Lemon juice and iodine invisible inks

Message written with lemon juice appears when paper is treated with iodine solution.

Scientific name: Vitamin C prevents complex formation between iodine and starch.


Magic Writing

by Shelby Hoyert

невидимые чернила (лимонная кислота и йод)

by jesterolog7

невидимые чернила


Невидемые чернила

by Зарина Сунгатова

ШПИОНСКИЕ ЧЕРНИЛА - опыт с лимонной кислотой и йодом



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Reaction formula

(C6H10O5)n + I2 → I2*(C6H10O5)n

I2 + I- → I3-

C6H8O6 + I3- + H2O → C6H6O6 + 3I- + 2H+

Step-by-step instruction

  1. Take a paint brush and write a message with lemon juice.
  2. Prepare iodine solution in a petri dish. Pour a few milliliters of iodine tincture in a petri dish and dissolve it in water.
  3. Put the paper in the petri dish or coat it with iodine solution using a paint brush.
  4. The text will stay white while the rest of paper will turn blue.

Scientific background

In this experiment lemon juice developed by iodine solution is used to prepare invisible inks. When paper with written message is treated with iodine solution the starch contained in paper reacts with iodine to form a colored complex:

(C6H10O5)n + I2 → I2*(C6H10O5)n

The paper turns blue but the message still stays white. Lemon juice contains vitamin C which prevents the reaction between starch and iodine:

I2 + I- → I3-

C6H8O6 + I3- + H2O → C6H6O6 + 3I- + 2H+


Published on 23 March 2015

  • Fire
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  • Explosion
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  • Solution
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  • Color change
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