This is one way sodium metal can be isolated using NaOH and Mg. Mg has a strong enough desire for oxygen to tear it from the NaOH, leaving ingots of elemental sodium behind. 2Mg + 2NaOH = 2MgO + 2Na + ...

Result Brown precipitate which remains when excess NaOH solution or excess NH 3 solution added. Cation Mg 2+ Test Make into a solution and add an excess of NaOH solution or NH 3 solution.