Bleaching is a process by which a chemical reaction results in the perceived removal of color. In this project we wanted to see whether it would be practical to determine the rate of indigo bleaching using reflectance instead of the more typical absorbance. If practical, then it would be possible to measure the kinetics of bleaching while watching the process occur, unlike in absorbance where the cuvette is obscured by the spectrometer during the bleaching process. We used blue jeans as our bleaching target. When denim is bleached, indigo dye is decolonized through oxidation by the hypochlorite ion in bleach. Rate laws for indigo oxidation were compared for both reflectance and absorbance. This experiment can easily be coupled to the synthesis of indigo for either a two- or one-semester organic chemistry laboratory using both rate law determinations.

Kinetics of indigo bleaching: Reflectance versus absorbance

251st National Meeting (2016)

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