Periodic Acid-SchifJ (PAS) Reaction 299 



fixation: any general fixative, but if glycogen or other soluble polysac- 

 charides are to be demonstrated, fixation and washing should be done 

 in alcoholic fluids of no less than 70% alcoholic content. 



A. Solutions (alcoholic): 

 Periodic acid: 



periodic acid, HIO4 0.8 gm. 



distilled water 30.0 ml. 



sodium acetate, hydrated 0.27 gm. 



(or 10 ml. M/5 sodium acetate) 

 absolute ethyl alcohol 70.0 ml. 



Reducing rinse: 



potassium iodide 2.0 gm. 



sodium thiosulfate, NaoSoOg 2.0 gm. 



distilled water 40.0 ml. 



add with stirring: 



absolute ethyl alcohol 60.0 ml. 



2N HCl (page 408) 1 .0 ml. 



If a precipitate forms, allow it to settle and use solution immediately. 



Schiff 's reagent, see page 294. 



Sodium bisulfite: 



sodium metabisulfite, Na^S^Oj 0.5 gm. 



distilled water 100.0 ml. 



procedure: 



1. Deparaffinize and run slides down to 70% alcohol; remove HgCL 

 if present, using iodine in 70% alcohol. 



2. Treat with alcoholic periodic acid: 10 minutes. 



3. Rinse Avith 70% alcohol. 



4. Treat with reducing rinse: 5 minutes. 



5. Rinse in 70% alcohol. 



6. Treat with Schiff 's reagent: 10 minutes. 



7. Transfer through sulfite solutions, 3 changes: 1.5-2 minutes in 

 each (see Comment 4, page 295). 



8. Wash in running water: 5 minutes. 



9. Cotmterstain if desired (see Comments, number 3). 

 10. Dehydrate, clear, and mount. 



