14 - Fixation (chap. 1) 



BUFFERED FORMALIN: may remain indefinitely, progressive action. 



\0% formalin 1000.0 ml. 



sodium acid phosphate, NaH2P04H20 4.0 gm. 



anhydrous disodium phosphate, Na2HP04 ... 6.5 gm. 



Wash in water. 



FORMALIN (Baker, 1944): may remain indefinitely, progressive action. 



calcium chloride 1-0 gm. 



cadmium chloride 1.0 gm. 



formalin 10.0 ml. 



distilled water 100.0 ml. 



Wash in water. 



FORMALIN {Baker, 1958): may remain indefinitely, progressive action. 



formalin 10.0 ml. 



calcium chloride (anhydrous) 10% aqueous so- 

 lution (10 gm./lOO ml. water) 10.0 ml. 



distilled water 80.0 ml. 



Wash in water. 



helly's fixative (ZENKER formol): 6-24 hours. If the tissue seems to 

 harden excessively, follow a maximum of 18 hours in fixative with 

 a 12-24 hour chromating in 3% potassium dichromate. 



potassium dichromate 2.5 gm. 



mercuric chloride 4.0-5.0 gm. 



sodium sulfate 1.0 gm. 



(may be omitted, see indifferent salts, page 10) 



distilled water 100.0 ml. 



formalin (add just before using) 5.0 ml. 



Formalin reduces dichromate and should not be left in stock solu- 

 tions. The above stock, without formalin, can be used for Zenker's 

 fixative, page 16. Excellent for bone marrow and blood-forming 

 organs, also intercalated discs. Wash in running water overnight, 

 post-treat for mercuric chloride. Maximow modification: add 10% 

 of formalin instead of 5%, and sometimes 10% of osmic acid. The 

 latter should be fixed in the dark. 



