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• description

  Ammonium dihydrogen phosphate (ADP) is a transparent, piezoelectric crystal containing no water of crystallization. Single crystals of this material were originally developed for use in underwater sound projectors and hydrophones.
  
  Transducer problems during World War II fostered a joint study program on this material by Bell Telephone Laboratories, Brush Development Company and the Naval Research Laboratories. An adequate and relatively simple technology was developed in this joint effect to grow ADP crystals and to fabricate them into sonar transducers. ADP is comparable to ordinary table salt in workability, brittleness and solubility. Blumenthal was one of the first investigators to demonstrate the successful microwave modulation of light by using the electrooptic effect in ADP. ;

• Chemical properties

  Ammonium dihydrogen phosphate is a colorless transparent tetragonal crystal. soluble in water, slightly soluble in alcohol, insoluble in acetone.
  Ammonium dihydrogen phosphate or monoammonium phosphate is formed when a solution of phosphoric acid is added to ammonia until the solution is distinctly acid. It crystallizes in quadratic prisms. Monoammonium phosphate is often used in the blending of dry agricultural fertilizers. 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 powder fire extinguishers. ;

• Uses

  1. Monoammonium phosphate (MAP) is a widely used source of P and N. It is made of two constituents common in the fertilizer industry and has the highest P content of any common solid fertilizer.
  2. MAP has been an important granular fertilizer for many years. It is water soluble and dissolves rapidly in soil if adequate moisture is present. Upon dissolution, the two basic components of the fertilizer separate again to release NH4 + and H2PO4 - . Both of these nutrients are important to sustain healthy plant growth. The pH of the solution surrounding the granule is moderately acidic, making MAP an especially desirable fertilizer in neutral and high pH soils. Agronomic studies show that there is no significant difference in P nutrition from various commercial P fertilizers under most conditions.
  3. Leavening agent, dough regulator, yeast food, brewing fermentation additives and buffer in the food industry.
  4. Animal feed additives.
  5. Nitrogen and phosphorus compound fertilizer with highly efficient.
  6. Fire retardant for wood, paper, fabric, dispersant for fiber processing and dyeing industry, glaze for enamel, cooperating agent for fire retardant coating, decontamination agent for match stalk and candle core.
  7. In indurstis of printing plate and pharmaceutical manufacturing.
  ;

• Content analysis

  Accurately weighed about 500mg sample, dissolved in 50ml of water, with 0.1mol/L sodium hydroxide titration to pH 8.0. per mL, 0.1mol/L sodium hydroxide is equivalent to diammonium phosphate [NH4H2PO4] 11.50 mg.;

• Toxicity

  ADI: 0 to 70 mg/kg (amount of total phosphate as phosphorus; FAO/WHO, 2001).
  GRAS (FDA, § 184.1141a, 2000).;

• Preparation method

  Venturi loop reaction method: 85% thermal phosphoric acid will be diluted 1.3 to 1.4 times, after the measurement into the venturi tube flow mixing reactor, where it is sufficiently homogeneously mixed and reacted with the incoming ammonia gas, and the reaction process is continued in the pipeline. Finally the qualified liquid enters into the cycle reaction tank, adjusting the Ph value between the range 4.4 to 4.6, filtering and cooling the filtrate down to 26 oC, obtaining the crystal solid, separating and dehydrating, and then drying it to obtain the dihydrogen phosphate Ammonium products.
  H3PO4 + NH3 → NH4H2PO4
  Neutralization method: firstly dilute the phosphoric acid to get a solution with 50% to 55% concentration, and then take some measured solution into an enamel reaction tank with stirring and jacket. In stirring, the ammonia gas is slowly added into the ammonia tube distributor for neutralization. Waiting till the Ph value of the neutralized solution gets between 4.2~4.6, filter it immediately and send it into the cooling crystallization mold, then obtain crystallization when the temperature gets down to 26 °. Dry after dehydration and then obtain ammonium dihydrogen phosphate products.
   H3PO4 + NH3 → NH4H2PO4
  Mother liquor from separator is added into the iron remover with ammonium sulfide for removing iron, filtering, and then senting to the acid tank to adjust the acidity to Ph4.4~4.6. Refined mother liquor is supplied for recycling.
  Metathesis method Calcium dihydrogen phosphate and ammonium sulfate were melted at 85-90 °C to produce a clear solution below the saturation concentration. Firstly, the calcium dihydrogen phosphate solution is added into the reactor, and the temperature of the steam is raised to 95 oC under stirring, and the ammonium sulphate solution is added slowly for metathesis reaction to produce ammonium dihydrogen phosphate and calcium sulphate. The end point of the reaction is that Ph value is about 4.4 to 4.6. After filtration, the filtrate is sent into the evaporator to the boiling point of 108 °C, and then is sended into the cooling crystallizer, cooling to 40 °C for crystallization, centrifugal separating, drying, and then obtaining ammonium dihydrogen phosphate product.
  Ca (H2PO4) 2 H2O + (NH4) 2SO4 → This product + CaSO4 + H2O
  The separated calcium sulfate is filtered and washed to produce a by-product. The lotion is returned for the feed.;

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