Ammonium dihydrogen phosphate
Encyclopedia
Ammonium dihydrogen phosphate (ADP), or monoammonium phosphate, NH4H2PO4, is formed when a solution of phosphoric acid
is added to ammonia
until the solution is distinctly acid
ic. It crystallizes in tetragonal prisms
. Monoammonium phosphate is often used in the blending of dry agricultural fertilizer
s. It supplies soil
with the elements nitrogen
and phosphorus
in a form which is usable by plants. The compound is also a component of the ABC powder
in some dry chemical fire extinguisher
s. This substance is also supplied in an emerald green or aquamarine crystal growing box kit for children.
Solid monoammonium phosphate show a dissociation pressure of ammonia of 0.05 mmHg at 125°C based on the decomposition reaction as follows:
ADP is a widely used crystal in the field of optics due to its birefringence
properties. As a result of its tetragonal crystal structure, this material has negative uniaxial optical symmetry with typical refractive indices no=1.522 an ne=1.478 at optical wavelengths.
ADP crystals are piezoelectric which is a property required in some active sonar
transducers (the alternative being transducers that use magnetostriction
). In the 1950s ADP crystals largely replaced the Quartz
and Rochelle Salt crystals in transducers because they are easier to work than Quartz and, unlike Rochelle Salt, are not deliquescent.
Phosphoric acid
Phosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way...
is added to ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
until the solution is distinctly acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
ic. It crystallizes in tetragonal prisms
Prism (geometry)
In geometry, a prism is a polyhedron with an n-sided polygonal base, a translated copy , and n other faces joining corresponding sides of the two bases. All cross-sections parallel to the base faces are the same. Prisms are named for their base, so a prism with a pentagonal base is called a...
. Monoammonium phosphate is often used in the blending of dry agricultural fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
s. It supplies soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
with the elements nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
and phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
in a form which is usable by plants. The compound is also a component of the ABC powder
ABC Dry Chemical
ABC or multi-purpose dry chemical is a dry chemical extinguishing agent. It uses a specially fluidized and siliconized monoammonium phosphate powder. ABC dry chemical is usually a mix of monoammonium phosphate and ammonium sulfate, the former being the active one. The mix between the two agents is...
in some dry chemical fire extinguisher
Fire extinguisher
A fire extinguisher or extinguisher, flame entinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations...
s. This substance is also supplied in an emerald green or aquamarine crystal growing box kit for children.
Solid monoammonium phosphate show a dissociation pressure of ammonia of 0.05 mmHg at 125°C based on the decomposition reaction as follows:
- NH4H2PO4(s) NH3(g) + H3PO4(l)
ADP is a widely used crystal in the field of optics due to its birefringence
Birefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...
properties. As a result of its tetragonal crystal structure, this material has negative uniaxial optical symmetry with typical refractive indices no=1.522 an ne=1.478 at optical wavelengths.
ADP crystals are piezoelectric which is a property required in some active sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
transducers (the alternative being transducers that use magnetostriction
Magnetostriction
Magnetostriction is a property of ferromagnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of material's magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ...
). In the 1950s ADP crystals largely replaced the Quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
and Rochelle Salt crystals in transducers because they are easier to work than Quartz and, unlike Rochelle Salt, are not deliquescent.