Magnesium Phosphide, Mg₃P₂

When calcium phosphate and magnesium are heated together, the action is violent and magnesium phosphide is apparently produced. It was also obtained by heating magnesium with various substances, organic or inorganic, containing phosphorus.

It has been more effectively prepared by heating magnesium in phosphorus vapour and carbon dioxide, and by the direct union of magnesium and phosphorus. Gautier heated magnesium in phosphorus vapour and hydrogen, and obtained small, brilliant, dark green-grey crystals corresponding to Mg₃P₂. Magnesium phosphide is stable in dry air, but readily decomposed by moisture into magnesium hydroxide and pure hydrogen phosphide. The halogens and ordinary mineral acids also decompose it, and it burns at a dull red heat in oxygen to magnesium phosphate.