Thermodynamics of the xanthoconite-proustite and pyrostilpnite-pyrargyrite phase transition as determined by abrasive stripping voltammetry |
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| Authors: | Birgit Lange Fritz Scholz Hans-Joachim Bautsch Ferdinand Damaschun Gert Wappler |
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| Institution: | 1. Humboldt-Universit?t, Fachbereich Chemie, Institut für Analytische Chemie, Hessische Strasse 1-2, O-1040, Berlin, Germany
2. Humboldt-Universit?t, Museum für Naturkunde, Mineralogisch-Petrographisches Institut und Museum, Invalidenstrasse 43, O-1040, Berlin, Germany
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| Abstract: | The electrochemical reduction of xanthoconite, proustite, pyrostilpnite, and pyrargyrite was studied by abrasive stripping voltammetry, a technique which is based upon a preliminary mechanical transfer of trace amounts of the mineral onto the surface of a paraffin impregnated graphite electrode. Because the electrochemical reduction proceeds near to reversibility and is very similar for each pair of minerals, the peak potentials in differential pulse voltammetry can be used to calculate the standard enthalpy of phase transformation of xanthoconite to proustite and of pyrostilpnite to pyrargyrite:  T
H
(xanth  proust)
O = 35.46 ± 14.15 kJ/mol and T
H
(pyrostilp pyrarg)
O = 38.85 ± 6.60 kJ/mol. These values are not accessible otherwise until now. |
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