Activities | Chemistry and Biotechnology
The devil's blood
- Ammonium hydroxide (liquid)
- Phenolphthalein (found in chemical analysis laboratories)
- Alcohol (common alcohol used in household cleaners)
1. Preparation of the indicator: Mix 40 ml of phenolphthalein with 70 ml of alcohol. This solution is called an indicator because it turns red in alkaline media and neutral in acidic media;
2. In another bowl mix together 170 ml of water and 100 ml of ammonium hydroxide;
3. Add the indicator gradually in the container containing ammonium hydroxide solution. What happens? The colour will change. If you want a more reddish solution, add more phenolphthalein solution.
4. Your "Devil's Blood" is ready. And now it's just fun!
Why does the solution turn red? Because the medium that contains NH3 is alkaline.
The product used for colouring (staining) fabric is actually a base (ammonium hydroxide) that turns red in the presence of an indicator. This substance is unstable and decomposes rapidly in ammonia and water; ammonia is a gas that evaporates very quickly at room temperature, making the fabric return back to its original colour.
Activity instructors: Isabel Silva, Sofia Duarte (Lab.EQ - Chemical Engineering Lab)