A less invasive method for determining the end of decalcification is to test the decalcifying solution rather than the tissue itself. This method is most often used with a formic acid decalcifier. Calcium is still being released if the testing solution turns cloudy and decalcification is incomplete.
Chemical method:
- Combine 5 mL of used decal solution + 5 mL ammonium hydroxide + 5 mL ammonium oxalate
- Mix and wait 30 minutes
- Calcium oxalate forms, creating a cloudy precipitate if it has calcium to bind with
- If the solution is cloudy, tissue is still releasing calcium into decal solution
- Decal solution should be changed, and tissue should continue to decalcify
- If the solution is clear, decalcification is complete
- This method is more accurate and less damaging than physical methods
- DRAWBACK: Each piece of tissue must be decalcified separately to determine the individual end-point
