Product Description
Diammonium hydrogen phosphate is a white crystal that is neutral in aqueous solution. Its molecular formula is (NH4)2HPO4, soluble in water, heated to 155ºC decomposition. Ammonium mono-hydrogen phosphate will gradually break down to release ammonia gas, and form ammonium dihydrogen phosphate.
Diammonium hydrogen phosphate
structure
The hydrogen phosphate ion in diammonium hydrogen phosphate molecule is composed of phospho-oxygen tetrahedron, which is connected with two ammonium ions by ionic bond.
In phosphoric acid, the P atom is sp3 hybrid, three hybrid orbitals form three σ bonds with the oxygen atom, and the other P-O bond is composed of one σ bond from phosphorus to oxygen and two d-p bonds from oxygen to phosphorus. A σ bond is formed when a lone pair of electrons from a phosphorus atom coordinates to an empty orbital of an oxygen atom. The d←p bond is formed by overlapping the py and pz lone pairs of oxygen atoms with the dxz and dyz empty orbitals of phosphorus atoms. Since the 3d energy level of the phosphorus atom is much higher than the 2p energy level of the oxygen atom, the molecular orbital is not very efficient, so the P-O bond is triple in terms of number, but in terms of bond energy and bond length, it is between single and double bonds.
Physical and chemical properties
Diammonium hydrogen phosphate is colorless transparent and odorless monoclinic crystal or white powder. The relative density is 1.619. Melting point 100ºC, decomposition during melting. It has a salty, minty flavor. Soluble in water, aqueous solution is alkaline, insoluble in alcohol and acetone.
PH: The pH of 1% aqueous solution is about 8, and the pH of 0.1mol/L solution is 7.8.
use
Diammonium hydrogen phosphate can be used as fertilizer. When used as a fertilizer for plants, it will temporarily increase the pH of the soil, but after a long period of nitrification, the soil treated with ammonium monohydrogen phosphate will become more acidic than before. Since ammonium is converted to ammonia in highly alkaline environments, mono-ammonium phosphate and base are incompatible. The average pH of ammonium monohydrogen phosphate solution is 7.5-8.
Diammonium hydrogen phosphate can also be used as a flame retardant. It reduces the combustion temperature of the material, reduces the maximum weight loss rate, and increases residues. These properties can be used to fight wildfires, as lowering the thermal cracking temperature and increasing the amount of coke formed reduces the amount of fuel available and may create fire breaks. It is the largest ingredient in some popular commercial firefighting products, as well as an ingredient in "flame retardant" cigarettes.
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