Carbol fuchsin

Carbol Fuchsin is a complex organic compound used primarily as a staining agent in microbiology. It is a mixture of phenol and basic fuchsin, which is a magenta dye. This compound is particularly important in the field of bacteriology for its role in the Ziehl-Neelsen stain, a technique used to identify acid-fast bacteria, such as Mycobacterium tuberculosis.

Composition and Properties

Carbol Fuchsin is composed of basic fuchsin, which is a mixture of rosaniline, pararosaniline, and magenta II, dissolved in phenol. The phenol acts as a mordant, enhancing the dye's ability to penetrate the waxy cell walls of acid-fast bacteria. The chemical structure of rosaniline hydrochloride, a component of basic fuchsin, is depicted in the image to the right.

The dye is known for its vibrant magenta color and its ability to bind strongly to cellular components, making it an effective stain for microscopic examination.

Applications in Microbiology

Carbol Fuchsin is most famously used in the Ziehl-Neelsen stain, a differential staining technique that distinguishes acid-fast organisms from non-acid-fast organisms. In this procedure, the specimen is first stained with Carbol Fuchsin, then decolorized with an acid-alcohol solution, and finally counterstained with methylene blue or malachite green.

The acid-fast bacteria retain the Carbol Fuchsin stain due to the high lipid content in their cell walls, which resists decolorization. This property is crucial for the identification of Mycobacterium species, including the causative agents of tuberculosis and leprosy.

Preparation and Handling

Carbol Fuchsin is prepared by dissolving basic fuchsin in a solution of phenol and water. The preparation must be handled with care, as phenol is a toxic compound. Proper laboratory safety protocols, including the use of gloves and eye protection, should be followed when preparing and using Carbol Fuchsin.

Related Pages

• Ziehl-Neelsen stain
• Acid-fast bacteria
• Mycobacterium tuberculosis
• Phenol
• Basic fuchsin