Granular technical grade ammonium chloride is high-purity material supplied in a coarse particle form. The choice between granular and powder at the same purity is a process-engineering decision, not a chemical one, and it turns on a genuine trade-off: granules dose cleanly and dust less, powder dissolves faster. Which side of that trade-off a plant sits on is determined by whether its bottleneck is handling or dissolution.
Substance identity
| Chemical name | Ammonium chloride |
| Synonyms | Sal ammoniac, ammonium muriate |
| Formula | NH₄Cl |
| CAS | 12125-02-9 |
| PubChem CID | 25517 |
| Molar mass | 53.49 g/mol |
| Appearance | White granules, typically angular where produced by compaction and crushing |
Specification
| Parameter | Value | Basis |
|---|---|---|
| NH₄Cl content, dry basis | ≥ 99.5 % | Typical technical grade floor |
| Moisture | ≤ 0.3–0.5 % | Typical commercial range |
| Water-insoluble matter | ≤ 0.02–0.05 % | Typical commercial range |
| Sulfate (SO₄) | ≤ 0.02–0.05 % | Typical commercial range |
| Iron (Fe) | ≤ 5–10 mg/kg | Typical commercial range |
| Particle size | 2–4 mm is a common cut; finer cuts are produced where dissolution rate matters | Typical commercial cuts |
| Bulk density | Approximately 0.9–1.05 t/m³ | Typical, approximate |
| pH, 5 % solution at 25 °C | 4.5–6.0 | Typical range |
Properties
Chemistry is that of the salt, unchanged by granulation: solubility approximately 37 g per 100 g water at 20 °C rising to about 77 g at 100 °C; endothermic dissolution at about +14.8 kJ/mol; solution pH 4.5–6.0 at 5 %; dissociation to ammonia and hydrogen chloride on heating with apparent sublimation near 337.6 °C.
Granulation governs rate. Dissolution rate is proportional to exposed surface area, and a 3 mm granule offers roughly an order of magnitude less surface per unit mass than a 0.3 mm crystal. The dissolution rate difference is correspondingly large, and it is the single number a process engineer should establish before switching form. Test it in the actual vessel, at the actual temperature and agitation, because agitation and temperature affect granules and powder differently — vigorous agitation narrows the gap, quiescent dissolution widens it.
Applications
Metered feeding. Granules flow more consistently than powder through screw feeders, rotary valves and gravimetric feeders. Powder bridges, rat-holes and flushes; granules mostly do not. Where the salt is dosed continuously into a process, feed consistency translates directly into process consistency.
Dust and exposure control. Airborne ammonium chloride is an eye and respiratory irritant, and settled dust corrodes electrical equipment and steelwork in humid plant environments. Granules reduce both problems substantially, which is often the whole reason for choosing them.
Controlled dissolution. In some processes slower, more gradual dissolution is preferred — where a rapid concentration spike would disturb a bath or where dissolution occurs during transit through a mixing loop. Here the granule is not a compromise but the correct choice.
Where powder wins. Batch make-up of concentrated solutions against a clock, and any application where the salt must dissolve completely before a downstream step. Do not choose granules for a dissolution-limited process on the strength of their handling advantages.
Handling and storage
Dry, sealed storage. Granules resist caking better than powder because of their lower surface area, but the salt’s critical relative humidity near 77 % at 30 °C is unchanged and the improvement is in rate rather than in equilibrium. Limit drop heights and transfer points — attrition generates fines, and fines reintroduce both the dust exposure and the caking initiation that granulation was chosen to avoid. Keep away from strong alkalis, strong oxidisers, silver salts, chlorates and nitrites. Protect copper alloys, mild steel, galvanised steel and aluminium from contact in humid conditions; chloride raises pitting risk on austenitic stainless steel.
Notes
Purity and form are independent variables and should be specified independently. A granular product is not purer than a powder because it looks cleaner, and a high assay says nothing about size distribution or dust content. Specify both, with methods, and verify both on arrival.