Alum from soda cans

Obtaining alum from soda cans


Alum from Soda Cans

by mrhomescientist


Wear lab goggles and gloves. Avoid the contact of sulfuric acid with skin.

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

Reaction formula

2 Al + 6 H2O + KOH → 2 KAl(OH)4 + 3 H2

2 KAl(OH)4 + H2SO4 → 2 Al(OH)3 + 2 H2O + K2SO4

2 Al(OH)3 + 3 H2SO4 → 2 Al3+ + 3 SO42- + 6 H2O

Step-by-step instruction

WARNING! This experiment is dangerous! You should NOT perform this at home. ONLY carry out this experiment, if you are a trained chemist, and you understand local safety and legal requirements, which are required to perform such experiments

  1. Put about 30 g of potassium hydroxide into a beaker.
  2. Dissolve potassium hydroxide in about 200 ml of water.
  3. Cut an aluminum can to pieces and put them into the potassium hydroxide solution.
  4. When the can is dissolved in the potassium hydroxide solution, filter the solution.
  5. Slowly add about 52.5 ml of concentrated sulfuric acid to the obtained solution. (A lot of heat is produced in this process, be careful!)
  6. Add 200 ml of water and heat the solution at stirring.
  7. Cool down and evaporate solution during a few days. Crystals of alum are formed.

Scientific background

In the first step of this synthesis aluminum from the can reacts with potassium hydroxide forming potassium aluminate KAl(OH)4. After addition of sulfuric acid potassium sulfate and aluminum hydroxide are formed. Than aluminum hydroxide reacts with sulfuric acid in presence of potassium ions (from potassium sulfate). Thus, potassium aluminum sulfate (potassium alum) is formed.


Published on 22 September 2015

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