Nessler's reagent K2[HgI4] when dropped into solvated ammonia results in the formation of a reddish brown precipitate known as 'Iodide of Millon's Base' and has a chemical formula H2NHgOHgI. This reaction can be represented as:
2K2[HgI4](aq)+NH4OH(aq)+3KOH(aq)→H2NHgOHgI(s)+7KI(aq)+3H2O(l)