Determination of melanterite-rozenite and chalcanthite-bonattite equilibria by humidity measurements at 0.1 MPa
-
I-Ming Chou
,
R.R. Seal ii
Abstract
Melanterite (FeSO4·7H2O)-rozenite (FeSO4·4H2O) and chalcanthite (CuSO4·5H2O)-bonattite (CuSO4·3H2O) equilibria were determined by humidity measurements at 0.1 MPa. Two methods were used; one is the gas-flow-cell method (between 21 and 98 °C), and the other is the humiditybuffer method (between 21 and 70 °C). The first method has a larger temperature uncertainty even though it is more efficient. With the aid of humidity buffers, which correspond to a series of saturated binary salt solutions, the second method yields reliable results as demonstrated by very tight reversals along each humidity buffer. These results are consistent with those obtained by the first method, and also with the solubility data reported in the literature. Thermodynamic analysis of these data yields values of 29.231 ± 0.025 and 22.593 ± 0.040 kJ/mol for standard Gibbs free energy of reaction at 298.15 K and 0.1 MPa for melanterite-rozenite and chalcanthite-bonattite equilibria, respectively. The methods used in this study hold great potential for unraveling the thermodynamic properties of sulfate salts involved in dehydration reactions at near ambient conditions.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Study on adsorption of submicrometer gold on kaolinite by quantum chemistry calculations
- Image distortion in scanning probe microscopy
- Multiple length scale growth spirals on metamorphic graphite {001} surfaces studied by atomic force microscopy
- 29Si MAS NMR study of diopside–Ca-Tschermak clinopyroxenes: Detecting both tetrahedral and octahedral Al substitution
- Electron paramagnetic resonance spectroscopic study of synthetic fluorapatite: Part I. Local structural environment and substitution mechanism of Gd3+ at the Ca2 site
- Electron paramagnetic resonance spectroscopic study of synthetic fluorapatite: Part II. Gd3+ at the Ca1 site, with a neighboring Ca2 vacancy
- Determination of the H3BO3 concentration in fluid and melt inclusions in granite pegmatites by laser Raman microprobe spectroscopy
- Analysis of natural H2O + CO2 + NaCl fluid inclusions in the hydrothermal diamond anvil cell
- Thermodynamics of the amphiboles: Ca-Mg-Fe2+ quadrilateral
- Phase boundary between rutile-type and CaCl2-type germanium dioxide determined by in situ X-ray observations
- The nature, formation, and stability of end-member illite: A hypothesis
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- Pressure-temperature paths from garnet-zoning: Evidence for multiple episodes of thrust burial in the hinterland of the Sevier orogenic belt
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- Closure in crystal size distributions (CSD), verification of CSD calculations, and the significance of CSD fans
- Icosahedral domain structure of framboidal pyrite
