Enthalpies of formation of low albite (NaAlSi/sub 3/O/sub 8/), gibbsite (Al(OH)/sub 3/), and NaAlO/sub 2/; revised values for. delta. H/sub f 298//sup 0/ and. delta. G/sub f 298//sup 0/ of some aluminosilicate minerals

Journal Article · Sat Jan 01 00:00:00 EST 1977 · J. Res. U.S. Geol. Surv.; (United States)

OSTI ID:5012104

Hemingway, B S; Robie, R A

The enthalpies of formation from the elements DELTA H/sup 0//sub t/, of low albite, analbite, NaAlSi/sub 3/O/sub 8/ glass, gibbsite (Al(OH)/sub 3/), and NaAlO/sub 2/, were determined by hydrofluoric acid solution calorimetry from measurements of the heats of solution, DELTA H/sub soln/ of low albite, NaAlO/sub 2/, SiO/sub 2/ Al(OH)/sub 3/, Al, H/sub 2/O, NaCl, and HCl . 12.731H/sub 2/O in 20.1 weight percent HF(aq) at temperatures between 303.15 and 348.15 K. At 298.15 K the enthalpies of formation, DELTA H/sup 0//sub f,298/, for low albite, analybite, NaAlSi/sub 3/O/sub 8/ glass, gibbsite (Al(OH)/sub 3/), and NaAlO/sub 2/ are -3,935,115 +- 3415, -3,924,235 +- 3640, -3,875,455 +- 3700, +-1,293,130 +- 1190, and 1,135,990 +- 1255 J mol/sup -1/, respectively. Our values for the enthalpies of formation of low albite, analbite, and for NaAlSi/sub 3/O/sub 8/ glass are approximately 13,810 J mol/sup -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 11,234 J more negative than the value of R. Barany and K. K. Kelley obtained in 1961. The standard Gibbs free energies of formation DELTA g/sup 0//sub g,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 -1,154,890 +- 1200 J mol/sup -1/, respectively. The enthalpy of solution of Standard Reference Material 1654, ..cap alpha..-quartz (37 to 74 ..mu..m), in 20.1 wt % HF(aq) is -137,737 +- 209 J mol/sup -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 ..mu..m 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 DELTA H/sup 0//sub f,298/ of gibbsite and the heat of solution of ..cap alpha..-quartz.

• Research Organization: Geological Survey, Reston, VA
• OSTI ID: 5012104
• Journal Information: J. Res. U.S. Geol. Surv.; (United States), Vol. 5:4
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
ALBITE
FORMATION FREE ENTHALPY
ALUMINIUM OXIDES
GIBBSITE
SODIUM OXIDES
ALUMINIUM SILICATES
CALORIMETRY
FORMATION HEAT
GLASS
HYDROFLUORIC ACID
SODIUM SILICATES
SOLUTION HEAT
ALKALI METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM HYDROXIDES
CHALCOGENIDES
ENERGY
ENTHALPY
FELDSPARS
FREE ENTHALPY
HYDROGEN COMPOUNDS
HYDROXIDES
INORGANIC ACIDS
MINERALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
REACTION HEAT
SILICATES
SILICON COMPOUNDS
SODIUM COMPOUNDS
THERMODYNAMIC PROPERTIES
152002* - Geothermal Data & Theory- Properties of Minerals & Rocks