This solution has been found useful in staining frozen sections for rapid diagnosis, and as a differential stain for secretion granules, following eosin.
When methylene blue is boiled with an alkali, the two dyes, methylene violet and methylene azur, and probably others, are formed by oxidation. Unna recognized that this change gradually takes place in old alkaline solutions of methylene blue, and he utilized the resulting "polychrome-methylene blue" for special staining purposes. These dyes in combination with eosin (Romanowsky stain and modifications), applied to cells and tissue with proper technic, afford a great deal of differentiation and pleasing contrast.
The following method has been devised for the staining of frozen sections fixed in liquor formaldehydi and for staining paraffin sections fixed in liquor formaldehydi, liquor formaldehydi-Zenker or alcohol after eosin staining.
An acid polychrome-methylene blue solution is made from methylene blue (Koch f. bac.), 1 gm.; potassium carbonate, 1 gm.,