Which stain uses a saturated solution of picric acid in the primary stain?

• A. Van Gieson
• B. Aldehyde fuchsin
• C. Masson trichrome
• D. Oil Red O

Answer: (A)

Van Gieson uses a saturated picric acid solution as the primary stain to color collagen yellow, with acid fuchsin providing the red counterstain for other tissue elements. This combination creates a clear differentiation where connective tissue (collagen) appears yellow and muscle or cytoplasm appears red. The other stains work by different mechanisms: aldehyde fuchsin targets elastic fibers, Masson trichrome uses three dyes in a multipstep process, and Oil Red O stains lipids in frozen sections, none of which rely on a saturated picric acid primary stain.