Galvanic Cells for the Determination of the Standard Molar Free Energy of Formation of Metal Halides, Oxides, and Sulfides at Elevated Temperatures

Abstract

The use of electromotive force measurements on galvanic cells for the determination of standard molar free energies of formation of halides, oxides, sulfides, and other compounds at elevated temperatures is surveyed. New potentialities and inherent limitations are shown. Formulas for the estimate of errors resulting from electronic conduction and from transference of the components of electrolytes between different activity levels are derived.

The Determination of Phase Boundaries and Thermodynamic Functions in the Iron-Oxygen System by EMF Measurements

“…The standard molal free energies of formation of oxides such as FeO (1, 2), Fe304 (1), CoO (1, 2), Cu._,O (3), NiO (1,2), and MoO2 (4) have been determined at elevated temperatures in numerous studies.…”

Thermodynamics and nonstoichiometry in the intermetallic compound Pt 3 In

“…Three different types of solid state galvanic cells based on the principles outlined by Kiukkola and Wagner [10] were used for the determination of the thermodynamic properties of the Pt 3 In-phase as a function of temperature and composition. Measuring the emf of a cell À ð Þ In; In 2 O 3 ZrO 2 stabilized by CaO or Y 2 O 3 ð Þ Pt 3 In; …”

Electrochemical magnesium sensors for Use in aluminum processing

“…The molten electrolyte must be kept separate from the reference electrode and electrically isolated from the connecting wire to ensure establishment of the correct reference potential. This requirement is eliminated with the use of a solid electrolyte, since the inside of the solid elec- Solid Tube (no frit) MgO·xAlP3 Sodium tains a three-phase mixture of NaF, Na3AlF6' and molten aluminum as the reference electrode, which establishes a constant sodium activity according to 6NaF(s) + Al(l) = Na 3 A1F 6 (s) + 3Na(l) (10) where the sodium is dissolved in the molten aluminum. The cell voltage is related to the difference between the sodium ion activities at the two electrodes according to equation 11 Em = RT In(a Na """""" 1 (11) 2F aNa olIoy so an auxiliary electrode is necessary to relate the magnesium content in the alloy to a sodium activity.…”