Contributions to the Data on Theoretical Metallurgy: [Part] 7. The Thermodynamic Properties of Sulphur and its Inorganic Compounds Page: 86
ii, 154 p. : tables ; 24 cm.View a full description of this report.
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DATA ON THEORETICAL METALLURGY.-VII
the limits of error in the properties of Cu20 alone, with results obtain-
able from the values adopted for CuSO4 and SO2 in conjunction with
the figures for Cu20 previously suggested. Thus, for this reaction
there may be written
A C, = 7.28- 13.96 X 10- a T- 2.045 X 105 T-2. (463)
AH298.1=34,240, and AF298.1=16,860. Calculations yield AH0=
32,000 and 1= -12.52 and result in the following relationships:
3Cu+ CuSO4 = 2CuO+ SO,;
AH= 32,000 + 7.28 T- 6.98X 10-3T2 + 2.045 X 10sT-', (464)
AF=-- 32,000 -16.77 Tlog T+6.98 X 10-T2+1.022 X 105 T-'-12.52T, (465)
AH298.1=34,240; AF298.1= 16,860.
When AHo0=32,000 is used in conjunction with 2-calculations from
Schenck and Hempelmann's data, it is found that although the I
values obtained are quite scattered they show no trend with the tem-
perature. The average value is about -11.3. As -Iis the constant
in the entropy-of-reaction equation and as the probable error in the
entropy of Cu20 alone is 1.5, the agreement between this value and
that obtained above is all that can be expected.
Basic sulphate.-From the reactions 4CuSO 4 + Cu2O = 3(CuO.CuSO4)
+SO2 and CuO.CuSO4+ Cu20=4CuO +SO2, the values AH29s.1 ---
227,660 and AF298.1= -193,800 may be computed for the heat and
free energy of formation of CuO.CuSO4 from the elements. The
corresponding figures obtained from the reactions 4CuSO4= 2(CuO.
CuSO4) + 2S02+ 02 and 2 (CuO. CuSO4) = 4CuO+ 2S02+02 are AH298.1
--226,020 and AFO298.1= -193,020. The means, AH298.1= --226,840
and AFs98.1= --193,410, are chosen. As a consequence, there are
obtained AH298.1=-5,150 and AF2s98.1=-4,660 for the reaction
CuO + CuSO4= CuO.CuSO4, provided the figures previously mentioned
for CuO are employed. Although these values cannot be considered
as having much significance, they appear to be of a reasonable order
of magnitude. Their difference indicates that the entropy of CuO.
CuS04 is 1.6 unit lower than the sum of those of CuO and CuSO4,
which also appears reasonable.
Hydration.-There are three well-known hydrates of CuSO4--
CuSO4.H20, CuSO4.3H20, and CuS04.5H20. The dissociation pres-
sure of CuSO4.H20 was measured by Siggel (81, p. 1409) over a range
of temperatures and by Logan (89) at a single temperature, 308.10.
Logan's result, however, disagrees with the data of Siggel, which are
used here. If AC, is ignored and the data plotted as -R In PH20
against 1/T, a line of slope AH=17,500 is obtained; and the corre-
sponding value of I is -37.40, as is seen from the summarized calcu-
lations in table 61.
TABLE 61.-CuSO4.HO= CuSO4 + HO(g)
T Pa2o -R In P20 17,500
372. 1 7. 90X10-3 9. 62 47.03 -37. 41
383. 3 1. 58X10-2 8. 24 45. 66 -37. 42
403. 9 5. 03X10-2 5. 94 43. 33 -37. 39
410.2 7.04X10-2 5.27 42.66 -37.39
420. 4 1. 19X10-1 4. 23 41. 63 -37. 40
Mean -37. 4086
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Kelley, K. K. Contributions to the Data on Theoretical Metallurgy: [Part] 7. The Thermodynamic Properties of Sulphur and its Inorganic Compounds, report, 1937; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc66396/m1/88/: accessed May 13, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.