Ammonium chloride, Ammonium tetraoxosulphate(VI), Ammonium trioxocarbonate(IV) and Ammonium trioxonitrate(V)

Ammonium salts are applicable to an array of everyday materials that range from fertilizers in agriculture through medical to military use. Here, we will be dealing with four examples of important ammonium salts that include ammonium chloride, ammonium tetraoxosulphate(VI), ammonium trioxocarbonate(IV) and ammonium trioxonitrate(V).

Ammonium chloride, NH₄Cl, is an important laboratory analytic reagent that is also used to ease the melting of solders during melting. Ammonium chloride is most valued as electrolyte for Leclanché
cell and our common everyday batteries (dry cell).

Ammonium chloride is a white crystalline solid that sublimes on heating. It is a non-hydrated salt that dissociates to hydrogen chloride gas and ammonia gas when heated for a long period of time.

(heat) NH₄Cl(s) ↔ NH₃(g) + HCl(g) (cold)

Ammonia and hydrogen chloride gas formed from heated ammonium chloride recombine when cooled to reform the ammonium chloride.

Ammonium tetraoxosulphate(VI), (NH₄)₂SO₄, is important in agriculture where it is used as fertilizer for crops and as a weed killer (herbicide).

The laboratory preparation of ammonium tetraoxosulphate(VI) is a simple neutralization reaction of dilute tetraoxosulphate(VI) acid with aqueous ammonia.

H₂SO₄(aq) + 2NH₄⁺ + 2OH^- ↔ (NH₄)₂SO₄(aq) + 2H₂O(l)

Ammonium tetraoxosulphate(VI) is prepared industrially from gypsum (calcium tetraoxosulphate(VI) dihydrate), CaSO₄.2H₂O, or from calcium tetraoxosulphate(VI) suspension. Ammonia with carbon(IV) oxide is passed through the sulphate to precipitate insoluble calcium trioxocarbonate(IV), CaCO₃, leaving soluble ammonium tetraoxosulphate(VI) in solution.

CaSO₄(s) + 2NH₃(g) + CO₂(g) + H₂O(l) → (NH₄)₂SO₄(aq) + CaCO₃(s)

The ammonium tetraoxosulphate(VI) salt can be obtained by crystallization.

Ammonium trioxocarbonate(IV) is another example of ammonium salt used as a laboratory analytical reagent. A remarkable use is to prevent dizziness and by extension, to trigger consciousness in smelling salts. Ammonium trioxocarbonate(IV) decomposes event at room temperature to liberate ammonia gas which irritates the mucous membrane of the nose and lungs to trigger inhalation reflex action. Smelling salts is also referred to as "spirit of hartshorn" or "sal volatile".

Ammonium trioxocarbonate(IV) is formed as a sublime from heating a mixture of calcium trioxocarbonate(IV) and ammonium tetraoxosulphate(VI).

(NH₄)₂SO₄(s) + CaCO₃(s) → (NH₄)₂CO₃(s) + CaSO₄(s)

The other products are calcium tetraoxosulphate(VI) and ammonium hydrogentrioxocarbonate(IV). The ammonium hydrogentrioxocarbonate(IV) is formed as a part of the sublimate, and the trioxocarbonate(IV) can be separated by the addition of ammonia to the sublimate.

Ammonium trioxonitrate(V), NH₄NO₃, is primarily used in agriculture as a fertilizer like nitrochalk fertilizer, and in the manufacture of explosives such as amatol or ammonal. A unique use is how it absorbs large amount of heat when dissolved in water. Here, the dissolved ammonium trioxonitrate(V) is used as a freezing mixture when large quantity is dissolved in water.

Ammonium trioxonitrate(V) is a colourless crystalline salt obtained from the crystallization from aqueous solution after a neutralization reaction between aqueous ammonia and trioxonitrate(V) acid.

NH₄⁺(aq) + OH^-(aq) HNO₃(aq) → NH₄NO₃(aq) + H₂O(l)