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Bauer Reaction for Carbohydrates

Bauer Reaction

for Carbohydrates



  • A Schiff reagent
  • A progressive hemalum, such as Mayer
  • Chromic acid
    Chromium trioxide4g
    Distilled water100mL
  • Sulfurous acid
    Sodium metabisulfite, 10% aqu.6mL
    Hydrochloric acid, 1N5mL
    Distilled water100mL

Tissue Sample

5µ paraffin sections of neutral buffered formalin fixed tissue are suitable. Other fixatives are likely to be satisfactory. Most trichrome stains benefit from picric acid or mercuric chloride fixation. Formalin fixed tissues may benefit from secondary fixation of sections in Bouin’s fluid.


  1. Bring sections to water via xylene and ethanol.
  2. Oxidize in chromic acid for 40-60 minutes.
  3. Rinse with tap, then distilled water.
  4. Place into Schiff’s reagent for 15 minutes.
  5. Place into sulfurous acid rinses, 3 changes of 2 minutes each.
  6. Wash with running tap water.
  7. Counterstain with hemalum for 1 minute, and blue
  8. Dehydrate with ethanols.
  9. Clear with xylene and mount with a resinous medium.

Expected Results

  • Glycogen, mucin  –  red
  • Fungi  –  red
  • Nuclei  –  blue


  • Modern practice is to leave out the sulfite rinses and wash with large amounts of tap water.
  • A progressive hemalum should be used as counterstain because regressive hemalums sometimes stain mucin.
  • Mucins are not usually as dark as with a PAS.
  • Applying chromic acid for too long weakens staining due to continued oxidation of the aldehydes first produced.

Safety Note

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


  1. McManus, J. F. A. and Mowry, R. W., (1960)
    Staining Methods Histologic and Histochemical
    Harper & Row, New York, NY, USA.