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Galassi’s Schiff Reagent

Galassi’s Formulation

Solution

MaterialVariation 1
Amount
Variation 2
Amount
Pararosanilin chloride2.5g2.5g
Distilled water200mL
Sulfur dioxide gasGas cylinder
Sulfurous acid (1M)100mL
Sulfuric acid (1M)4mL4mL
Activated charcoal (powder)1g1g

Preparation

  1. Variation 1: Dissolve the pararosanilin into 100 mL distilled water. In a fume hood, slowly bubble sulfur dioxide gas through the solution until it becomes translucent.
    Variation 2: Dissolve the pararosanilin into 100 mL sulfurous acid.
  2. Stopper well and store in the dark for one to two days.
  3. If not water clear, add activated charcoal, shake for a minute and filter.
  4. If it is still not water clear, repeat the treatment with sulfur dioxide (var 1).
  5. Add the sulphuric acid.
  6. Leave unstoppered and place in a cool fume hood for a couple of days.
  7. If the solution develops a pink color, stopper and continue.
  8. Filter out the crystals.
  9. Wash the crystals with hydrochloric acid ethanol.
  10. Dry the crystals overnight over silica gel.
  11. A good sample of pararosaniline should yield over 2 grams of crystals.

Working Solution

  1. Dissolve 0.2 grams of the crystals in 100 milliliters of 0.1N hydrochloric acid.
  2. Stir well and use gentle heat if necessary.

Notes

  • Make sure that when you bubble the sulfur dioxide through the pararosanin solution you are doing so either under a fume hood, or outside at an elevation that stops anyone else from smelling it. Sulfur dioxide not only stinks, but it can also be dangerous in heavy doses. Bubble the gas slowly through the solution until it begins to change color, then stopper and place in the dark.
  • Store the crystals at 0-5°C in a tightly stoppered bottle, protected from moisture.
  • This solution may be used to replace any other Schiff’s reagent, but will produce a standard and reproducible degree of coloration.

Safety Note

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

References

  1. Galassi, L., (1993).
    A simple procedure for crystallization of the Schiff Reagent.
    Biotechnic & Histochemistry, v. 68, p. 175.