Aluminum-Tannin Equilibria: A Potentiometric Study
- 1 January 1987
- journal article
- research article
- Published by CSIRO Publishing in Australian Journal of Chemistry
- Vol. 40 (12) , 2015-2022
- https://doi.org/10.1071/ch9872015
Abstract
The equilibrium reactions between aluminium(III) and an epicatechin polymer or tannin (T) have been studied by potentiometric titration at 25ºC, I = 0.001 M. The tannin, which has on average ten 1,2-dihydroxybenzene units per molecule, encapsulates the aluminium ion to form a bis(l,2-diphenolato) complex at pH 5-7. Stability constants are reported for Al(TH-2) (logK11-2, -3.95 ± 0.05), Al(TH-3) (logK11-3, -4.5 ± 0.1) and Al(TH-4) (logKl1-4, -5.7 ± 0.2). A small chelate effect arising from coordination of remote pairs of 1,2-diphenolato groups was observed.Keywords
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