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Pseudo-Periodic Acid Schiff


Pseudo-Periodic Acid Schiff


The terms Pseudo-Schiff and Pseudo-PAS refer to the use of dyes other than pararosanilin or basic fuchsin to make a Schiff type solution and use it for demonstrating carbohydrates. While an interesting exercise, it has little practical use except for the occasional demonstration of fungi with a fluorescent pseudo-Schiff solution made with acriflavine. The following dyes, among others, have been suggested.

DyeCI NumberColor
Acid fuchsin42685violet
Azure A52005blue
Azure C52005blue
Crystal violet42555blue-violet
Methyl violet42535violet
Methylene blue52015blue
Safranin O50240red
Toluidine blue52040blue


  • 1% hydrochloric acid in 70% ethanol
  • A suitable counterstain

Preparation of Pseudo-Schiff Solution

Prepare a solution according to the instructions for acriflavine Schiff reagent, or another formula, if preferred. Note that they will likely not become colourless, so leave for 48 hours, then filter the solution and store refrigerated.

Tissue Sample

5 µ paraffin sections of neutral buffered formalin fixed tissue are suitable. Other fixatives are usually satisfactory, although glutaraldehyde should be avoided.


  1. Bring sections to water via xylene and ethanol.
  2. Place into periodic acid for 10 minutes.
  3. Wash with running water.
  4. Rinse with distilled water.
  5. Place in pseudo-Schiff’s reagent for 10-30 minutes.
  6. Rinse with distilled water.
  7. Place in acid ethanol for 5 minutes.
  8. Wash well with tap water for about 10 minutes.
  9. Counterstain with a suitable contrasting nuclear stain.
  10. Dehydrate with ethanol, clear with xylene and coverslip using a resinous medium.

Expected Results

  • Oxidisable carbohydrates – coloured according to the dye used
  • Nuclei – as stained

Safety Note

Prior to handling any chemical, consult the Safety Data Sheet (SDS) for proper handling and safety precautions.


  1. Culling C.F.A., (1963)
    Handbook of histopathological and histochemical techniques Ed. 2
    Butterworth, London, UK.