Sal-ammoniac
Chemical Formula	NH4Cl
Species	Halides

Ammonium chloride, an inorganic compound with the formula NH₄Cl, is a white crystalline salt, highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of the natural, mineralogical form of ammonium chloride. The mineral is commonly formed on burning coal dumps, due to condensation of coal-derived gases. It is also found around some types of volcanic vent. It is used as a flavouring agent in some types of liquorice. It is the product from the reaction of hydrochloric acid and ammonia.

Sources

It is a product of the Solvay process used to produce sodium carbonate.

CO₂ + 2 NH₃ + 2 NaCl + H₂O → 2 NH₄Cl + Na₂CO₃

In addition to being the principal method for the manufacture of ammonium chloride, this method is used to minimize ammonia release in some industrial operations. Ammonium chloride is prepared commercially by combining ammonia (NH₃) with either hydrogen chloride (gas) or hydrochloric acid (water solution):

NH₃ + HCl → NH₄Cl

Ammonium chloride occurs naturally in volcanic regions, forming on volcanic rocks near fume-releasing vents (fumaroles). The crystals deposit directly from the gaseous state, and tend to be short-lived, as they dissolve easily in water.

Reactions

Ammonium chloride appears to sublime upon heating. However, this process is actually decomposition into ammonia and hydrogen chloride gas.

NH₄Cl → NH₃ + HCl

Ammonium chloride reacts with a strong base, e.g. sodium hydroxide, to release ammonia gas:

NH₄Cl + NaOH → NH₃ + NaCl + H₂O

Similarly, ammonium chloride also reacts with alkali metal carbonates at elevated temperatures, giving ammonia and alkali metal chloride:

2 NH₄Cl + Na₂CO₃ → 2 NaCl + CO₂ + H₂O + 2 NH₃

A 5% by weight solution of ammonium chloride in water has a pH in the range 4.6 to 6.0.

Applications

The main application of ammonium chloride is as a nitrogen source in fertilizers, e.g. chloroammonium phosphate. The main crops are rice and wheat in Asia.

Pyrotechnics

Ammonium chloride is an ingredient in fireworks, safety matches and contact explosives.

Metalwork

Ammonium chloride is used as a flux in preparing metals to be tin coated, galvanized or soldered. It works as a flux by cleaning the surface of workpieces by reacting with the metal oxides at the surface to form a volatile metal chloride. For this purpose, it is sold in blocks at hardware stores for use in cleaning the tip of a soldering iron and can also be included in solder as flux.

Medicine

Ammonium chloride is used as an expectorant in cough medicine. Its expectorant action is caused by irritative action on the bronchial mucosa. This causes the production of excess respiratory tract fluid which presumably is easier to cough up. Ammonium salts are an irritant to the gastric mucosa and may induce nausea and vomiting.

Ammonium chloride is used as a systemic acidifying agent in treatment of severe metabolic alkalosis, in oral acid loading test to diagnose distal renal tubular acidosis, to maintain the urine at an acid pH in the treatment of some urinary-tract disorders.

Food

In several countries, ammonium chloride, known as sal ammoniac, is used as food additive under the E number E510, commonly as a yeast nutrient in breadmaking. It is a feed supplement for cattle and an ingredient in nutritive media for yeasts and many microorganisms.

Ammonium chloride is used to spice up dark sweets called salty liquorice, in baking to give cookies a very crisp texture, and in the flavouring Salmiakki Koskenkorva for vodkas. In India and Pakistan, it is called nausader and is used to improve the crispiness of snacks such as samosas and jalebi.

In the laboratory

Ammonium chloride is used to produce low temperatures in cooling baths. Ammonium chloride solutions with ammonia are used as buffer solutions.

Other applications

Ammonium chloride is used in a ~5% aqueous solution to work on oil wells with clay swelling problems. It is also used as electrolyte in zinc–carbon batteries. Other uses include in hair shampoo, in the glue that bonds plywood, and in cleaning products. In hair shampoo, it is used as a thickening agent in ammonium-based surfactant systems, such as ammonium lauryl sulfate. Ammonium chloride is used in the textile and leather industry in dyeing, tanning, textile printing and to luster cotton.