A pinch of NH4Cl is added to original solution. On adding excess of NH4OH to make the solution alkaline then add freshly prepared (NH4)2CO3 solution, a white precipitate is obtained.
Ca2+ + CO32- → CaCO3
White precipitate is soluble in acetic acid.
CaCO3 + 2CH3COOH → Ca(CH3COO)2 + H2O
A white precipitate of calcium oxalate is formed on adding ammonium oxalate to above solution.
Ca(CH3COO)2 + (NH4)2C2O4 → CaC2O4