[Jessica]

Jessica asked the Naked Scientists:
   
Will a solution containing the Mg cation form a precipitate when ammonium carbon solution is added ?

What do you think?

[Bored chemist]

I think the ammonium ions might not be the interesting bit.

[lightarrow]

It precipitates if you add ammonium *phosphate* in alcaline solution: magnesium ammonium phosphate MgNH₄PO₄ is insoluble: Ksp =2.5 x 10^-13.