Principle
Pyrogallol absorbs oxygen in the presence of alkali. The test demonstrates the presence or absence of oxygen.
Procedure
- Pyrogallol solution is mixed with sodium hydroxide (alkali).
- The mixture is exposed to the gas sample.
- If oxygen is present, pyrogallol absorbs oxygen and turns brown.
Medicolegal Use — Detection of Pneumothorax
Used during autopsy to determine whether air is present in the pleural cavity.
Method in pneumothorax:
- The thoracic cavity is opened under water.
- Escaping gas is collected.
- Gas is exposed to alkaline pyrogallol solution.
- Absorption of oxygen indicates atmospheric air.