Multiple choice

Which of the following substances can be used in making disappearing ink?

  1. Phenolphthalein

  2. Thymolphthalein

  3. Rose Bengal

  4. Green S

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Thymolphthalein is an acid-base (pH) indicator. Its transition range is at approximately pH 9.3-10.5. Below this pH, it is colorless; above this pH, it is blue. The molar extinction coefficient for the blue thymolphthalein dianion is 38000 M-1cm-1 at 595 nm.It can be used to make a disappearing ink