Diammonium phosphate

Diammonium phosphate (CAS 7783-28-0), commonly known as DAP, is an inorganic ammonium salt with dual function as a flame retardant and pH buffering agent. Also called secondary ammonium phosphate.

Where is Diammonium phosphate used?

• Agriculture: concentrated phosphorus-nitrogen fertilizer applied to soil or blended into NPK compound fertilizers
• Textile and leather: flame-retarding treatment for fabrics, paper and hides
• Construction: fireproofing formulations for wood, insulation boards and coatings
• Fermentation: nutrient and pH buffer in yeast-based processes such as bioethanol production and food manufacturing
• Under heat it releases ammonia and phosphoric acid, making it effective in fire suppression.
• Used as a flux for soldering tin, copper, zinc, and brass.
• Main component of ABC fire extinguishers, effective against class A, B and C fires.
• In feed it is used as a phosphorus source in mineral-supplemented compound feed production.

Formulation notes

• Incompatible with alkaline chemicals because its ammonium ion converts to ammonia in a high-pH environment.
• For basal application, provides full phosphorus and one-third to one-half of the nitrogen dose.
• Fertilizer is more effective than triple superphosphate (TSP) especially in calcareous soils with pH above 7.5.
• Should be placed below the seed and slightly to the side.

Typical specification

• Typical fertilizer grade is 18-46-0 (18% N, 46% P2O5, 0% K2O).
• Solubility is reported as approximately 588 g/L at 20 °C.
• pH is 7.6–8.2 (100 g/L in water at 20 °C).
• Offered in technical, FCC and food grades.

Regulatory status

• Has the food additive code E342(ii) and is classified as an antioxidant.

Storage, packaging and handling

• Has a lower critical relative humidity (below 70%) and is more hygroscopic than monoammonium phosphate (MAP).
• Commonly packed in 50 kg bags.
• Decomposition begins at temperatures as low as 70°C, releasing ammonia and forming monoammonium phosphate.

Frequently asked questions about Diammonium phosphate

What are the application precautions for diammonium phosphate in soil?

Placing it too close to seeds can cause seedling damage due to ammonium release and localized pH rise.

What is the optimal dosage of diammonium phosphate as a yeast nutrient?

The optimal level as a nutrient for yeast is 10-20 ppm.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.