Ammonium nitrate: Characteristics
The 32 C crystal change that breaks prills
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.Commercial value depends on nitrogen content, physical form and safety. Fertiliser grades need dense, hard, non-caking granules; technical grades need porosity to absorb fuel oil. AN is hygroscopic and changes crystal phase at 32 C, which breaks prills, so stabilisers and coatings matter. Purity limits on organic matter and chlorides reduce explosion risk.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Nitrogen content | 33.5-34.5% N for AN; 27% N for CAN | price per unit N | nitrogen tile; standard grades |
| Oil absorption (technical AN) | at least about 6-8% fuel oil uptake (indicative) | ANFO performance | industry practice (indicative) |
| Bulk density | porous prills about 0.7-0.8 t/m3; dense granules about 0.9-1.0 t/m3 (indicative) | explosive energy per hole and storage | indicative |
| Combustible content | at most 0.2% for UN1942 classification | sets transport class | UN Model Regulations |
| Critical relative humidity | about 59% at 30 C (indicative) | absorbs water and cakes in humid climates | physical data (indicative) |
Commercial grades
- Technical porous prilled AN (explosives)
- High-density AN fertiliser (33.5-34.5% N)
- CAN 27% N
- AN solution for UAN and emulsions
- Medical-grade AN for nitrous oxide