Contributions to the Data on Theoretical Metallurgy: [Part] 11. Entropies of Inorganic Substances: Revision (1948) of Data and Methods of Calculation Page: 24
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24 CONTRIBUTIONS TO DATA ON THEORETICAL METALLURGY
constant heat capacity of C,=5/2R=4.969 cal. per deg.). The
resulting third-law value is Ss9.16= 36.95 0.2.
Similar calculations from the data of Eucken and Eucken and
Hauck yield: S7 .s =1.133 (extrapolation), S83.6-S7.s=8.062 (crystals);
AS3 .6=265.2/83.6-=3.172 (fusion), and S S7.-S3 .= 0.453 (liquid).
These items add to give S87.3= 12.82 for the entropy of liquid argon.
These investigators did not measure the heat of vaporization, and the
value from the work of Frank and Clusius will be adopted together
with their correction to the ideal gas state. The result is S87.3=30.79,
which, in turn, leads to S29.16--36.890.2 for argon gas.
The most reliable value for argon gas is that computed from the
Sackur equation, S298,16=-36.99 0.01. The two third-law values are
seen to be in substantial agreement with this result.
Element.-Anderson (8) (570-2910) measured the heat capacity of
As(c). His data give S6.23= 1.20 (extrapolation) and S198.16- S5.23 7. 16
(measured), making S298.16= 8.4 0.2.
Spectroscopic energy-level data for As(g), listed by Moore (364),
show that only the lowest level, with a quantum weight of 4, is effective
at 298.160. Addition of R In 4 to the Sackur equation yields S298s.16=
The vibration frequency, 429.4 cm.-1, and the interatomic distance,
1.95X10-8 cm., of the As2(g) molecule were reported by Almy (6).
From the latter figure, I= 236 X 10-4. There are computed St+r,298.16
56.38 and S;.298.16=0.86, making a total of S29.16= 57.20.3.
From vapor-pressure data the value AS298.16= 35.1 was estimated as
the entropy of sublimation of arsenic in forming As4(g) (270). This
result and the entropy of the solid yield S,9s.18-35.1+4X8.4=69
for As4(g). The error in this value may be several units.
Oxides.-Anderson (8) (As203, 600-297o; and As205, 63"-297")
measured heat capacities of two arsenic oxides.
The data for AS203(c) give S56.23-3.54 (extrapolation), S~9s.18-
S06.23=22.04 (measured), and S98s.16=-25.6 0.5.
The entropy of sublimation of orthorhombic As203 to form As406(g)
was computed as AS8s.-16=49.5 from vapor-pressure data (270). This
value and the entropy of the solid give S2'98.16-49.5+2X 25.6= 101 for
As40(g). The error in this value may be several units.
The data for As201(c) give S.~.1- 1.94 (extrapolation), S298.16-
S.3-123.30 (measured) and S98s.16= 25.20.4.
Arsenious and Arsenic Acids and Ions.-The National Bureau of
Standards Tables (371) record S21s.16-30.3 for HAsO2(aq.), S98s.16
47.0 for H3AsO3(aq.), S2s98.16=49.3 for H3AsO4(aq.), S298.1 =0.9 for
HAsO4--(aq.), and Ss98.16= -34.6 for AsO--(aq.). Stephenson (454)
reported S s98.16= 28.0 1.0 for H2AsO--(aq.).
Trichloride.-Brodskii and Sack (56), Howard and Wilson (217),
Paramasivan (382), Yost (505), and Yost and Anderson (506) have
considered the vibration frequencies of the AsCl3(g) molecule. These
frequencies are 159(2), 193(1), 370(2), and 410(1) cm.-1. Yost and
Anderson also report the moments of inertia, I1=661.8X 10-40 and
1 3-==402.0X 10-o. The symmetry number is 3, as the molecule
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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/m1/28/: accessed April 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.