Both double salts as well as complexes are formed by the combination of two or more stable compounds in stoichiometric ratio. However, double salts such as carnallite, KCl.MgCl2.6H2O, Mohr‘s salt, FeSO4.(NH4)2SO4.6H2O, potash alum, KAl(SO4)2.12H2O, etc. dissociate into simple ions completely when dissolved in water. However, complex ions such as [Fe(CN)6]4– of K4[Fe(CN)6], do not dissociate into Fe2+ and CN– ions.
