Place a 2-mL sample of the soaking solution in a test tube. Examine the hardness of the bones. Repeat tests after 2 days in vinegar, and again after a week. The calcium ion is free to react with the oxalate ion to form a white precipitate of calcium oxalate. This is one test for the presence of calcium ion.
Calcium oxalate is insoluble in water and acetic acid.
Calcium can be removed from bone and reacted with the oxalate ion in the same manner as the known calcium source. The bones soaked in vinegar will become rubbery. The bones soaked in water will remain bone brittle. Leg bones may take a week or more. Add fresh vinegar as needed to keep bones covered and use covers on the beakers to help prevent evaporation.