Galassi's Schiff Reagent

Schiff reagent

Ingredient Var 1 Var 2
Pararosanilin chloride 2.5 g 2.5 g
Distilled water 100 mL
Sulphur dioxide gas cylinder
Sulphurous acid (1M) 100 mL
Sulphuric acid (1M) 4 mL 4 mL
Activated charcoal (powder) 1 g 1 g

Hydrochloric ethanol

Ingredient Amount
Ethanol, 100% 25 mL
Hydrochloric acid (0.1N) 25 mL


Var 1
Dissolve the pararosanilin into 100 mL distilled water.
In a fume hood, slowly bubble sulphur dioxide gas through the solution until it becomes translucent.

Var 2
Dissolve the pararosanilin into 100 mL sulphurous acid.

Stopper well and store in the dark for one to two days.
If not water clear, add activated charcoal, shake for a minute and filter.
If it is still not water clear, repeat the treatment with sulphur dioxide (var 1).
Add the sulphuric acid.
Leave unstoppered and place in a cool fume hood for a couple of days.
If the solution developes a pink colour, stopper and continue.
Filter out the crystals.
Wash the crystals with hydrochloric acid ethanol.
Dry the crystals overnight over silica gel.
A good sample of pararosaniline should yield over 2 grams of crystals.

Working solution
Dissolve 0.2 grams of the crystals in 100 millilitres of 0.1N hydrochloric acid.
Stir well and use gentle heat if necessary.


  1. Make sure that when you bubble the sulphur 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. Sulphur dioxide not only stinks, it can be dangerous in heavy doses. Bubble the gas slowly through the solution until it begins to change colour, then stopper and place in the dark.
  2. Store the crystals at 0-5°C in a tightly stoppered bottle, protected from moisture.
  3. This solution may be used to replace any other Schiff's reagent, but will produce a standard and reproducible degree of colouration.


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




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