All soluble orthophosphates give with silver nitrate a characteristic yellow precipitate of silver phosphate, Ag 3 PO 4, soluble in ammonia and in nitric acid.
Microcosmic salt: MH 2 PO 4 = MP0 3 +H 2 0, (NH 4) NaHPO 4 = NaP03+NH3+H20; they may also be obtained by acting with phosphorus pentoxide on trimetallic orthophosphates: Na3P04+P205 = 3NaP0 3.
On boiling their solutions they yield orthophosphates, whilst those of the heavy metals on boiling with water give a trimetallic orthophosphate and orthophosphoric acid: 3AgP0 3 +3H 2 O=Ag 3 PO 4 +2H 3 PO 4.
Of the calcium orthophosphates, the normal salt, Ca3(P04)2, is the most important.
Of the acid orthophosphates, the mono-calcium salt, CaH4(P04)2, may be obtained as crystalline scales, containing one molecule of water, by evaporating a solution of the normal salt in hydrochloric or nitric acid.