Fixing Solutions and Their Uses 21 



SANFELicE FIXATIVE {Bilker, 1958): 4-6 hours. 



chromic acid, 1% aqueous (1 gm./lOO ml. water) 80.0 ml. 



formalin 40.0 ml. 



glacial acetic acid 5.0 ml. 



Mix immediately before use. Good for chromosomes and mitotic 

 spindles. Fix small pieces. Produces less final shrinkage than others 

 of this type. Wash in running water. 6-12 hours. 



schaudinn's fixative [Kessel, 1925): 10-20 minutes for smears, 40°C. 



mercuric chloride, saturated aqueous 66.0 ml. 



95% ethyl alcohol 33.0 ml. 



glacial acetic acid 5.0-10.0 ml. 



Recommended for protozoan fixation, smears on slides, or in bulk. 

 Not for tissue; produces excessive shrinkage. Transfer directly to 

 50% or 70% alcohol. Post-treat for mercuric chloride. 



sinha's fixative: 4-6 days. 



picric acid, saturated in 90% alcohol 75.0 ml. 



formalin 25.0 ml. 



nitric acid, concentrated 8.0 ml. 



Sinha {1953) adds that 5% mercuric chloride may be included; possi- 

 bly this means 5 grams per 100.0 ml. of above solution. Recom- 

 mended for insects; softens hard parts, but with no damage to internal 

 structure. Transfer directly to 95% alcohol. 



smith's fixative {Galigher, 193-i): 24 hours. 



potassium dichromate 5.0 gm. 



formalin 10.0 ml. 



distilled water 87.5 ml. 



glacial acetic acid 2.5 ml. 



Mix immediately before use. Good for yolk-rich material {Laufer, 

 1949). Wash in rinining water overnight. 



The pW of some fixatives changes after mixing and again after tissue 

 is added. This may be a factor w^orth considering luider certain condi- 

 tions — when effect on stainability or siUer impregnation is important, 

 for instance {Freeman et uL, 1955). 



