Ammonium chloride

Ammonium chloride is an inorganic compound with the formula NH4Cl and a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. In its naturally occurring mineralogic form, it is known as sal ammoniac. The mineral is commonly formed on burning coal dumps from condensation of coal-derived gases. It is also found around some types of volcanic vents. It is mainly used as fertilizer and a flavouring agent in some types of liquorice. It is the product from the reaction of hydrochloric acid and ammonia. It is a product of the Solvay process used to produce sodium carbonate: CO2 + 2 NH3 + 2 NaCl + H2O → 2 NH4Cl + Na2CO3 Not only is that method the principal one for the manufacture of ammonium chloride, but also it 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. Ammonium chloride appears to sublime upon heating but actually reversibly decomposes into ammonia and hydrogen chloride gas: NH4Cl NH3 + HCl Ammonium chloride reacts with a strong base, like 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 solution of 5% by mass of ammonium chloride in water has a pH in the range 4.6 to 6.0. Some reactions of ammonium chloride with other chemicals are endothermic, such as its reaction with barium hydroxide and its dissolving in water. The dominant application of ammonium chloride is as a nitrogen source in fertilizers (corresponding to 90% of the world production of ammonium chloride) such as chloroammonium phosphate.