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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/5416

Title: Reduction of potassium chromate by tannins
Authors: ARAKAWA, H
WATANABE, N
TAMURA, R
RAO, CP
Keywords: withered oak leaves
water-extracts
d-fructose
d-glucose
chromium(vi)
acid
constituents
glutathione
complexes
cr(vi)
Issue Date: 1998
Publisher: CHEMICAL SOC JAPAN
Citation: BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 71(8), 1993-1998
Abstract: The reduction of potassium chromate has been carried out with several tannin substances, including gallic acid, pyrogallol, ethyl gallate, polygalloylglucose, and withered oak-leaf tannin. Each reaction was followed by colorimetry, EPR spectroscopy, electrochemistry, and molecular-sieve chromatography. The progress of the chromate reductions was monitored by measuring the VIS and EPR spectra as a function of time. The observed pseudo-first-order reaction rate constants for Cr(III) formation were derived based on the intensities of the Cr(III) signals of the EPR spectra. Cyclic voltammograms of the simple reductants and their final Cr(III)-containing products formed from the reductions of chromate have also been measured. The formation of Cr(III)-tannin complexes was indicated by separation on a Sephadex G-25 column. The results obtained from VIS, EPR, and cyclic voltammetry were found to be mutually dependent, and showed close correlations among the data. The rate of reduction for Cr(VI) revealed the following trend: gallic acid > pyrogallol > ethyl gallate > polygalloylglucose > withered oak-leaf tannin. The results obtained in the present study suggest that the rates of reduction for Cr(VT) in the tannins depend upon their peak oxidation potentials and stabilities for Cr(III)-tannin complexes.
URI: http://dx.doi.org/10.1246/bcsj.71.1993
http://dspace.library.iitb.ac.in/xmlui/handle/10054/5416
http://hdl.handle.net/10054/5416
ISSN: 0009-2673
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