The Gibbs Free Energy of the Formation of the Al(OH)4− Ion at Elevated Temperatures

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Abstract
The Gibbs free energy of the formation of the Al(OH)4− ion, ΔGf°[Al(OH)4−], has been determined from the solubility data of alumina hydrates at temperatures up to 300 °C. According to the results of thermodynamical calculations, ΔGf°[Al(OH)4−] is −1305.3 kJ/mol at 25 °C, and it decreases almost linearly with an increase in the temperature. Its temperature dependence between 25 and 300 °C can be expressed as follows: ΔGf°[Al(OH)4−]=−1152.7–3.318T−5.64×10−4T2+1.202TlogT.