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This article in SSSAJ

  1. Vol. 30 No. 5, p. 595-598
    Received: Mar 21, 1966
    Accepted: June 16, 1966

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The Free Energy of Formation of Gibbsite and Al(OH)4- from Solubility Measurements1

  1. J. A. Kittrick2



Solubility determinations on two particle sizes of crystalline gibbsite, from both undersaturation and supersaturation in the acid pH range, gave a KSO of −34.03 ± 0.05. Using the same gibbsite in the alkaline pH range and extrapolating values from supersaturation to infinite time, a *KS4 of −15.30 ± 0.05 was obtained. From these values a ΔGf0 (gibbsite) of −274.20 ± 0.06 kcal/mole of Al(OH)3 and a ΔGf0 [Al(OH)4- aq] of −310.03 ± 0.07 kcal/mole were calculated. The value for gibbsite confirms previous work on the stability of gibbsite and the new Al(OH)4- value eliminates a discrepancy between gibbsite stabilities derived from solubility measurements in the acid and in the alkaline pH range.

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