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|Type:||Artigo de periódico|
|Title:||Speciation of aqueous chromium(VI) solutions with the aid of Q-mode factor analysis followed by oblique projection|
|Abstract:||The identities of the species of chromium(VI) that are present in aqueous solution, their spectra and their equilibria, continue to be a subject of discussion in the literature. In this paper, the composition of the Cr(VI) equilibria was estimated from the UV-vis spectra of dilute potassium dichromate solutions, without any prior knowledge of the quantities of pure components, with the aid of Imbrie Q-mode factor analysis (Q-mode FA) followed by Varimax rotation and Imbrie oblique projection. Combining these results with the k-matrix method, it was possible to obtain the spectra of the individual Cr(VI) species. Sets of 3.3 x 10(-4) and 3.3 x 10(-5) mol 1(-1) Cr(VI) solutions were studied. In the pH range from 1 to 12, two factors were identified, which were related to the two species, chromate ion (CrO42-) and bichromate ion (HCrO4-). When the analysis was extended to concentrated acid media, another factor appeared, which was related to chromic acid (H2CrO4). No evidence for the dichromate ion (Cr2O72-) was seen at the Cr(VI) concentrations used. The spectra of the pure components were obtained and pK values for the first and second chromic acid dissociations were estimated as -0.54 and 5.8, respectively. (C) 2000 Elsevier Science B.V. All rights reserved.|
Q-mode factor analysis
|Editor:||Elsevier Science Bv|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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