Clearing Agents

• Xylene or Xylol


  = Most commonly used clearing agent

  
  

  = Most RAPID clearing agent (15-30 minutes)

  
  

  = NOT suitable for Nervous tissues and lymph nodes= Becomes MILKY when an INCOMPLETELY DEHYDRATED tissue is immersed in it
• Toluene


  May be used as a substitute for xylene or benzene for clearing both during embedding and mounting processes.
• Chloroform


  = For TOUGH tissues = Does not make tissue transparent

  = Toxic to liver
• Benzene


  For urgent biopsies

  Minimum shrinkage

  Aplastic anemia

  EXTREMELY TOXIC and may become CARCINOGENIC
• For double embedding techniques

  Methyl salicylate and Methyl benzoate
• Cedarwood oil


  For CNS, smooth muscles, skin

  = Becomes MILKY upon PROLONGED STORAGE and should be filtered before use

  = Used to clear both paraffin and celloidin sections during the embedding process
• Aniline Oil


  Recommended for clearing embryos, insects and very delicate specimens
• Clove


  Quality is not guaranteed due to its tendency to become adulterated
• Dioxane & Tetrahydrofuran


  Both a dehydrating and clearing agent
• Other Xylene Substitutes:


  Terpenes (Plant oils) - Earliest transition solvents used in histology

  Limonene - Xylene substitute from the terpene family, derived from oil of citrus peels
• Other clearing agents


  N-Butyl Acetate

  
  

  Terpenes

  
  

  Orange Oil

  
  

  Chlorinated hydrocarbons

  
  

  Coconut Oil

  
  

  Bleached Palm Oil
• CLEARING/ DEALCOHOLIZATION

  Removal of alcohol from tissue and replaced with a substance that will dissolve the wax where the tissue is to be impregnated
• Ideal clearing agent:

  1. Should be miscible with alcohoL
  2. Should be miscible with paraffin
  3. Should not produce excessive shrinkage, hardening or damage to the tissue
  4. High refraction index
  5. Should make tissue transparent