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Reducing Rinses

Hotchkiss’ reducing rinse is applied to ensure any periodate or iodate remaining in the tissue from the oxidation step is removed. This may be done to ensure they do not recolour Schiff’s reagent and lead to false positive results.

The step is usually omitted in current practice, as washing for 5 minutes or so with tap water or 70% ethanol accomplishes much the same. It has also been shown that it may block some aldehydes and reduce the intensity of the reaction.


Potassium iodide1g
Sodium thiosulphate1g
Distilled water20mL
Ethanol, absolute30mL
Hydrochloric acid, 2N0.5mL


  1. Apply following periodic acid oxidation and prior to treating with Schiff’s reagent.
  2. Rinse with 70% ethanol.
  3. Place in the solution for 5 minutes
  4. Rinse with 70% ethanol.
  5. Continue on with the stain.


  1. Lillie, R.D., (1954)
    Histopathologic technique and practical histochemistry Ed.2
    Blakiston, New York, USA
  2. Pearse, A. G. E., (1968, 1972)
    Histochemistry: Theoretical and Applied, Ed. 3
    Churchill Livingstone, Edinburgh, London, UK