Diammonium phosphate (DAP;

IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

name diammonium hydrogen phosphate; chemical formula (NH₄)₂(HPO₄)) is one of a series of

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

- soluble ammonium phosphate salts that can be produced when

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

reacts with

phosphoric acid Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, ...

. Solid diammonium phosphate shows a dissociation pressure of ammonia as given by the following expression and equation: : At 100 °C, the dissociation pressure of diammonium phosphate is approximately 5 mmHg. According to the diammonium phosphate MSDS from CF Industries, Inc., decomposition starts as low as 70 °C: "Hazardous Decomposition Products: Gradually loses ammonia when exposed to air at room temperature. Decomposes to ammonia and monoammonium phosphate at around 70 °C (158 °F). At 155 °C (311 °F), DAP emits phosphorus oxides, nitrogen oxides and ammonia."

Uses

DAP is used as a fertilizer. When applied as plant fertilizer, it temporarily increases the

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

pH, but over a long term the treated ground becomes more acidic than before, upon nitrification of the ammonium. It is incompatible with

alkaline In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The ...

chemicals because its

ammonium Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged (cationic) polyatomic ion, molecular ion with the chemical formula or . It is formed by the protonation, addition of a proton (a hydrogen nucleu ...

ion is more likely to convert to

in a high-pH environment. The average pH in solution is 7.5–8. The typical formulation is 18-46-0 (18% N, 46% P₂O₅, 0% K₂O). DAP can be used as a fire retardant. It lowers the combustion temperature of the material, decreases maximum weight loss rates, and causes an increase in the production of residue or char. These are important effects in fighting

wildfires A wildfire, forest fire, or a bushfire is an unplanned and uncontrolled fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identified as a ...

as lowering the

pyrolysis Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Gree ...

temperature and increasing the amount of char formed reduces that amount of available fuel and can lead to the formation of a firebreak. DAP is also used as a yeast nutrient in winemaking and

mead Mead (), also called honey wine, and hydromel (particularly when low in alcohol content), is an alcoholic beverage made by fermenting honey mixed with water, and sometimes with added ingredients such as fruits, spices, grains, or hops. The alco ...

-making; as an additive in some brands of cigarettes purportedly as a nicotine enhancer; to prevent afterglow in matches, in purifying

sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...

; as a flux for soldering tin, copper, zinc and brass; and to control

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...

of alkali-soluble and acid-insoluble colloidal dyes on

wool Wool is the textile fiber obtained from sheep and other mammals, especially goats, rabbits, and camelids. The term may also refer to inorganic materials, such as mineral wool and glass wool, that have some properties similar to animal w ...

Natural occurrence

The compound occurs in the nature as the exceedingly rare mineral phosphammite. The related dihydrogen compound occurs as the mineral biphosphammite. Both are related to guano deposits.

References

External links

International Chemical Safety Card 0217
{{Phosphates Ammonium compounds Phosphates Inorganic fertilizers