Contributions to the Data on Theoretical Metallurgy: [Part] 11. Entropies of Inorganic Substances: Revision (1948) of Data and Methods of Calculation Page: 62
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62 CONTRIBUTIONS TO DATA ON THEORETICAL METALLURGY
MgC12.4H20(c). There are calculated S.12= 5.73 (extrapolated),
S298.16-S0.12:--57.35 (measured), and S298.16- 63.1 0.7.
In addition, Kelley and Moore (293) (540-2960) measured the
heat capacity of MgCl2.6H20(c). There are obtained S50.12- 8.76
(extrapolated), S29s.16-S50.12= 78.75 (measured), and S98.16= 87.5
For MgCl(g), there is estimated S9;s.16 =55.00.5. This is based
upon w=464 (212), quantum weight of the ground statee=2, and an
assumed I= 82 X 10-40.
Chromite.-Shomate (425) (540-2960) measured the heat capacity
of MgCr204(c). The data yield S3.09- 1.63 (extrapolated), S298.16-
S3.09=23.71 (measured), and S209.16=-25.3 0.2.
Fluoride.-The heat capacity of MgF2(c) was measured by Todd
(486) (540-2970). The data yield S,.0--0.54 (extrapolated),
S098s.1-S1.0 13.14 (measured), and S2's.16= 13.68 0.07.
Molecular-constant data (212), I-54.2X 10-40, w= 687, and
quantum weight-2 for the ground state, lead to S+r,29.16 , 51.13,
80.29.1 -0.32, Se,298.16=1.38, and S9s.-52.80.5 for Mg F(g).
Hydrides.-Molecular-constant data (212) are available for MgH(g)
and MgD(g). For the former, 1-4.8X 10-40 and w=1,463; for the
latter, I=9.24 X10-40 and w=1,062. Both have a quantum weight
of 2 for the ground state.
For MglH(g), S+r,298 .1644.720, S,298.16= 0.011, Se,296.16-1,378, and
S2098.16= 46.11 0.10.
The corresponding values for MgD(g) are St+r,298.16= 46.133,
Sv,298.16= 0.072, Sea29s.i-- 1.378, and S,s.1=47.58 10.10.
Hydroxide.-Giauque and Archibald (173) (220-3210) measured
the heat capacity of Mg(OH)2(c). Their caluclations give S98.16=
15.09, of which 0.033 is extrapolation below 21.10. The uncertainty
should not exceed 0.05 unit.
Iodide.-The vibration frequency of the MgI(g) molecule has been
reported (212) as 312 cm.-. This value, quantum weight of 2 for
the ground state, and an estimated value of the moment of inertia,
I= 172X 10-0, lead to S2s.1 59.9 0.5.
Nitrate.-Shomate and Kelley (4 5) (540-2970) measured the heat
capacity of Mg(N03)2(c). There are computed, Sl3.09=4.09 (extra-
polation), S98.16_-S 3.09-35.06 (measured), and Ss98.16=39.20.4.
Silicates.-The heat capacity of MgSiO1 (clinoenstatite) was
measured by Kelley (285) (520-2960) and Wagner (496) (210-360).
The data of Wagner appear to be too high and only those of Kelley are
used in obtaining S0.120.49 (extapolation), S's.1 -S500.12= 15.73
(measured), and S298.16 16.22 0.10.
Kelley(285)(53'-2950) also measured the heat capacity of Mg2SiO4(c).
There are computed S0.12- 0.60 (extrapolation), S' s.1s-S0.12=22.15
(measured), and Sios.16 22.75 0.2.
Sulfate.-The heat capacity of MgSO4(c) was measured by Moore
and Kelley (365) (530-2960). There are obtained S0.12 =1.10 (extra-
polation), Ss98.16--S0.12-20.78 (measured), and Sys.16= 21.9 0.2.
Titanate.-Shomate (430) (520-2970) measured the heat capacity
of MgTiO3(c). His data yield S2.oo= 0.45 (extrapolation), S98s.-16
S2.00=-17.37 (measured), and S ,98.16= 17.82 -0.10.
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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/m1/66/?rotate=90: accessed May 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.