Enthalpies of formation of low albite (NaAlSi3O8), gibbsite (Al(OH)3), and NaAlO2; revised values for ΔH°f,298 and ΔG°f,298 of some aluminosilicate minerals

Journal of Research of the U.S. Geological Survey
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Abstract

The enthalpies of formation from the elements ΔH°t, of low albite, analbite, NaAlSi3O8 glass, gibbsite (Al(OH)3), and NaAlO2, have been determined by hydrofluoric acid solution calorimetry from measurements of the heats of solution, ΔH°soln, of low albite, NaAlO2, SiO2, Al(OH)3, Al, H2O, NaCl, and HC1-12.731H2O in 20.1 weight percent HF(aq) at temperatures between 303.15 and 348.15 K. At 298.15 K the enthalpies of formation, ΔH°f,298, for low albite, analbite, NaAlSi3O8 glass, gibbsite (Al(OH)3), and NaAlO2 are -3 935 115±3415, -3 924 235±3640, -3 875 455±3700, ±1293130±1190, and 1135 990±1255 J mol-1, respectively. Our values for the enthalpies of formation of low albite, analbite, and for NaAlSi3O8 glass are approximately 13 810 J mol-1 more negative than the values calculated by D. R. Waldbaum in 1968. Our value for the enthalpy of formation of gibbsite at 298.15 K is 11234 J more negative than the value of R. Barany and K. K. Kelley obtained in 1961. The standard Gibbs free energies of formation, ΔG°f,298 for low albite, analbite, and gibbsite calculated from the above enthalpies and the appropriate entropy data are -3 711 715±3435, -3 706 500±3660, and -1154 890±1200 J mol-1, respectively. The enthalpy of solution of Standard Reference Material 1654, α-quartz (37 to 74 μm), in 20.1 wt percent HF(aq) is -137 737±209 J mol-1 at 333.15 K. This value is approximately 1255 J less negative than the value obtained by King in 1951 and 1952 for material that has a mean particle diameter of less than 5 μm and that has been used by the U.S. Bureau of Mines in their determinations of the enthalpies of formation of many silicates. Revised values of the enthalpies and Gibbs free energies of formation are presented for some aluminosilicate minerals, based upon this new data for ΔH°f,298 of gibbsite and the heat of solution of α-quartz.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Enthalpies of formation of low albite (NaAlSi3O8), gibbsite (Al(OH)3), and NaAlO2; revised values for ΔH°f,298 and ΔG°f,298 of some aluminosilicate minerals
Series title Journal of Research of the U.S. Geological Survey
Volume 5
Issue 4
Year Published 1977
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Description 17 p.
First page 413
Last page 429
Online Only (Y/N) N
Additional Online Files (Y/N) N
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