Invisible inks using iron (III) chloride

Invisible letterings show after adding a brown solution

Scientific name: Demonstration of the reactions of iron (III) chloride with potassium thiocyanate and potassium ferrocyanide

YouTube

Tinta invisible de KSCN

Невидимые чернила - жёлтая кровяная соль

by Aydar Galimov

Невидимые чернила - химический опыт для шпионов!

Safety

Wear lab gloves and eye protection.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

FeCl3 + 3 KSCN → Fe(SCN)3 + 3 KCl

4 FeCl3 + 3K4[Fe(CN)6] → Fe4[Fe(CN)6]3 + 12 KCl

Step-by-step instruction

  1. Dissolve some iron (III) chloride, potassium thiocyanate and potassium ferrocyanide separately in water.
  2. Write something on paper using potassium thiocyanate and potassium ferrocyanide solutions. Letterings are invisible.
  3. Soak the paper with iron (III) chloride solution using a sprayer. Letterings become visible.

Scientific background

Solutions of potassium thiocyanate and potassium ferrocyanide are colorless, and letterings made with these solutions are invisible.

Iron (III) chloride reacts with potassium thiocyanate forming red colored iron thiocyanate Fe(SCN)3.

Iron (III) chloride reacts with potassium ferrocyanide forming a deep blue precipitate of prussian blue Fe4[Fe(CN)6]3.

Danger:
Coolness:
Difficulty:

Published on 02 September 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst