David Homan 1 of 8 “Giauque's achievements in the field of ...

David Homan
“Giauque’s achievements in the field of chemical thermodynamics and
especially his work on the behaviour of matter at low temperatures and his
closely allied studies of entropy comprise one of the most significant
contributions to modern physical chemistry.” –Professor A. Tiselius in his
1949 Nobel Prize presentation speech to William Francis Giauque
Giauque’s Nobel Prize:
William Francis Giauque, born May 12 th , 1895, in Niagara Falls, Canada, was awarded
the Nobel Prize in chemistry for 1949. The award recognized many years worth of scientific
discovery and many contributions to chemistry especially in the area of the entropy of chemical
substances, particularly at very low temperatures. Giauque’s later experiments were influenced
greatly while he was still a graduate student by Professor Raymond T. Birge of the University of
California at Berkeley’s physics department. Through Professor Birge Giauque obtained an
understanding of the applicability of quantum statistics to the calculation of the absolute entropy
of any gas of diatomic molecules from spectroscopic data. He realized this would be an ideal
1 of 8

David Homan
reference to compare experimental values of entropy. As a result, he set out to test the third law
of thermodynamics.
Through amazing experimental skill he was able to design techniques for obtaining
accurate measurements at temperatures nearing absolute zero. While preparing to present a
seminar on the relationship between magnetism and thermodynamics in 1924, Giauque
postulated about adiabatic demagnetization. He freely discussed his thoughts about adiabatic
demagnetization with colleagues in Berkeley where he was a professor, but did not publish a
paper on his idea until 1927. In March of 1933, while working with a student named D.P.
MacDougall, Giauque finally carried out the first adiabatic demagnetization experiment yielding
0.25 K. Adiabatic demagnetization was a means to allow Giauque to pursue his primary interest:
entropy and the third law of thermodynamics. He was a meticulous experimenter who took
extremely accurate absolute measurements with his goal being an accuracy of 0.1%.
Giauque’s field of study was not just limited to low temperature entropy measurements,
but also to measuring the heat capacities and heats of transition of the halogen acids from very
low temperatures to their boiling points, studying the spectra of diatomic molecules leading to
the discovery of the isotopes of oxygen in 1929, and determining the difference in entropy
between the glass form and the crystalline form of glycerine. Overall, throughout his career he
published scientific work in 75 papers.
The Entropy of Hydrogen chloride:
The purpose for determining the calorimetric entropy of a halogen acid was the testing of
the third law of thermodynamics as well as to compare the data collected with the previous data
obtained from various theories with the aid of spectroscopic data. Hydrogen chloride was used
2 of 8

David Homan
because of the reliability of its spectra measurements and the reliability of its spectra
interpretation. However, the preparation of pure anhydrous hydrogen chloride in quantities large
enough for the experiment was one of the most difficult challenges solved for this particular
determination by Giauque. 3.5 moles were required to fill the calorimeter, but as much as 10
moles was used to account for losses throughout the experiment.
The hydrogen chloride was extensively processed to prepare it for measurement. Two
problems Giauque ran into during the purification process were: the condensed hydrogen
chloride “was of a reddish pink color” and solid white particles appeared in the colorless liquid
upon melting therefore hinting at impurities. Giauque later hypothesized that the reddish pink
material was an unstable crystalline form of hydrogen chloride only present when the hydrogen
chloride was at the temperature of liquid air. The white particles were hypothesized to be
phosphorus oxychloride which can be prepared by the interaction of hot hydrogen chloride with
phosphorus pentoxide.
Once Giauque and Wiebe had obtained purified anhydrous hydrogen chloride he
determined the vapor pressures of the solid form. The results are given in the table below
(Figure 1). They calculated the pressures given in the fourth column using the equation: log P
(cm Hg) = -1114/T – 1.285logT – 0.0009467T + 11.00500. The constants were chosen to fit the
observed data.
3 of 8

David Homan
T, K P obs. (cm Hg) P calc. T obs. - T calc.
132.48 0.558 0.554 -0.05
132.82 0.589 0.580 -0.12
135.2 0.787 0.797 0.10
139.23 1.308 1.310 0.01
143.00 2.044 2.041 -0.01
145.77 2.782 2.783 0.00
148.44 3.705 3.709 0.01
154.29 6.692 6.710 0.03
155.04 7.221 7.215 -0.01
158.91 10.370 10.371 0.00
10.371
Figure 1. Vapor Pressures of Solid Hydrogen Chloride (Giauque and Wiebe, 105)
He also determined the vapor pressures of liquid hydrogen chloride and these results are
given in Figure 2. The calculated pressures given in the fourth column were obtained from the
equation developed by Henning and Stock 1 : log P (mm Hg) = -905.53/T + 175logT – 0.005077T
+ 4.65739.
T, K P obs. (cm Hg) P calc. T obs. - T calc.
158.91 10.371 10.357 -0.02
164.62 16.29 16.260 -0.03
169.28 22.98 22.930 -0.03
173.95 31.71 31.720 0.00
178.53 42.81 42.830 0.01
181.84 52.64 52.650 0.00
185.17 64.34 64.290 -0.01
188.41 77.48 77.470 0.00
191.96 94.39 94.280 -0.02
195.93 116.510 116.330 -0.03
Figure 2. Vapor Pressures of Liquid Hydrogen Chloride (Giauque and Wiebe, 106)
For the vapor pressure measurements a copper sheathed glass apparatus was used, but it
was not employed for the calorimetric measurements because of experience of others at
Giauque’s laboratory that glass calorimeters were inferior mainly because the accuracy is
decreased by the poor thermal conductivity. So, for the calorimetric measurements, Giauque and
Wiebe designed a sophisticated apparatus made from gold sheet 0.75 mm in thickness with
welded seams. In order to correct a known source of error energy was introduced into the
4 of 8

David Homan
system. The source of this energy was a combined thermometer-heater that also allowed the
measurement of temperature intervals. This resistance thermometer, after calibration, was found
to be so precise that its accuracy was within 0.05 K.
Next they obtained the heat capacity of hydrogen chloride using his new calorimeter.
Because they knew energy was being input into the system they were able to calculate the heat
capacities within the range of 17.29 K to 188.07 K. The data is presented in Figure 3. The
density of solid hydrogen chloride was determined by Simon and Simson 2 and the density of
liquid hydrogen chloride has been determined by Baumg and Perrot 3 .
T, K C p /mole (cal/deg) T, K C p /mole (cal/deg) T, K C p /mole (cal/deg)
17.29 1.031 67.85 5.848 117.30 10.14
21.34 1.637 72.63 6.159 123.92 10.46
24.71 2.066 75.46 6.329 131.18 10.67
26.85 2.330 77.65 6.526 138.79 10.95
28.10 2.491 80.25 6.712 148.90 11.34
31.89 2.943 82.63 6.894 155.06 11.65
35.82 3.393 84.69 7.053 158.91 Melting point
39.95 3.794 87.70 7.327 163.72 13.89
44.20 4.132 88.79 7.410 171.45 13.95
48.62 4.472 92.83 7.786 171.74 13.95
51.23 4.677 92.96 7.849 178.64 14.01
56.01 5.070 98.36 Transition 185.20 14.07
58.94 5.231 103.01 9.64 188.07 Boiling point
63.31 5.550
Figure 3. Heat Capacity of Hydrogen Chloride (Giauque and Wiebe, 110)
For their calculation of the entropy of hydrogen chloride, Giauque and Wiebe determined
heats of transition, fusion, and vaporization. Heats of fusion and transition were measured by
inputting heat at a temperature below the melting or transition temperature and ending the input
just above. The heat of transition was determined to be 98.36 K and the average ÈH was 284.3
cal mol -1 . The heat of fusion was determined to be 158.91 K and the average ÈH was 476.0 cal
1 Henning and Stock, Z. Physik, 4, 226 (1921).
2 Simon and Simson, Z. Physik, 21, 168 (1924).
5 of 8

David Homan
mol -1 . To calculate the heat of vaporization at atmospheric pressure two methods were used, but
both methods determined the amount of material evaporated by absorption in a solution of
sodium hydroxide. The results for methods I and II were 3859 ± 9 cal mol -1 and 3860 ± 4 cal
mol -1 respectively. Giauque and Wiebe felt more confidence in method II because the results
from this method showed a smaller deviation from the mean than the results from method I.
The entropy of hydrogen chloride was obtained by graphical integration of the equation S
= fC p dlnT (from 0 to T) plus the entropy changes accompanying each change of state. The
Debye function (C p ≅ T 3 ) was employed below the lowest temperature of measurement.
Giaque’s and Wiebe’s entropy calculations are summated in Figure 4.
Solid stable below 98.36 K S (cal K -1 mol -1 )
0 to 16 K, extrapolation 0.30
16 K to 98.36 K, graphical 7.06
Transition 284.3/98.35 = 2.89
Solid stable above 98.36 K
98.36 K to 158.91 K, graphical 5.05
Fusion 476.0/158.91 = 3.00
Liquid
158.91 K to 188.07 K, graphical 2.36
Vaporization, 3860/88.07 = 20.52
Entropy of HCl (g) at boiling pt. =
41.2 +/- 0.1 E.U.
Figure 4. Calculation of Entropy of Hydrogen Chloride (Giauque and Wiebe, 116)
Giauque and Wiebe tested their results by calculating the entropy for hydrogen chloride
using spectroscopic data. Using two different methods, they concluded that the value for entropy
using the spectroscopic data was very similar to their calorimetric value. They summarized this
finding by saying, “The close agreement of our experimental and theoretical values is very good
evidence, not only for the validity of the theoretical considerations as closely approximating the
actual properties of the substance, but also for the third law of thermodynamics.” They further
3 Baumg and Perrot, J. chim. phys., 12, 225 (1914).
6 of 8

David Homan
tested their results by calculating ÈS using Gibbs free energy values for chlorine and hydrogen.
The value obtained for hydrogen chloride using the Gibbs information was 44.5 cal K -1 mol -1
which is very similar to their calorimetric value.
7 of 8

David Homan
Works Cited
“Biography of William Francis Giauque.” URL:
http://www.nobel.se/chemistry/laureates/1949/giauque-bio.html.
Giauque, W.F. and R. Wiebe. “The Entropy of Hydrogen Chloride. Heat Capacity from 16°K.
to Boiling Point. Heat of Vaporization. Vapor Pressures of Solid and Liquid.” Journal
of the American Chemical Society 50:101-22.
“Noble Prize in Chemistry 1949- Prize Presentation.” URL:
http://www.nobel.se/chemistry/laureates/1949/press.html.
Pitzer, Kenneth S. and David A. Shirley. “William Francis Giauque, May 12, 1895-March 28,
1982.” URL: http://bob.nap.edu/html/biomems/wgiauque.html.
8 of 8