DEHYDKATIOK 



As none of the usual clearing agents, used previous to 

 mounting in Balsam, will mix with aqueous fluids, sections 

 must be dehydrated before clearing. The usual dehydrating 

 agent is Alcohol, and the only point which requires notice is 

 the strength to be employed. 



Preparatory to clearing in Oil of Cloves or Bergamot, 90 

 p. c. Alcohol answers every purpose. But for Oil of Cedar 

 or the other members of the Xylol group, Alcohol of at least 

 96 p. c. must be used, and Absolute Alcohol is preferable. 



Celloidin Sections. Oil of Bergamot clears Celloidin 

 without dissolving it, and as this oil can be used after 90 p. c. 

 Alcohol, it possesses great advantages. 



Cedar Oil also clears Celloidin, but as the film is quickly 

 acted upon by Absolute (98 p. c.) Alcohol, it is safer to use a 

 slightly hydrated Alcohol 96 p. c. (sp. gr. 0-807 at 60 F.), 

 made by adding 2 cc. of Water to 120 cc. of Absolute Alcohol. 

 This will clear into either Oil of Cedar or Xylol, and in 15 

 minutes (the maximum time required for dehydrating sections) 

 will not perceptibly attack the celloidin. These sections can 

 also be dehydrated in Absolute Alcohol, but it must be done 

 quickly (about 2 minutes) or the celloidin film will be per- 

 ceptibly affected. 



The only other dehydrating agent that may be mentioned 

 is Aniline, used in special circumstances where strong Alcohol 

 must be avoided. This clears readily from 70 p. c. Alcohol, and 

 is replaced before mounting by Cedar Oil, Benzol, or X}4ol. 



