The Free Energy of Formation of Gibbsite and Al(OH)4- from Solubility Measurements1
- 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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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