A stain is a chemically defined substance, which is used to color the biological specimens, whereas dyes are crude preparations. Stains are specific dyes used to make the structural details of cells and tissue more precisely constituents visible and distinct from one another. 

i) Stains are classified into three types based on chemical nature: 

 Basic Stains, Acid Stains, Neutral Stains

Basics Stain: 

  • When stain consists of a colored organic base combined with an uncolored acetate, chloride, or sulphate radical.
  •  Example of Basic Stain: Crystal Violet,  Methylene Blue, Safranin

Acid Stain:

  • When they consist of a metallic base like sodium, potassium combined with a colored organic, radical.
  • Example of Acidic Stain: Eosin, Nigrosin, India Ink, Carbol fuschin, Malachite green

Neutral Stain: 

  • These are compounds of acid and basic dye.
  • Example of Neutral Stains: Geimsa's stain, Leishman stain, Wright's stain

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