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Acquisition and evaluation of thermodynamic data for bieberite-moorhouseite equilibria at 0.1 MPa

I-Ming Chou and Robert R. Seal
Acquisition and evaluation of thermodynamic data for bieberite-moorhouseite equilibria at 0.1 MPa (in An Ernstfest festschrift; mineralogy and petrology of high P/T terranes, P-T-ometry, and experimental phase relations, Sorena S. Sorensen (prefacer) and William Carlson (prefacer))
American Mineralogist (May 2005) 90 (5-6): 912-917

Abstract

Published estimates for the equilibrium relative humidity (RH) at 25 degrees C for the reaction: bieberite (CoSO (sub 4) .7H (sub 2) O) = moorhouseite (CoSO (sub 4) .6H (sub 2) O) + H (sub 2) O, range from 69.8 to 74.5%. To evaluate these data, the humidity-buffer technique was used to determine equilibrium constants for this reaction between 14 and 43 degrees C at 0.1 MPa. Reversals along five humidity-buffer curves yield ln K = 18.03-6509.43/T, where K is the equilibrium constant, and T is temperature in K. The derived standard Gibbs free energy of reaction is 9.43 kJ/mol, which agrees well with several previously reported values based on vapor-pressure measurements. It also agrees well with values calculated from the data derived mostly from calorimetric measurements. Previous studies indicated that the temperature of the invariant point for the assemblage bieberite-moorhouseite-aqueous solution-vapor is near 44.7 degrees C, and our extrapolated data predict 91.1% RH at this temperature; the predicted position for the invariant point is in excellent agreement with those reported previously.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 90
Serial Issue: 5-6
Title: Acquisition and evaluation of thermodynamic data for bieberite-moorhouseite equilibria at 0.1 MPa
Title: An Ernstfest festschrift; mineralogy and petrology of high P/T terranes, P-T-ometry, and experimental phase relations
Author(s): Chou, I-MingSeal, Robert R., II
Author(s): Sorensen, Sorena S.prefacer
Author(s): Carlson, Williamprefacer
Affiliation: U. S. Geological Survey, Reston, VA, United States
Affiliation: Smithsonian Institution, National Museum of Natural History, Washington, DC, United States
Pages: 912-917
Published: 200505
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
Meeting name: 2003 annual GSA meeting
Meeting location: Seattle, WA, USA, United States
Meeting date: 20031102Nov. 2-5, 2003
References: 40
Accession Number: 2005-044721
Categories: Mineralogy of non-silicates
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
N32°30'00" - N42°00'00", W124°30'00" - W114°15'00"
Secondary Affiliation: University of Texas at Austin, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200526
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