the specimen.

There were considerable problems in putting this theory into practice, not least in measuring the temperatures produced. In 1933 Giauque had a working apparatus that improved on Kamerlingh-Onnes's in achieving a temperature of 0.1 K. Giauque received the 1949 Nobel Prize for chemistry for his work on low-temperature phenomena.

He also worked on isotopes, showing in 1929 (with H. L. Johnson) that oxygen was a mixture of 16O, 17O, and 18O.

Subjects: Science and Mathematics.

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