Fake chemical cut
How to make artificial blood
Oh, no! You slipped and cut your hand on a plastic knife! Wait, what…?
Do not try it at home! Perform this experiment only under professional supervision.
Equipment and reagents
- iron(III) chloride;
- potassium thiocyanate;
- sodium fluoride;
- plastic knife;
- cotton wool;
Prepare solutions of iron(III) chloride, potassium thiocyanate, and sodium fluoride by dissolving the respective reagents in water. Soak a cotton ball in the solution of potassium thiocyanate, then rub the cotton ball on your hand. Dip a plastic knife in the solution of iron(III) chloride and draw it gently across your palm. This creates a bloody “cut” on your hand! Treat it by wiping a cotton swab dipped in the sodium fluoride solution across the “wound.” Your hand is safe and sound!
Naturally, there was never any blood on your hand. What you observed was a chemical reaction that occurs between the solutions of potassium thiocyanate and iron(III) chloride. Thiocyanate ions and ferric ions form complex, blood-red compounds, the most well-known of which being iron(III) thiocyanate:
FeCl₃ + 3KSCN=Fe(CNS)₃ + 3KCl
Adding sodium fluoride destroys the iron(III) thiocyanate complexes, and colorless hexafluoroferrate(III) [FeF₆]³¯ ions form.
Fe(CNS)₃ + 6NaF=Na₃[FeF₆] + 3NaCNS