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Neutralising Antacids
AKA: Neutralisation of Indigestion Tablets


Antacid tablets are neutralised using acid and their effectiveness compared.


This practical involves students reacting hydrochloric acid with an indigestion tablet to achieve neutralisation. This can be conducted as an investigation into determining which type of tablet is most effective.

Equipment typically required (per set):

  • Burette, clamp and stand
  • Eye protection
  • Pestle and mortar
  • 250 cm3 conical flask
  • Methyl orange indicator
  • Hydrochloric acid (0.5 mol dm-3)
  • One indigestion tablet

Indigestion tablets are alkali when mixed with water and so are generally used to neutralise stomach acids. This practical can show which type of tablet neutralises acid most effectively and so a selection of antacid tablets may be required for comparison.

Students firstly crush a single antacid tablet using a pestle and mortar. The powder is poured into the conical flask and three drops of methyl orange indicator are added.

The flask is placed under the burette and whilst agitating the indicator and powder mixture, add 0.5cm3 of acid from the burette at intervals. As soon as the mixture in the conical flask turns red and stays red for 60 seconds, maximum neutralisation has occurred.

The amount of acid used is usually calculated and compared against neutralisation of other types of tablet. Students can then work out which type would be most effective against excess acid in the stomach.



Wear eye protection.

The contents of this page are for information only. Please refer to CLEAPSS, SSERC or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.