Question

An aspirin product on the market claims to use magnesium hydroxide, Mg(OH)2, as a buffering agent. How could you verify whether magnesium ions are present?

Answer 1

1. You need add some acid (HCl) to aspirinem(if Mg(OH)₂ is present it must react with acid)
Mg(OH)₂ + 2HCl = MgCl₂ + 2H₂O
2. Than we need add Na₂HPO₄
MgCl₂ + Na₂HPO₄ = 2NaCl + MgHPO₄ (it precipitates)
precipitate should be white and crystalline

Also Mg²⁺ reacted with Titanium yellow, C₂₈H₁₉N₅Na₂O₆S₄,giving red precipitate.