Bone Fix B-5

B‑5 fixative, also known as Bone Fix B‑5, is a traditional histological fixative frequently used for bone marrow biopsies, spleen, and lymphoid tissues (especially when lymphoma is suspected). It contains mercuric chloride and sodium acetate in water, and is mixed with formaldehyde immediately before use to form the working solution.

🏭⚗️ Production
Prepared in two stages: first, a stock solution is made by dissolving mercuric chloride (~12 g) and sodium acetate (~2.5 g) in 200 mL of distilled water. Immediately before use, a working solution is prepared by mixing approximately 20 mL of the stock with 2 mL of 40% formaldehyde.

🔬 Properties
B‑5 fixative delivers exceptional nuclear and cytoplasmic detail, making it a gold standard for hematopoietic tissue fixation. However, it contains toxic mercury and formaldehyde, presents disposal challenges, can corrode metals, and may result in tissue hardening. Additionally, fixation schedules are strict—over-fixation can occur if not monitored. Mercury pigment formed during fixation must be removed (e.g., via iodine treatment followed by thiosulfate wash) before staining.

🧪 Applications
• Histopathology: Preferred for bone marrow biopsies, spleen, and lymph nodes when detailed morphology is required or lymphoma is suspected.
• Special staining & immunohistochemistry: Produces sharp nuclear morphology and is compatible with various staining techniques, though care must be taken to remove mercury pigments beforehand.
• Diagnostic precision: Especially useful when fine chromatin patterns and nuclear detail are critical for interpretation.