A good substitute for one chemical in the primary staining solution used to color the purple fibers is which chemical?

• A. Acetaldehyde
• B. Formaldehyde
• C. Glyceraldehyde
• D. Sodium nitrite

Answer: (A)

The staining result relies on a fixative that helps the dye bond to tissue components, enabling the target fibers to take up color properly. In many primary staining solutions, an aldehyde fixative is used to cross-link proteins and stabilize structure so the dye interacts consistently, producing the characteristic purple appearance of those fibers. Acetaldehyde can perform this same function because it behaves like formaldehyde in forming cross-links with tissue proteins. Because of that similar chemistry, acetaldehyde can substitute for formaldehyde in the primary staining solution and yield comparable staining of the purple fibers. The other options don’t provide the same cross-linking effect needed for that color development.