Revised values for the thermodynamic properties of boehmite, AlO(OH), and related species and phases in the system Al-H-O
- Geological Survey, Reston, VA (United States)
- Lawrence Berkeley Lab., CA (United States)
Heat capacity measurements are reported for a well-characterized boehmite that differ significantly from results reported earlier by Shomate and Cook (1946) for a monohydrate of alumina. The entropy of boehmite derived in this study is 37.19 {plus minus} 0.10 J/(mol{center dot}K) at 298.15K. A review of recent{sup 27}Al solution NMR data and other experiments has shown that the method of preparation of Al-bearing solutions can significantly affect the concentration of monometric Al species in solution. Because the procedures by which Al solution concentrations are measured in solubility studies determine the quantity of so-called monomeric species present, apparent differences in calculated gibbsite stability most likely arise from differences in experimental procedure rather than differences in crystallinity. A review of published solubility data for gibbsite suggests that the best values that can be currently estimated from that data for the Gibbs free energies of formation of Al(OH){sub 4}{sup {minus}} and Al{sup 3 +} are {minus}1305.0 {plus minus} 1.3 and {minus}489.8 {plus minus} 4.0 kJ/mol. Based on the value for the entropy and accepting the recommended Gibbs free energy for Al(OH){sub 4}{sup {minus}}, the authors have calculated the Gibbs free energy and enthalpy of formation of boehmite to be {minus}918.4 {plus minus} 2.1 and {minus}996.4 {plus minus} 2.2kJ/mol, respectively, from solubility data for boehmite.
- OSTI ID:
- 5669396
- Journal Information:
- American Mineralogist; (United States), Journal Name: American Mineralogist; (United States) Vol. 76:3-4; ISSN AMMIA; ISSN 0003-004X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
152002* -- Geothermal Data & Theory-- Properties of Minerals & Rocks
36 MATERIALS SCIENCE
360606 -- Other Materials-- Physical Properties-- (1992-)
ALUMINIUM 27
ALUMINIUM COMPOUNDS
ALUMINIUM HYDROXIDES
ALUMINIUM ISOTOPES
ALUMINIUM OXIDES
CHALCOGENIDES
COMPARATIVE EVALUATIONS
ENERGY
ENTHALPY
ENTROPY
EVALUATION
FORMATION FREE ENERGY
FREE ENERGY
GIBBSITE
HYDROGEN COMPOUNDS
HYDROXIDES
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
METAMORPHIC ROCKS
MINERALS
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHYSICAL PROPERTIES
RESONANCE
ROCKS
SAMPLE PREPARATION
SEDIMENTARY ROCKS
SOLUBILITY
SPECIFIC HEAT
STABLE ISOTOPES
THERMODYNAMIC PROPERTIES
VARIATIONS