Color Changing Milk of Magnesia

Milk of Magnesia with universal indicator changes color when vinegar is added

Scientific name: Magnesium hydroxide neutralizes acetic acid from vinegar


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Avoid vinegar contact with eyes.

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

Reaction formula

CH3COOH + H2O → CH3COO- + H3O+

Mg(OH)2 + 2H3O+ → 4H2O + Mg2+

Step-by-step instruction

  1. Pour some water in a beaker and add some milk of magnesia (approximately in ratio 20 ml of MOM per 1 l of water).
  2. Add a few milliliters of universal indicator solution into the beaker. The solution becomes deep purple.
  3. Add some vinegar into the beaker. The liquid in the beaker quickly turns red and then gradually restores purple color.

Scientific background

Suspension of MOM has an alkaline pH. Because of this universal indicator has purple color. When vinegar was added, pH becomes acidic, and red color appears. Due to the neutralization reaction between the MOM and the vinegar, pH returns to an alkaline level.


Published on 10 March 2015

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