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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2017: 2.645

CiteScore 2017: 2.31

SCImago Journal Rank (SJR) 2017: 1.440
Source Normalized Impact per Paper (SNIP) 2017: 1.059

Online
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1945-3027
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Volume 89, Issue 10

Issues

Determination of standard thermodynamic properties of sulfides in the Ag-Au-S system by means of a solid-state galvanic cell

Evgeniy G. Osadchii
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  • Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, Moscow District 142432, Russia
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/ Olga A. Rappo
  • Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, Moscow District 142432, Russia
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Published Online: 2015-03-28 | DOI: https://doi.org/10.2138/am-2004-1007

Abstract

Thermodynamic properties of the following phase reactions in the Ag-Au-S system have been investigated via electromotive force (EMF) measurements in solid-state galvanic cells with Ag4RbI5 as a solid electrolyte:

Ag(cr) + Ag3AuS2(cr) = 2Ag2S(cr) + Au(cr)

Ag(cr) + 2AgAuS(cr) = Ag3AuS2(cr) + Au(cr)

Ag(cr) + Au2S(cr) = AgAuS(cr) + Au(cr)

AgAuS(cr) + Ag2S(cr) = Ag3AuS2(cr)

The EMF temperature dependences observed for these reactions, together with auxiliary thermodynamic properties for Ag2+S, acanthite, from Robie and Hemingway (1995), result in the following standard thermodynamic properties at 298.15 K and 1 bar (105 Pa): ΔfGo(Ag3AuS2, cr) = -69478(200) J/mol and So(Ag3AuS2, cr) = 273.37(56) J/(mol·K) (uytenbogaardtite), ΔfGo(AgAuS, cr) = -27621(210) J/mol and So(AgAuS, cr) = 128.11(60) J/(mol·K) (petrovskaite), and ΔfGo(Au2S, cr) = 1077(650) J/mol and So(Au2S, cr) = 128.1(2.0) J/(mol·K). Au2S(cr) is a thermodynamically metastable phase, but the values of its thermodynamic functions are open to discussion

About the article

Received: 2004-01-09

Accepted: 2004-02-25

Published Online: 2015-03-28

Published in Print: 2004-10-01


Citation Information: American Mineralogist, Volume 89, Issue 10, Pages 1405–1410, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am-2004-1007.

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© 2015 by Walter de Gruyter Berlin/Boston.

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