Powdery monoammonium phosphate at 55 % total nutrient is an industrial intermediate, not a finished field product. It is the phosphate feedstock that NPK compound fertilizer plants meter into a granulator alongside nitrogen and potassium carriers, and it is also used as a raw material where the buyer performs their own further processing. Because it is supplied as a powder from the wet-process route, it carries the impurity load of the source phosphate rock, and the distinction between “powdery” and “water-soluble” is the single most important thing a purchaser needs to understand about it.
Substance identity
| Field | Value |
|---|---|
| Active compound | Monoammonium phosphate, NH₄H₂PO₄ |
| CAS | 7722-76-1 |
| PubChem CID | 24402 |
| Molar mass | 115.03 g/mol |
| Grade basis | 55 % = N + P₂O₅ combined |
Specification
Typical commercial range — confirm on certificate of analysis:
| Parameter | Typical |
|---|---|
| Total nutrient (N + P₂O₅) | ≥ 55 % |
| Nitrogen (N), ammoniacal | ≈ 10 – 11 % |
| P₂O₅, total | ≈ 44 – 45 % |
| Moisture | ≤ 2.0 – 3.0 % |
| Physical form | free-flowing powder |
| Appearance | grey to brown; color reflects rock source, not grade |
| Water-insoluble matter | present; declare on CoA — this grade is not a purified soluble product |
Properties
Chemically identical to any other monoammonium phosphate — the same 115.03 g/mol salt, the same mildly acidic solution reaction — but delivered at a particle size and purity intended for reprocessing.
- Reactivity in granulation. Fine particle size gives a high specific surface area, which is what makes powder MAP suitable as a granulation feed: it wets, reacts and agglomerates quickly with the binder phase.
- Impurity load. Wet-process material contains iron, aluminium, magnesium and fluoride compounds carried from the phosphate rock and acid. These raise water-insoluble content and are the reason this grade should not be used in solution.
- Dust. Powder handling generates airborne particulate; this drives the entire handling regime for the product.
- Caking tendency. Fine material with residual moisture consolidates under load in storage more readily than granular product.
Applications
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NPK compound fertilizer manufacture — the phosphate leg in rotary drum, pan or steam granulation, and in the ammoniation-granulation route.
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Dry powder blending for markets where finished product is applied in powder form.
- Feedstock for further processing into granular or specialty products by the buyer.
- Not appropriate for: drip irrigation, sprinkler injection, foliar spray, hydroponics, or any application where undissolved solids will foul emitters or leave residue on foliage. Those uses require purified technical-grade MAP ([CAS?]).
Handling and storage
Store in sealed bags or lined bulk containers in a dry, covered area; powder takes up atmospheric moisture faster than granular product of the same chemistry because of its far greater surface area. Use dust extraction at transfer and discharge points. Personnel handling open powder should use eye protection and respiratory protection appropriate to the local occupational exposure framework. Rotate stock; avoid long storage under compressive load, which causes set. Keep away from alkaline materials and from heat sources — thermal decomposition releases ammonia.
Notes
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55 % is total N + P₂O₅. It is not a P₂O₅ figure and it is not a purity figure.
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Powdery ≠ water-soluble. The two terms are routinely conflated in fertilizer trading and they describe different things: one is particle size, the other is purity.
- Where a buyer’s specification calls for “100 % water-soluble MAP”, the correct product is purified technical grade, not any of the 55/58/60 wet-process powder tiers.