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Kinetic Dye Degradation measuring Absorbance & Transmittance using a Cuvette Holder

Posted on: August 25th, 2022

Allura Red is a red powdered azo dye that is used in food, cosmetic, drug, textile, and, paper industries. Allura Red is known by many names, but the most familiar probably being Red 40 or E129. Azo dyes are synthetic coloring agents that contain an azo group (-N=N-) in their chemical structure.

Kinetics is the study of how quickly, or slowly, a chemical reaction occurs. This experiment applies kinetics to dye degradation. For the oxidizing agent, we used bleach to degrade the color of Allura Red. The active ingredient in bleach is sodium hypochlorite (NaClO). The sodium hypochlorite changes the chemical compound of Allura Red causing the red color to disappear.

In this experiment, we measured the absorbance and transmittance of an Allura Red solution mixed with a bleach solution. Allura Red absorbs green coloring (480- 560nm) and transmits red coloring (640-700 nm). Using Beer-Lambert’s Law, we used the absorption measurement conversions to solve for the unknown changing concentrations of Allura Red.

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