Which are the two differentiation solutions used in the Weil procedure?

• A. Ammonium ferric sulfate, Borax ferricyanide
• B. Ammonium ferric sulfate, Potassium ferricyanide
• C. Borax ferricyanide, Potassium ferricyanide
• D. Ammonium ferric sulfate, Sodium borate

Answer: (A)

Two differentiation steps are used to create a distinct, contrast-rich result in the Weil procedure. The first step uses ammonium ferric sulfate as a mordant or oxidizing partner that helps set the stain so it binds more uniformly to tissue components. The second step uses borax ferricyanide as the differentiating agent, which, through its redox chemistry in a borax (sodium borate) environment, selectively removes or dulls stain from elements with lower affinity while leaving the strongly bound stain intact. This pairing provides the controlled decolorization needed to produce clear differential staining.

Using a different ferricyanide source (like potassium ferricyanide) or a different borate reagent (like sodium borate alone) would not produce the same differential effect observed with borax ferricyanide, so they aren’t used as the differentiation pair in this procedure.