Tissue Preparation · Histology

Why is 'Neutral Buffered' Formalin preferred over simple formaldehyde solutions?

  1. It is much less toxic to breathe
  2. It automatically stains the tissue nuclei purple
  3. It is much cheaper to produce
  4. It prevents acid hematin pigment formation
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Correct answer: It prevents acid hematin pigment formation

If formalin becomes acidic, it reacts with hemoglobin to form dark brown crystals known as acid hematin or formalin pigment. Buffering the solution to a pH of approximately 7.0 prevents this common histological artifact.

Difficulty: Medium Question 14 of 20

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