Contributions to the Data on Theoretical Metallurgy: [Part] 11. Entropies of Inorganic Substances: Revision (1948) of Data and Methods of Calculation Page: 40
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40 CONTRIBUTIONS TO DATA ON THEORETICAL METALLURGY
The entropy of Cs2(g) is estimated here as S2098.6=66.6 + 1.5.
Cesium Ion.-From thermal data for the reaction CsC104(c)=
Cs+(aq.) +C104-(aq.), Latimer, Pitzer, and Smith (325) computed
S298.168-31.8 0.6 for Cs+(aq.)
Bromide.-Molecular-constant data estimated by Stevenson (467)
give S298.16=-63.50.5 for CsBr(g). Niwa (380) estimated S298.16-
63.8 + 1.7 from vapor-pressure data and an assumed entropy of
CsBr(c). The former value is adopted.
Chloride.-From molecular-constant data listed by Stevenson (467),
S298.16=61.3-0.5 for CsCl(g). Niwa (380) estimated a lower and
less-certain value, S298s.16=58.9 +2.0, from vapor-pressure data and an
assumed entropy for CsCl(c).
Hydride.-Available molecular-constant data (212) lead to St+r,298.16
=51.20, S ,298.16=0.15, and S98s.16=51.35I0.10 for CsH(g).
Iodide.-Stevenson's (467) suggested molecular-constant data for
CsI(g) give S9.=16 65.2 0.5.
Perchlorate.-Pitzer, Smith, and Latimer (391) (150-2930)
measured the heat capacity of CsCO14(c). There are computed
S15.0= 0.82 (extrapolation) and S9s8.16-Si.o=41.07, making S298.16=
Cesium-Aluminum Sulfate.-The heat capacity of CsAl(SO4)2.12H20
was measured by Latimer and Greensfelder (320) (180-2980). The
entropy calculation results in S298.16= 163 5. The extrapolation
below 17.780 is 3.00.
Element.-The low-temperature heat capacity of Cl2 was measured
by Eucken and Karwat (149) (210-1970) and Giauque and Powell
(184) (140-2370). Relying on the work of the latter investigators,
whose calculations have been checked and are repeated here, there are
obtained S15.0= 0.33 (extrapolation), S 72.12-S1.-= 16.57 (crystals),
AS172.12-1,531/172.12 8.89 (fusion), S39a.0s-S72.12*5.23 (liquid),
AS239.05=4,878/239.05= 20.41 (vaporization at 1 atm. pressure),
AS239.05=0.12 (correction to ideal gas state), S,98.1-839.05= 1.76 (gas).
The sum is Ss.16=-53.310.10.
Giauque and Overstreet (183) have computed the entropy of
C12 (g) from spectroscopic data. They find S29s=18--53.24 for
C1235'35(g), S98.16-o53.39 for C1235'37(g), S2916=53.54 for C1237,37(g), and
S298.16= 53.31 for the ordinary isotopic mixture.
Molecular-constant data (212, 311), I=113.9X10-40 and <w=651
(1), for C1235,35(g) yield S'+ ,298.16=52.70, S,29s.16=0.52, and S298.16
53.22, which is in good agreement with Giauque and Overstreet's more
accurately calculated value.
An independent method of obtaining the entropy of ordinary C12(g)
is offered by the data of Gerke (169), who, by means of measurements
on cells, obtained ASs98.16 -13.7 for the reaction Ag(c)+Y C12(g)=
AgCl(c). This result and the entropies of Ag(c) (10.200.05) and
AgCl(c) (23.0+0.10) lead to S2Ns.16=53.00.4 for C12(g).
The value adopted for the ordinary isotopic mixture is Giauque and
Overstreet's calculated value, S98.16= 53.310.01 for C12(g).
The entropy of monatomic Cl(g) may be obtained from the Sackur
equation and spectroscopic data. At 298.160 only two energy levels
need be considered, the 2P 2 and 2P~/2, having a separation of 881 cm.-'
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Kelley, K. K. Contributions to the Data on Theoretical Metallurgy: [Part] 11. Entropies of Inorganic Substances: Revision (1948) of Data and Methods of Calculation, report, 1950; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc12637/m1/44/: accessed April 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.