Heat capacity and entropy at the temperatures 5 K to 720 K and thermal expansion from the temperatures 298 K to 573 K of synthetic enargite (Cu3AsS4)
Journal of Chemical Thermodynamics
By: R.R. Seal II, R. A. Robie, B. S. Hemingway, and H. T. Evans Jr.
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Abstract
The heat capacity of synthetic Cu3AsS4 (enargite) was measured by quasi-adiabatic calorimetry from the temperatures 5 K to 355 K and by differential scanning calorimetry from T = 339 K to T = 720 K. Heat-capacity anomalies were observed at T = (58.5 ?? 0.5) K (??trsHom = 1.4??R??K; ??trsSom = 0.02??R) and at T = (66.5 ?? 0.5) K (??trsHom = 4.6??R??K; ??trsSom = 0.08??R), where R = 8.31451 J??K-1??mol-1. The causes of the anomalies are unknown. At T = 298.15 K, Cop,m and Som(T) are (190.4 ?? 0.2) J??K-1??mol-1 and (257.6 ?? 0.6) J??K-1??mol-1, respectively. The superambient heat capacities are described from T = 298.15 K to T = 944 K by the least-squares regression equation: Cop,m/(J??K-1??mol-1) = (196.7 ?? 1.2) + (0.0499 ?? 0.0016)??(T/K) -(1918 000 ?? 84 000)??(T/K)-2. The thermal expansion of synthetic enargite was measured from T = 298.15 K to T = 573 K by powder X-ray diffraction. The thermal expansion of the unit-cell volume (Z = 2) is described from T = 298.15 K to T = 573 K by the least-squares equation: V/pm3 = 106??(288.2 ?? 0.2) + 104??(1.49 ?? 0.04)??(T/K). ?? 1996 Academic Press Limited.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Heat capacity and entropy at the temperatures 5 K to 720 K and thermal expansion from the temperatures 298 K to 573 K of synthetic enargite (Cu3AsS4) |
| Series title | Journal of Chemical Thermodynamics |
| DOI | 10.1006/jcht.1996.0040 |
| Volume | 28 |
| Issue | 4 |
| Year Published | 1996 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Journal of Chemical Thermodynamics |
| First page | 405 |
| Last page | 412 |
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