Editing Ammonium (section)

== Salts and characteristic reactions ==
[[File:Bildung Ammonium.svg|thumb|Formation of ammonium]]
Ammonium cation is found in a variety of [[salt (chemistry)|salt]]s such as [[ammonium carbonate]], [[ammonium chloride]], and [[ammonium nitrate]]. Most simple ammonium salts are very [[soluble]] in water. An exception is [[ammonium hexachloroplatinate]], the formation of which was once used as a test for ammonium. The ammonium salts of nitrate and especially [[perchlorate]] are highly explosive, in these cases, ammonium is the reducing agent.

In an unusual process, ammonium ions form an [[amalgam (chemistry)|amalgam]]. Such species are prepared by the addition of sodium amalgam to a solution of ammonium chloride.<ref>{{Cite web |url=http://www.hull.ac.uk/chemistry/intro_inorganic/Chap9.htm |title=Pseudo-binary compounds |access-date=2007-10-12 |archive-date=2020-07-27 |archive-url=https://web.archive.org/web/20200727215402/https://www.hull.ac.uk/chemistry/intro_inorganic/Chap9.htm |url-status=dead }}</ref> This amalgam eventually decomposes to release ammonia and hydrogen.<ref>{{cite encyclopedia|encyclopedia = VIAS Encyclopedia|title = Ammonium Salts |url = http://www.vias.org/encyclopedia/chem_ammonia_salts.html}}</ref>

To find whether the ammonium ion is present in the salt, first, the salt is heated in presence of [[alkali hydroxide]] releasing a gas with a characteristic smell, which is [[ammonia]].
: {{chem2|[NH4]+ + OH-}} {{overset|''heat''|→}} {{chem2|NH3 + H2O}}

To further confirm ammonia, it is passed through a glass rod dipped in an {{Chem2|HCl}} solution ([[hydrochloric acid]]), creating white dense fumes of [[ammonium chloride]].
: {{chem2|NH3(g) + HCl(aq) → [NH4]Cl(s)}}

Ammonia, when passed through {{chem2|CuSO4}} ([[copper(II) sulfate]]) solution, changes its color from blue to deep blue, forming [[Schweizer's reagent]].
: {{chem2|CuSO4(aq) + 4 NH3(aq) + 4 H2O → [Cu(NH3)4(H2O)2](OH)2(aq) + H2SO4(aq)}}

Ammonia or ammonium ion when added to [[Nessler's reagent]] gives a brown color precipitate known as the iodide of Million's base in basic medium.

Ammonium ion when added to [[chloroplatinic acid]] gives a yellow precipitate of [[Ammonium hexachloroplatinate|ammonium hexachloroplatinate(IV)]].
: {{chem2|H2[PtCl6](aq) + [NH4]+(aq) → [NH4]2[PtCl6](s) + 2 H+}}

Ammonium ion when added to [[sodium cobaltinitrite]] gives a yellow precipitate of ammonium cobaltinitrite.
: {{chem2|Na3[Co(NO2)6](aq) + 3 [NH4]+(aq) → [NH4]3[Co(NO2)6](s) + 3 Na+(aq)}}

Ammonium ion gives a white precipitate of ammonium bitartrate when added to [[potassium bitartrate]].
: {{chem2|KC4H5O6(aq) + [NH4]+(aq) → [NH4]C4H5O6(s) + K+(aq)}}