Formation of a reddish brown ppt. with alkaline K2HgI4 solution indicates the presence of radical ammonium NH+4 and the gas liberated in ammonia. The reactions are as
On treatment with BaCl2, a white ppt. is formed which indicates the presence of sulphate anion (SO2-4 ) sparingly soluble in conc. HCl.
With K2Cr2O7 and conc. H2SO4 red vapours are evolved which indicates the presence of chloride ion (Cl-). The reaction is as
On treatment with potassium ferricyanide indicates the presence of ferrous ions.