Ammonium dihydrogen phosphate or ADP in short is a member of ammonium phosphate family and another popular name for the chemical compound is mono ammonium phosphate or MAP. The chemical formula for the compound is little complex and written as NH4H2PO4 with a molecular mass of 115.02 g/mol. If you would look at the chemical structure of the compound then you can see that it is composed of ammonium ion and the phosphate ions.
Ammonium is a common cation that can be usually found in salts. For the phosphate anion, phosphorus is arranged in the middle and it is attached with two oxygen atoms and two hydroxyl groups around. They are connected through single bonds and double bonds.
The chemical compound is prepared by mixing ammonia and phosphoric acid together when mixed with aqueous solution and ammonia gas is passed through the mixture that is further followed by cooling to precipitate the ADP crystals.
The compound is a white crystalline solid having a density of 1.80 g/mL and melting point of 190 °C. This is quickly soluble in water absorbing moisture from the air and turns into needed product i.e. NH4H2PO4. If you would look at the chemical properties then this compound is highly stable in the air and readily decomposes to ammonia or phosphoric acid on heating. The final product has fire retardant properties too and results in explosion in the presence of sodium bicarbonate. It can be used as a dry chemical fire extinguisher too and found in science kits.