Equilibrium and structural studies of silicon(IV) and aluminium(III) in aqueous solution. 12. A potentiometric and 29Si-NMR study of silicon tropolonates |
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Authors: | Staffan Sjöberg Nils Ingri Ann-Marie Nenner Lars-Olof Öhman |
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Affiliation: | Department of Inorganic Chemistry, University of Ume», Sweden |
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Abstract: | Complexation in the H+-Si(OH)4-tropolone (HL) system was studied in 0.6 M (Na)Cl medium at 25° C. Speciation and formation constants were determined from potentiometric (glass electrode) and 29Si-NMR data. Experimental data cover the ranges 1.5 ? - log[H+] ? 8.4, 0.002 ? B ? 0.012 M, and 0 ? C ? 0.060 M (B and C stand for the total concentration of Si and tropolone, respectively). In acid solutions (-log[H+] ? 3) a hexacoordinated cationic complex, SiL3+, is formed with log K(Si(OH)4 + 3HL + H+ XXX SiL3+ + 4H2O) = 7.08 ± 0.03. Furthermore, the formation of a disilicic acid was established from 29Si-NMR data. The dimerization constant of Si(OH)4 was found to be 10 exp (1.2 ± 0.1). In model calculations the solubility of quartz and amorphous SiO2 in the presence of tropolone is demonstrated. Data were analyzed using the least-squares computer program LETAGROPVRID. |
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Keywords: | Address reprint requests to Dr. S. Sjöberg Department of Inorganic Chemistry University of Umea S-901 87 Umea Sweden. |
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