Mordant

Definition

A mordant is a chemical substance used in staining procedures to fix dyes in biological specimens. It helps to intensify the color and increase the affinity between the dye and the specimen.

5 Must Know Facts For Your Next Test

1. Mordants are essential in gram staining, where they help crystal violet bind more effectively to bacterial cell walls.
2. Common mordants include iodine, tannic acid, and potassium alum.
3. Without a mordant, stains might wash out during the decolorization step of staining procedures.
4. Mordants can also alter the color of dyes by forming complexes with them.
5. They play a crucial role in differentiating between gram-positive and gram-negative bacteria.

Review Questions

• What is the primary function of a mordant in staining procedures?
• Name two common substances that act as mordants.
• How does a mordant affect the outcome of gram staining?

Related terms

Staining:

A technique used to enhance contrast in microscopic specimens by applying dyes.

Gram Stain:

A differential staining technique that classifies bacteria into gram-positive or gram-negative based on cell wall composition.

Decolorization:

The step in a staining procedure where excess stain is removed, often using alcohol or acetone.