Introduction

Household bleach reacts with a solution of green food coloring to first oxidize the yellow component of the dye, leaving only the blue coloring. Eventually, the blue dye is also oxidized, and the solution turns colorless.

To Conduct Demonstration:

  1. A dilute solution of green food coloring (about 1 drop / 50 mL) is prepared and placed (20 mL each) in three different 50 mL beakers.
  2. Solutions of bleach (10 mL) are added simultaneously to two of the beakers, reserving the third as a control: 
    • The more concentrated solution contains 2 mL of bleach in 10 mL of solution.
    • The dilute bleach solution has one drop of bleach in 10 mL. 
  3. After a few seconds, the disappearance of yellow dye with the more concentrated bleach solution can be observed, followed after several seconds by the more dilute bleach reaction.
  4. Complete colorlessness should occur after about 30 minutes with the more concentrated bleach solution. The less concentrated solution will probably remain blue.

The authors of the original paper were unsure of the specific reactions involved. Green food coloring is a mixture of FD&C Blue #1 and FD&C Yellow #5. The reactions presumably involve some sort of oxidation of the conjugated systems of both dyes.

Safety and disposal:

Goggles should be worn to protect from the bleach; solutions may be sink-disposed.