40 ' Paraffin Method (chap. 3) 



Miller's Schedule for Dioxane (1937) 



1. Move directly from fixative into dioxane 3 parts, distilled water 1 

 part: |-1 hour. 



2. Dioxane: 1 hour, 



3. Fresh dioxane: 2 hours. 



4. Paraffin 1 part, dioxane 1 part (in paraffin oven): 2-4 hours. 



5. Paraffin: overnight. 



6. Embed. 



Many technicians consider it advisable to place anhydrous calcium 

 chloride in the bottom of the dioxane container during dehydration as 

 an aid in removal of all water, thereby reducing the possibility of carry- 

 ing water into the paraffin. Mossman (1937) observed that dioxane reacts 

 with CaCl2 and makes it swell as though water is present. He suggested 

 that CaO (calcium oxide) is better, but feels that this step is unnecessary. 



If a fixative containing potassium dichromate is used, the tissues must 

 be washed thoroughly before using dioxane; otherwise the dichromate 

 will crystallize. 



Tetrahydrofuran (THF) for Dehydration 



Haust {1958, 1959) recommends THF for dehydration for several 

 reasons. It mixes with water in all proportions, also with paraffin de- 

 pending upon temperature, becoming increasingly miscible as the 

 temperature rises. It is miscible with nearly all solvents and can be used 

 as a solvent for mounting media. Most dyes are not soluble in THF, biu 

 iodine, mercuric chloride, acetic acid and picric acid are soluble in it. 

 THF has a low boiling point (65 °C) so it evaporates rapidly and must 

 be kept tightly closed at all times. It has to be regenerated occasionally 

 to remove accumulated peroxides and water. 



Haust's Method, Following Fixation 



1. THF 1 part, water 1 part: 2 hours. 



2. THF, 3 changes: 2 hours each. 



3. THF I part, paraffin 1 part, 53-54°C: 2 hours. 



4. Paraffin: 2 hours. 



5. Embed. 



Tetrahydrofuran, highest quality, can be obtained from Eastman 

 Kodak Co., and Fisher Sciejitific Co. 



The Fisher Company in The Laboratory, Clinical Edition (28, #C4, 

 1960), suggests that instead of repurifying THF over metallic sodium, a 



