Solubility Products of Aluminum Hydroxide in Various Ionic Solutions

Abstract

Solubility products of AI(OH), were determined in various solutions of NH4+, Li+, N a + , K + , and Cazf ions. Increasing amounts of these hydroxides were added to the respective chloride solutions containing aluminum chloride. The solutions were aged for 3 months. Activities of the OH-ions were calculated from the p H values of the solutions. The total Al concentrations remaining in solutions were determined by Hsu's modified aluminon method. The A13 + ion concentrations were computed using the hydrolysis equilibria of Aveston. The ion product, aA,3+(a0,,-)3, was found to vary linearly with the [OH]/[AI] ratio. The solubility product of AI(OH)3 was obtained by extrapolating this ratio to 3. The pK,, values thus obtained were 30.55, 33.15, 30.75, 30.36, and 31.00 in NH4+, Li+, Na+, K + , and CaZ+ systems respectively. The anomalously low solubility product of AI(OH)3 in the Li+ system was attributed to the specific "lithium effect".

Chemical trigger toward phase separation in the aqueous Al(III) system revealed

“…The critical IAP for phase separation is [Al 3+ ]•[OH − ] 3 ≈ 1.57•10 −32 M 2 . This value essentially agrees with the solubility product of aluminum hydroxide, K sp ≈ 31.8 (23), suggesting that we, indeed, identify the moment of phase separation. (25).…”

NMR Crystallography Reveals Carbonate Induced Al‐Ordering in ZnAl Layered Double Hydroxide

“…The slightly higher Al content of the LDH85 solid as compared to LDH100 and LDH125 is attributed to co-precipitation of amorphous Al(OH) 3 phases exhibiting a much lesser solubility at lower pH as compared to Zn(OH) 2 . [20,23,24] The high order and strict ratio of Zn/Al of 2 manifests in unit cells with lower symmetry than R-3 m (see below). Nonetheless, in the found monoclinic unit cells the average metalmetal distances, which correspond to 1/3 of the b-lattice constants, are in full accordance of a Zn/Al ratio of 2/1 for LDH125 and LDH100 (Table 1).…”

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“…However, if, as Saeed and Lee have claimed, the pH is 2.92 in this surface layer, then the hydroxide concentration is insufficient to form Al(OH) 3 . The solubility product of Al(OH) 3 has been reported (Chen, 1973) to range from 10 -30 to 10 -34 (with a narrower range in the presence of 0.1 M supporting electrolyte, [1.0 -4.4] x 10 -31 ). Many sources cite a value of 2(10 -33 ), and this seems reasonable.…”