Na3PO4：Na3PO4 can be recognized by its white powdery appearance and its taste of salty.

NaPO3：NaPO3 can be recognized by its white powdery appearance, taste of salty, and the presence of three hydrogen atoms.

Na4P2O7：Na4P2O7 can be recognized by its white powdery appearance, taste of salty, and the presence of four sodium atoms and two oxygen atoms.