272 Cytoplasmic Elements (chap. 18) 



Colloidal Iron Method (mowry, 1958) 



solutions: 



Colloidal iron solution: 



Stock solution: 



Bring 250 ml. distilled water to boil. While boiling pour in 4.4 ml. 

 of 29% ferric chloride (USP XI) solution. Stir. When solution is 

 dark red, remove from heat and allow to cool. The color must be dark 

 red and clear. It is stable for months. 



Working solution: 



glacial acetic acid 5.0 ml. 



distilled water 15.0 ml. 



stock colloidal iron solution 20.0 ml. 



pH should be 1.1-1.3. Nonspecific staining takes place at pH 1.4 or 

 higher. Effective for 1 day. 



Hydrochloric acid-ferrocyanide. 



2% HCl (2 ml./98 ml. water) 50.0 ml. 



2% potassium ferrocyanide (2 gm./lOO ml. 



water) 50.0 ml. 



Mix immediately before use. 



procedure: 



1. Deparaffinize and hydrate slides to water: remove HgClo. 



2. Rinse in 12% acetic acid (12 ml./88 ml. water): 30 seconds (pre- 

 vents dilution of reagent). 



3. Transfer to freshly prepared colloidal iron (working solution): 60 

 minutes. 



4. Rinse in 12% acetic acid, 4 changes: 3 minutes each. 



5. Treat with hydrochloric acid-ferrocyanide, room temperature: 20 

 minutes. (Include a control slide, one not treated with colloidal 

 iron.) 



6. Wash in running water: 5 minutes. 



7. Counterstain if desired: Feulgen, PAS, or hematoxylin. 



8. Optional: dip in aqtieotis picric acid to color cytoplasm and 

 erythrocytes; rinse for fcAv seconds in tap water. (Author's com- 

 ment: acetic-orange G also may be used.) 



9. Dehydrate, clear, and mount. 



results: 



acid mucopolysaccharides — bright blue; uncolored in control slide, 

 mucins of connective tissue, epithelium, mast cell grantdes, capstdes 

 of some microbial agents, pneumococci — bright blue 



