Part I: Visual inspection of dye bleaching reactions

There are 4 cuvettes: A (peroxide and catalyst), B (peroxide and no catalyst), C (bleach and catalyst), D (bleach and no catalyst). After oxidant is added to each using a syringe, a timer starts. The solutions start to lose color. When the timer reaches 5 minutes, cuvette C is almost colorless, cuvette D is very faintly red, cuvette A is faintly red, and cuvette B has slightly lost its initial color.

Visual inspection

Materials needed: Red #40 stock solution, phosphate buffer, Fe-TAML, water, peroxide, bleach, cuvettes, syringes, glass stirring rods, timer

1. Prepare the following 4 cuvettes:

2. Prepare two plastic syringes, each containing 0.50 mL of peroxide solution.

3. As simultaneously as possible, start a timer (stopwatch) and add the peroxide to cuvettes A and B. As quickly as possible, use the glass stirring rods to mix each solution for 2-3 seconds, then set the stirring rods aside. Monitor the timing and character of any color changes you observe. If color remains after 5 minutes, note “greater than 5 min” in your notebook, but set the cuvette aside and move onto the next step. You can periodically look back to see if it changes over longer amounts of time.

4. Repeat the above operation using cuvettes C and D, using bleach instead of peroxide. Again, do not spend more than 5 minutes on this step.

Go back to part I intro

Continue to part II

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