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This procedure is also called saponification. It reverses the effects of acetylation and restores PAS positivity. However, this is not absolute, and proceeds at different rates for different compounds. It may therefore be used to identify compounds based on double criteria: A) blocking of staining by acetylation, and B) restoration of staining by deacetylation.


Ethanol, absolute30mL
Distilled water10mL
Ammonia water, 28%10mL


  1. Celloidinise previously acetylated sections.
  2. Place into the solution in a sealed container at 37°C for 4-24 hours.
  3. Rinse well with 80% ethanol.
  4. Continue on with the staining method.
Glycogen37°C4-6 hoursRestored
Intestinal mucins37°C4-6 hoursRestored
Basement membrane37°C16 hoursRestored
Brush borders37°C16 hoursRestored
Retinal rods37°C24 hoursRestored


  1. Lillie, R.D., (1954)
    Histopathologic technique and practical histochemistry Ed.2
    Blakiston, New York, USA