Inorganic Chemicals

Formula : (NH4)2HPO4; MW 132.07;

Synonyms: diammonium hydrogen phosphate; secondary ammonium phosphate

Uses
Dibasic ammonium phosphate is used as a fertilizer; as a fire extinguisher; a flame retardant for plywood, papers, and fabrics; to prevent afterglow in matches; in purifying sugar; as a flux for soldering tin, copper, zinc and brass; and to control precipitation of alkali-soluble or acid-insoluble colloidal dyes on wool.

Physical Properties
Colorless monoclinic crystal; saline taste; refractive index 1.52; density 1.619 g/cm³; melts at 155°C (decomposes); very soluble in water (57 g/100 g at 10°C and 106.7g/100g at 70°C, respectively); insoluble in alcohol, acetone, and liquid ammonia.

Preparation
is made by reacting ammonia with phosphoric acid:

Reactions
Heating at 70°C results in decomposition to monoammonium phosphate and ammonia:

A boiling, dilute solution of diammonium phosphate evolves ammonia (the pH of the solution decreases), which also occurs slowly at ambient temperatures. The solid and its solution create an ammonia vapor pressure. Reactions with mineral acids produce the corresponding ammonium salts.