We have adapted this experiment to use methyl red as the substrate for photolysis. Methyl red will be available in virtually any chemistry stockroom, is compatible with aqueous chemistry, and gives excellent results with this experiment. Our students carried out the photolysis in a UV photoreactor, which makes it possible to nearly destroy the methyl red within 30 minutes in the presence of TiO₂, starting with a concentration of around 3 × 10^–5 M methyl red. We filtered the samples for absorbance measurement using 4.5 µm HPLC filters and monitored the absorbance at 520 nm. A sample data set is shown in Figure 1.

Figure 1. Concentration of methyl red solution in UV photoreactor, with and without TiO₂ catalyst.

Literature Cited

1. Herrera-Melián, J. A.; Doña-Rodriguez, J. M.; Tello Rendón, E.; A. Soler Vila; Brunet Quetglas, M.; Alvera Azcárate, A.; Pascual Pariente, L. J. Chem. Educ. 2001, 78, 775–777.

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