This crystallizes as the pale pink decahydrate Fe(ClO4)3.10H2O
from solutions of iron(III) chloride or hydrous iron(III) oxide in perchloric acid. Upon
standing over phosphorus pentoxide the decahydrate becomes the hexahydrate ; a 9-hydrate
crystallizes from solution above 42°. This salt has been important in the study of the
hydrated Fe3+ ion since perchlorate ions have only very low coordinating ability.
Purification Methods
Crystallise it twice from conc HClO4, the first time in the presence of a small amount of H2O2 to ensure that the iron is fully oxidised [Sullivan J Am Chem Soc 84 4256 1962]. Extreme care should be taken with this preparation because it is potentially EXPLOSIVE.
