Contributions to the Data on Theoretical Metallurgy: [Part] 11. Entropies of Inorganic Substances: Revision (1948) of Data and Methods of Calculation Page: 74
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74 CONTRIBUTIONS TO DATA ON THEORETICAL METALLURGY
The entropy of sublimation of P(c) (black), AS 8.16= 45.58 (270)
and the entropy of P4(g) lead to S98.16=5.30.5 for P(c) (black)
Oxide.-The entropy of PO(g) is obtainable from molecular-
constant data (212), I-36.7X10-40 and <=1,224, and the term
values of the two lowest electronic states (each of quantum weight 2),
0 and 221 cm.-1 There are computed So+7,29.16= 50.601, S~,298.16
0.037, and Se,298.18=2.510. The sum is S298.16=53.150.10 for
Tribromide.-Howard and Wilson (217) have given dimensions of the
PBr3(g) molecule that correspond to I,= 1,650 X 10-40 and I2=3-865
X 10-40, and have reported the vibration frequencies as 116 (2), 162
(1), 380 (2), and 400 (1) cm.-1 There are calculated S +,298.18=
71.40, S;,2981s.1=11.87, and S2zs.13-83.31.0. A similar result, 83.1,
was calculated by Stevenson and Yost (470).
Chlorides.-From dimensional data given by Howard and Wilson
(217), the moments of inertia of the PC13(g) molecule are I1=585 X
10-4o and 12=3=325 X10-40. The vibrational frequencies are 190
(2), 257 (1), 480 (2), and 510 (1). These values lead to S+r,298.16-
66.40, S~,29s.6 8.18, and S298.16 74.6 1.0. The last value is in
substantial agreement with the calculations of Anderson and Yost (26)
and Stevenson and Yost (470).
From heat and free-energy-of-vaporization values given by Kelley
(270), the entropy of vaporization of PC13(1) is AS2'9s.16-22.50. This
leads to S29s.16=52.1 2.0 for PCl3(1), which also is in substantial
agreement with the result calculated by Anderson and Yost (26).
Stevenson and Yost (470) have estimated S0298.16=84.3 for PC5(g).
The uncertainty is estimated here as 2.0. This value supersedes
the earlier result reported by Anderson and Yost (26).
Trifluoride.-Howard and Wilson (217) have reported dimensional
data for the PF3(g) molecule which correspond to 1- =178X 10-40 and
I2 -13106X10-40. The vibration frequencies are 486 (2), 531 (1),
840 (2), and 890 (1) cm.-1 There are computed S?+r,298.16- 61.67
and S,29s.8--2.48. The sum is S298.16-=64.1 0.3, in virtually exact
agreement with the value calculated by Stevenson and Yost (470).
Hydrides.-Clusius and Frank (96) (110-1860) and Stephenson and
Giauque (459) (150-1860) have measured the heat capacity of phos-
phine, PH3, at low temperatures. This substance undergoes transi-
tions in the solid state at 49.430 and 88.100, and it is possible to super-
cool the form stable between these temperatures. When this is done,
however, the supercooled form itself undergoes a transition at 30.290.
Stephenson and Giauque have straightened out very satisfactorily the
energy relationships among these crystalline species. The data of
Clusius and Frank are somewhat lacking in this respect.
The calculations of Stephenson and Giauque have been checked
and are repeated here. For PH3(c), supercooled below 49.430,
they find S5.00o=0.495 (extrapolation), S0.29_-S .00o-2.185 (crystals
II'), AS30 .29=19.6/30.29=0.647 (transition), and S29.43S0S3.29=4.800
(crystals II). The sum is S9.43-8.13. For the variety stable below
49.43', S .oo= 0.338 (extrapolation), S49.43- So5o.004.041 (crystals III),
and AS9.43 =185.7/49.43=3.757 (transition). The sum for this path
is S~,.43-8.14. The agreement between these two values of S49.43
constitutes a good test of the third law of thermodynamics. The
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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/m1/78/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.