What are some novel ways to use indicators (besides titrations)?

  1. Mood lipstick. Acid-base indicators in the cosmetics change color on application due to skin pH.
  2. Turning "water" to "wine". Add phenolpthalein to a clear dilute NaOH solution.)
  3. Making real wines red. Red wines contain anthocyanins, which are pH indicators. Adjusting the pH of the wine changes its color (and its taste). Welch's grape juice works, too.
  4. Disappearing ink and invisible ink Write a message in colorless phenolthalein. Spray the paper with a dilute NaOH solution and the letters appear in pink.
  5. Demonstrating how an ion exchange column works (see the July 1996 issue of the Journal of Chemical Education for more).
  6. Food coloring
  7. Monitoring swimming pool pH.
  8. Soil pH kits.
  9. Demonstrating the electrolysis of water
  10. Making a "voice activated" chemical reaction. (a solution of phenol red in very slightly alkaline water will turn from red to yellow, if you talk to it for a while :) Carbon dioxide from your breath neutralizes the solution and causes the color change. The recipe can be found in L. R. Summerlin and J. L. Ealy's Chemical Demonstrations, v. 1, p. 40 (ACS Press, 1985).

Author: Fred Senese senese@antoine.frostburg.edu

General Chemistry Online! What are some novel ways to use indicators (besides titrations)?

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