• journal_title：American Mineralogist
• Contributor：Evgeniy G. Osadchii ; Olga A. Rappo
• Publisher：Mineralogical Society of America
• Date：2004-
• Format：text/html
• Language：en
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：89
• issue：10
• firstpage：1405
• section：Articles

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:

The EMF temperature dependences observed for these reactions, together with auxiliary thermodynamic properties for Ag₂S, acanthite, from Robie and Hemingway (1995), result in the following standard thermodynamic properties at 298.15 K and 1 bar (10⁵ Pa): Δ_fG^o(Ag₃AuS₂, cr) = −69478(200) J/mol and S^o(Ag₃AuS₂, cr) = 273.37(56) J/(mol·K) (uytenbogaardtite), Δ_fG^o (AgAuS, cr) = −27621(210) J/mol and S^o(AgAuS, cr) = 128.11(60) J/( mol·K) (petrovskaite), and Δ_fG^o (Au₂S, cr) = 1077(650) J/mol and S^o(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.