Dehydrate with ethanol, clear with xylene and mount with a resinous medium.
Fungi – blue
Nuclei – red
Background – pink
It is well known that metallic azides can be explosive.
However, thiosemicarbazide is not a simple metallic azide.
The MSDS from J. T. Baker (via the SIRI database) says:
Flash Point: N/A
Lower Explosive Limit: N/A
Upper Explosive Limit: N/A
Unusal Fire and Expl.rds: NONE IDENTIFIED
Thiosemicarbazide has the formula H2NNHCSNH2.
The hydrazine group (H2NNH-) combines with any aldehydes
generated by periodic acid oxidation. The thiocarbamyl group
(-CSNH2) is a more powerful reducing agent than are
aldehydes, and rapidly reduces ferricyanide to ferrocyanide,
which immediately forms a prussian blue deposit at the site.
The mallory bleach lightens background staining and improves
contrast. It may also produce some aldehyde which is removed
in step 6.
The oxidation-aldehyde block-reoxidation sequence removes most
oxidisable carbohydrate other than fungi, and improves contrast.
The Schmorl's solution is Lillie's modification.
Reference Hayashi, I., Tome, Y. and Shimosato, Y., (1989) Thiosemicarbazide used after periodic acid makes methenamine silver staining of renal glomerular basement membranes faster and cleaner.
Stain Technology, v 64, p 185.
Lillie, R.D. and Glenner, G. G. (1957)
Journal of Histochemistry and cytochemistry. v 5, p. 311
Llewellyn, B. D., (2014) Thiosemicarbazide-ferricyanide reduction for the histochemical demonstration of aldehydes in tissue sections.
Biotechnic & Histochemistry, v 89, p 228-31.