Ammonium chloride supplies nitrogen entirely in the ammonium form, and this determines how it behaves from the moment it dissolves. Ammonium is a cation and is held on soil exchange sites; nitrate is an anion and is not. That single distinction governs leaching, loss pathway, acidification and the appropriate timing and placement of the fertilizer. This page is the chemistry hub for the family; form- and grade-specific pages sit beneath it.
Substance identity
| Chemical name | Ammonium chloride |
| Synonyms | Sal ammoniac, salmiac, muriate of ammonia, ammonium muriate |
| Formula | NH₄Cl |
| CAS | 12125-02-9 |
| PubChem CID | 25517 |
| EC number | 235-186-4 — verify against the current ECHA entry before publication |
| Molar mass | 53.49 g/mol |
| Appearance | White to off-white crystalline solid or granules |
Specification
| Parameter | Value | Basis |
|---|---|---|
| Nitrogen (N), theoretical | 26.2 % | Calculated: 14.007 / 53.49 |
| Chloride (Cl), theoretical | 66.3 % | Calculated: 35.453 / 53.49 |
| Nitrogen form | 100 % ammonium (NH₄⁺-N); no nitrate, no amide | Structural |
| Nitrogen, agricultural grade | ≥ 25.0–25.4 % | Typical commercial range |
| Sulfur | None | The compound contains no sulfur |
Properties
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Solubility. Approximately 29 g per 100 g water at 0 °C, 37 g at 20 °C, 77 g at 100 °C. Fully dissolved in soil moisture within a normal irrigation or rainfall event.
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Dissolution enthalpy. Endothermic, about +14.8 kJ/mol.
- Solution pH. 4.5–6.0 for a 5 % solution at 25 °C, because NH₄⁺ (pKa 9.25) hydrolyses in water. Note that this initial acidity is minor compared with the acidity generated later by nitrification.
- Hygroscopicity. Critical relative humidity around 77 % at 30 °C.
- Thermal behaviour. Dissociates to NH₃ and HCl on heating; apparent sublimation near 337.6 °C.
Applications
Three properties determine where this product fits.
Ammonium is retained, then converted. Dissolved NH₄⁺ adsorbs to clay and organic matter exchange sites and resists leaching. Soil bacteria then oxidise it to nitrate — nitrification — and once that conversion occurs the nitrogen is mobile and leachable like any other nitrate. The practical consequence is a delay, not immunity: ammonium fertilizer applied to a soil with active nitrification is nitrate fertilizer within weeks, and faster in warm, moist, well-aerated soil.
Nitrification acidifies. The reaction NH₄⁺ + 2 O₂ → NO₃⁻ + 2 H⁺ + H₂O releases two protons per nitrogen. This is intrinsic to all ammonium sources. Because ammonium chloride carries more nitrogen per tonne than ammonium sulfate, its acidification per tonne of product is greater, which is a factor to plan for on acid or weakly buffered soils and can be an advantage on calcareous ones.
The counter-ion is chloride. Chloride is an essential plant micronutrient, so it is not inert ballast. It also avoids introducing sulfate, which matters in waterlogged soils where sulfate can be microbially reduced to sulfide. Chloride has additionally been reported in the agronomic literature to slow nitrification relative to sulfate-based ammonium sources, and to reduce the severity of certain cereal root diseases; both effects are reported rather than guaranteed, and are conditional on soil and season.
Handling and storage
Store dry, sealed and away from alkaline materials, which liberate ammonia on contact and destroy the nitrogen value. Avoid direct seed contact — the salt contributes meaningfully to soil solution salinity, and germinating seed is the most salt-sensitive stage of the crop. Corrosive to copper alloys and unprotected steel in humid conditions.
Notes
The suitability of this fertilizer is decided by the crop’s chloride tolerance, not by its nitrogen requirement. Where chloride is unwelcome, the nitrogen is unwelcome with it, and no application technique changes that. Crop-by-crop guidance is on the agriculture-grade page.
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Frequently asked questions
What is the difference between fertilizer-grade and technical-grade ammonium chloride, and does the production route matter?
There are two common routes. Most fertilizer-grade material is a co-product of soda ash manufacture (the ammonia-soda or combined-alkali process), where the limiting impurity is residual sodium chloride and the crystal is usually fine and white. Technical, battery, food and pharmaceutical grades are more often produced by neutralizing hydrochloric acid with ammonia and are purified further, with tighter limits on sulfate, iron, heavy metals and water-insoluble matter. For fertilizer use the practical differences are nitrogen content, sodium chloride carry-over, moisture and particle size, not the route itself. Ask for the actual certificate of analysis rather than relying on the grade name, since grade names are not standardized between suppliers.
Nitrogen is quoted as a minimum percentage. How should I actually compare two offers?
Convert everything to cost per unit of nitrogen delivered, not cost per tonne of product. Pure NH4Cl contains about 26.2% N; commercial fertilizer grades are typically guaranteed somewhat below that because of sodium chloride and moisture. A cheaper tonne with a lower nitrogen guarantee and higher moisture can cost more per kilogram of N than a dearer one. Check three things on the specification: whether nitrogen is guaranteed on a dry basis or as received, the moisture ceiling, and the sodium chloride or water-soluble impurity limit, because NaCl adds salinity without adding nutrient.
Does ammonium chloride acidify soil, and what should I plan for?
Yes. The nitrogen is supplied entirely in ammonium form, and when soil microbes nitrify it to nitrate they release hydrogen ions, so the residual effect on the soil is acidifying. Per unit of nitrogen it sits in the same band as ammonium sulfate and well above urea or calcium nitrate. On buffered, calcareous or naturally alkaline soils this is often an advantage and can improve availability of iron, manganese and zinc. On soils already at low pH, or with weak buffering such as sandy soils, repeated use without a liming program will drive pH down and can mobilize aluminium and manganese. Base the lime requirement on local soil tests and lime quality, not on a generic factor.
When is ammonium chloride the wrong choice?
Avoid it wherever chloride, not nitrogen, is the constraint. Roughly two-thirds of the mass is chloride, so chloride-sensitive crops — tobacco, potatoes grown for starch content or crisping quality, grapevines, many stone fruits and citrus, strawberries, beans, onions and several ornamentals — can show quality or yield penalties. Avoid it on saline or sodic soils, and in dry climates or under drip irrigation where there is no leaching fraction to move chloride below the root zone. It is a poor fit for closed hydroponic systems and for EC-limited fertigation. It is also the wrong product when the crop needs nitrate nitrogen early in a cold season, because nitrification is slow at low soil temperature.
Why does it cake in the warehouse, and how should it be stored?
It is hygroscopic. Above roughly the mid-seventies in percent relative humidity — the exact critical humidity depends on temperature and on impurities — the crystals take up water, and when the air dries again the dissolved salt recrystallizes into bridges between particles, so the bag sets solid. Humidity cycling, not average humidity, does most of the damage. Store sealed in moisture-barrier bags or lined bulk bags, on pallets, away from walls and off bare concrete, in a shaded and ventilated building, and rotate stock. Limit stack height and storage time, because pressure caking compounds moisture caking. Keep it away from bare mild steel and galvanized surfaces: damp ammonium chloride is corrosive to both.
What should it never be blended with or stored beside?
Never blend it with alkaline materials — lime, dolomite, basic slag, calcium cyanamide or fresh wood ash. They liberate free ammonia, so nitrogen is lost, the pile smells, and the blend can turn wet and warm. Keep it away from hypochlorites and other strong oxidizers, and from nitrites, which give hazardous reactions with ammonium salts. In bulk blends, evaluate the critical relative humidity of the mixture rather than of each component alone: pairing ammonium chloride with urea or with ammonium nitrate lowers the point at which the blend begins absorbing moisture, so it cakes faster than either component would separately. Do not expose it to open flame or hot surfaces; strong heating dissociates it into ammonia and hydrogen chloride as a corrosive white fume.
Should I buy the crystalline powder or the granular grade?
It depends on what happens downstream. Fine crystalline material is normally bought as a raw material for compound NPK manufacture, where it is dissolved, slurried or compacted with other components, and for non-fertilizer industrial use. Granular or compacted grades are intended for direct field application and for bulk blending with granular urea, MAP, DAP or potash. For blending, the size distribution matters more than the average size: if the ammonium chloride granules are noticeably finer or coarser than the partner products, the blend segregates during handling and the field receives uneven nitrogen. Granules also dust less, flow better through spreaders and resist caking better than crystal, and normally carry a modest premium per unit of nitrogen.
Related substances
- If the soil also needs sulphur, or the crop is chloride-sensitive, ammonium sulphate supplies the same ammoniacal nitrogen with sulphate rather than chloride as the companion ion.
- Urea carries roughly 46% N against roughly 26% for ammonium chloride but must be hydrolysed by urease before the plant sees ammonium, which is why its surface-application losses behave along a different pathway from those of ammonium chloride.
- Ammonium chloride is the nitrogen-bearing co-product of the ammonia-soda route to soda ash, so the soda ash page explains where this fertilizer physically comes from.