William Giauque

William Francis Giauque was born in Niagara Falls, Ontario, on 12 May 1895, to American parents. His father died when he was in his teens and he left school to work at the Hooker Electrochemical Company in Niagara Falls, New York, intending to become an engineer; the two years he spent in its laboratory redirected him to chemistry. He entered the University of California, Berkeley, in 1916, took his doctorate there in 1922 under George Ernest Gibson, and never left — he taught at Berkeley for the rest of his life.

Giauque's subject was the third law of thermodynamics, and specifically its verification. Nernst's heat theorem asserts that entropy tends to a constant as T → 0, and Planck sharpened it to zero for a perfect crystal, but these were claims about a limit nobody could reach. Giauque's programme was to measure low-temperature heat capacities precisely enough to integrate S = ∫ C/T dT up from near zero and compare the answer with the spectroscopic entropy calculated from statistical mechanics. Where the two disagreed, something interesting was happening.

They disagreed, informatively. Giauque and Herrick Johnston's analysis of the entropy of oxygen led them in 1929 to discover the isotopes ¹⁷O and ¹⁸O — found in a thermodynamic discrepancy rather than a mass spectrometer, and forcing a revision of the atomic-weight scale. Other discrepancies turned out to be residual entropy: substances like CO and ice whose ground states are not unique, frozen into disorder as they cool, and which therefore keep a stubborn entropy at T → 0 in apparent defiance of Planck's statement.

To reach the temperatures the programme demanded, Giauque proposed in 1927 — independently of Debye's 1926 suggestion — cooling by adiabatic demagnetisation of a paramagnetic salt, and in 1933 built the apparatus and reached 0.25 K on the first run. It broke a deadlock that had held since Onnes stalled near 0.83 K a decade earlier, and it opened the millikelvin range. He received the 1949 Nobel Prize in Chemistry. He died in Berkeley on 28 March 1982.