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Merck

A simple procedure for crystallization of the Schiff reagent.

Biotechnic & histochemistry : official publication of the Biological Stain Commission (1993-05-01)
L Galassi
ABSTRACT

Formation of crystals in Schiff reagents prepared from SO2 gas previously has been reported either soon after preparation, using high dye concentrations and heating, or after long periods of storage at room temperature. With the first type of procedure only a low yield of crystals accompanied by dye precipitation was obtained. Crystallization without dye precipitation took place if the reagent, prepared with pararosaniline base or chloride in a saturated SO2 solution, was stored for a sufficient time at room temperature in partly filled flasks. These crystals remained colorless if washed with acid alcohol after being separated by filtration. Schiff reagents layered with paraffin oil or supplemented with 0.1 M hydroquinone took much longer to crystallize, suggesting that crystallization is promoted by the partial oxidation of sulfurous acid to sulfuric acid. A high yield of crystals can be obtained at room temperature after as little as 24 hr by adding 0.04 M of H2SO4 to a Schiff reagent prepared with 2% pararosaniline chloride in a saturated SO2 solution. A Schiff reagent prepared with only 0.2% of these crystals gives an intense staining in the Feulgen and in the Periodic acid-Schiff reactions.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Pararosaniline acetate, Dye content 90 %
Sigma-Aldrich
Basic Fuchsin, Dye content >85 %
Sigma-Aldrich
Basic Fuchsin, certified by the Biological Stain Commission, Dye content ≥88 %
Sigma-Aldrich
Pararosaniline hydrochloride, >85.0% (HPLC)