Hello!
There are two tests one could use to identify a solution of Ag₃PO₄ (keep in mind that this compound is very insoluble and very little amounts of it are in solution)
For Ag⁺ ion: Precipitate with NaCl. The adding of NaCl should produce a white precipitate.
Ag⁺(aq) + NaCl(s) → AgCl(s)↓ + Na⁺
For PO₄⁻³ ion: Precipitate with Ammonium Molybdate and Acid. This reaction should produce a yellow precipitate:
PO₄⁻³ + 3NH₄⁺ + 12MoO₄⁻² + 24H⁺ → (NH₄)₃PO₄.12MoO₃(s)↓ + 12H₂O
Have a nice day!
